Mpg
12-23-2011, 06:21 PM
#26
Junior Member
Join Date: Dec 2011
Posts: 66
Likes: 0
Received 0 Likes
on
0 Posts
GL450
I dont care about preformance as much as i care about MPG i drive about 10 miles a day on avg on weekend its more. I drive to/frok train station at the most 35mph i care much more about MPG and how much I can save at the pump. I guess ill jus have to try.
12-23-2011, 07:23 PM
#27
Senior Member
Join Date: Dec 2011
Location: Middlesex, NJ
Posts: 367
Likes: 0
Received 0 Likes
on
0 Posts
03 Nissan Altima 2.5S, 07 MB GL450
When I mention performance I meant by overall engine drivability which means "mpg".
And I meant to "say not lower than 91 octane" not 87 octane.
It's a lease for you. Try with whatever you like. Experiment.
And I meant to "say not lower than 91 octane" not 87 octane.
It's a lease for you. Try with whatever you like. Experiment.
12-23-2011, 07:30 PM
#28
Junior Member
Join Date: Dec 2011
Posts: 66
Likes: 0
Received 0 Likes
on
0 Posts
GL450
I don't wanna start the war. Everybody has their own opinion, but I know many people who lease GL/E classes and they put 87 with no problems at all.
Fortunately for me - there is no " 87 diesel " thing, so I have no choice, but my E class never sees 93 in NYC. I only put it when I'm in NJ, where it's about 40 cents cheaper.
Fortunately for me - there is no " 87 diesel " thing, so I have no choice, but my E class never sees 93 in NYC. I only put it when I'm in NJ, where it's about 40 cents cheaper.
12-23-2011, 08:15 PM
#29
Senior Member
Join Date: Sep 2007
Location: Minnesota
Posts: 362
Likes: 0
Received 0 Likes
on
0 Posts
2008 GL 320 CDI Black/Black
I really don't think in the driving conditions above you are going to notice any better or worse mileage. Careful how you treat it...I bought mine out of the lease last year because the residual was so low I'd have been stupid to turn it in.
12-23-2011, 11:03 PM
#31
Newbie
Join Date: Dec 2011
Posts: 4
Likes: 0
Received 0 Likes
on
0 Posts
straight from wikipedia
Effects of octane rating
Higher octane ratings correlate to higher activation energies: This being the amount of applied energy required to initiate combustion. Since higher octane fuels have higher activation energy requirements, it is less likely that a given compression will cause uncontrolled ignition, otherwise known as autoignition or detonation.
It might seem odd that fuels with higher octane ratings are used in more powerful engines, since such fuels ignite less easily. However, detonation is undesirable in a spark ignition engine, and is signified by audible "pinging" or in more extreme cases "knock".
A fuel with a higher octane rating can be burnt in an engine with a high compression ratio without causing detonation, as such fuels are less prone to detonation. Compression is directly related to power and to thermodynamic efficiency (see engine tuning), so engines that require a higher octane fuel usually develop more motive power and therefore do more work in relation to the calorific value of the fuel (BTU) being used. Power output is a function of the properties of the fuel used, as well as the design of the engine itself, and is related to octane rating of the fuel. Power is limited by the maximum amount of fuel-air mixture that can be brought into the combustion chamber. When the throttle is partly open, only a small fraction of the total available power is produced because the manifold is operating at pressures far below that of the external atmosphere (depression). In this case, the octane requirement is far lower than when the throttle is opened fully and the manifold pressure increases to almost that of the external atmosphere, or higher in the case of forced induction engines (See supercharged or turbocharged engines).
Many high-performance engines are designed to operate with a high maximum compression, and thus demand fuels of higher octane. A common misconception is that power output or fuel efficiency can be improved by burning fuel of higher octane than that specified by the engine manufacturer. The power output of an engine depends in part on the energy density of the fuel being burnt. Fuels of different octane ratings may have similar densities, but because switching to a higher octane fuel does not add more hydrocarbon content or oxygen, the engine cannot develop more power.
However, burning fuel with a lower octane rating than that for which the engine is designed often results in a reduction of power output and efficiency. Many modern engines are equipped with a knock sensor (a small piezoelectric microphone), which sends a signal to the engine control unit, which in turn retards the ignition timing when detonation is detected. Retarding the ignition timing reduces the tendency of the fuel-air mixture to detonate, but also reduces power output and fuel efficiency. Because of this, under conditions of high load and high temperature, a given engine may have a more consistent power output with a higher octane fuel, as such fuels are less prone to detonation. Some modern high performance engines are actually optimized for higher than pump premium (93 AKI in the US). The 2001 - 2007 BMW M3 with the S54 engine is one such car. Car and Driver magazine tested a car using a dynamometer, and found that the power output increased as the AKI was increased up to approximately 96 AKI.
Most fuel filling stations have two storage tanks (even those offering 3 or 4 octane levels): those motorists who purchase intermediate grade fuels are given a mixture of higher and lower octane fuels. "Premium" grade is fuel of higher octane, and the minimum grade sold is fuel of lower octane. Purchasing 91 octane fuel (where offered) simply means that more fuel of higher octane is blended with commensurately less fuel of lower octane, than when purchasing a lower grade. The detergents and other additives in the fuel are often, but not always, identical.
The octane rating was developed by chemist Russell Marker at the Ethyl Corporation in 1926. The selection of n-heptane as the zero point of the scale was due to its availability in high purity. Other isomers of heptane produced from crude oil have greatly different ratings
Higher octane ratings correlate to higher activation energies: This being the amount of applied energy required to initiate combustion. Since higher octane fuels have higher activation energy requirements, it is less likely that a given compression will cause uncontrolled ignition, otherwise known as autoignition or detonation.
It might seem odd that fuels with higher octane ratings are used in more powerful engines, since such fuels ignite less easily. However, detonation is undesirable in a spark ignition engine, and is signified by audible "pinging" or in more extreme cases "knock".
A fuel with a higher octane rating can be burnt in an engine with a high compression ratio without causing detonation, as such fuels are less prone to detonation. Compression is directly related to power and to thermodynamic efficiency (see engine tuning), so engines that require a higher octane fuel usually develop more motive power and therefore do more work in relation to the calorific value of the fuel (BTU) being used. Power output is a function of the properties of the fuel used, as well as the design of the engine itself, and is related to octane rating of the fuel. Power is limited by the maximum amount of fuel-air mixture that can be brought into the combustion chamber. When the throttle is partly open, only a small fraction of the total available power is produced because the manifold is operating at pressures far below that of the external atmosphere (depression). In this case, the octane requirement is far lower than when the throttle is opened fully and the manifold pressure increases to almost that of the external atmosphere, or higher in the case of forced induction engines (See supercharged or turbocharged engines).
Many high-performance engines are designed to operate with a high maximum compression, and thus demand fuels of higher octane. A common misconception is that power output or fuel efficiency can be improved by burning fuel of higher octane than that specified by the engine manufacturer. The power output of an engine depends in part on the energy density of the fuel being burnt. Fuels of different octane ratings may have similar densities, but because switching to a higher octane fuel does not add more hydrocarbon content or oxygen, the engine cannot develop more power.
However, burning fuel with a lower octane rating than that for which the engine is designed often results in a reduction of power output and efficiency. Many modern engines are equipped with a knock sensor (a small piezoelectric microphone), which sends a signal to the engine control unit, which in turn retards the ignition timing when detonation is detected. Retarding the ignition timing reduces the tendency of the fuel-air mixture to detonate, but also reduces power output and fuel efficiency. Because of this, under conditions of high load and high temperature, a given engine may have a more consistent power output with a higher octane fuel, as such fuels are less prone to detonation. Some modern high performance engines are actually optimized for higher than pump premium (93 AKI in the US). The 2001 - 2007 BMW M3 with the S54 engine is one such car. Car and Driver magazine tested a car using a dynamometer, and found that the power output increased as the AKI was increased up to approximately 96 AKI.
Most fuel filling stations have two storage tanks (even those offering 3 or 4 octane levels): those motorists who purchase intermediate grade fuels are given a mixture of higher and lower octane fuels. "Premium" grade is fuel of higher octane, and the minimum grade sold is fuel of lower octane. Purchasing 91 octane fuel (where offered) simply means that more fuel of higher octane is blended with commensurately less fuel of lower octane, than when purchasing a lower grade. The detergents and other additives in the fuel are often, but not always, identical.
The octane rating was developed by chemist Russell Marker at the Ethyl Corporation in 1926. The selection of n-heptane as the zero point of the scale was due to its availability in high purity. Other isomers of heptane produced from crude oil have greatly different ratings
12-24-2011, 10:41 AM
#32
Junior Member
Join Date: Dec 2011
Posts: 66
Likes: 0
Received 0 Likes
on
0 Posts
GL450
Effects of octane rating
Higher octane ratings correlate to higher activation energies: This being the amount of applied energy required to initiate combustion. Since higher octane fuels have higher activation energy requirements, it is less likely that a given compression will cause uncontrolled ignition, otherwise known as autoignition or detonation.
It might seem odd that fuels with higher octane ratings are used in more powerful engines, since such fuels ignite less easily. However, detonation is undesirable in a spark ignition engine, and is signified by audible "pinging" or in more extreme cases "knock".
A fuel with a higher octane rating can be burnt in an engine with a high compression ratio without causing detonation, as such fuels are less prone to detonation. Compression is directly related to power and to thermodynamic efficiency (see engine tuning), so engines that require a higher octane fuel usually develop more motive power and therefore do more work in relation to the calorific value of the fuel (BTU) being used. Power output is a function of the properties of the fuel used, as well as the design of the engine itself, and is related to octane rating of the fuel. Power is limited by the maximum amount of fuel-air mixture that can be brought into the combustion chamber. When the throttle is partly open, only a small fraction of the total available power is produced because the manifold is operating at pressures far below that of the external atmosphere (depression). In this case, the octane requirement is far lower than when the throttle is opened fully and the manifold pressure increases to almost that of the external atmosphere, or higher in the case of forced induction engines (See supercharged or turbocharged engines).
Many high-performance engines are designed to operate with a high maximum compression, and thus demand fuels of higher octane. A common misconception is that power output or fuel efficiency can be improved by burning fuel of higher octane than that specified by the engine manufacturer. The power output of an engine depends in part on the energy density of the fuel being burnt. Fuels of different octane ratings may have similar densities, but because switching to a higher octane fuel does not add more hydrocarbon content or oxygen, the engine cannot develop more power.
However, burning fuel with a lower octane rating than that for which the engine is designed often results in a reduction of power output and efficiency. Many modern engines are equipped with a knock sensor (a small piezoelectric microphone), which sends a signal to the engine control unit, which in turn retards the ignition timing when detonation is detected. Retarding the ignition timing reduces the tendency of the fuel-air mixture to detonate, but also reduces power output and fuel efficiency. Because of this, under conditions of high load and high temperature, a given engine may have a more consistent power output with a higher octane fuel, as such fuels are less prone to detonation. Some modern high performance engines are actually optimized for higher than pump premium (93 AKI in the US). The 2001 - 2007 BMW M3 with the S54 engine is one such car. Car and Driver magazine tested a car using a dynamometer, and found that the power output increased as the AKI was increased up to approximately 96 AKI.
Most fuel filling stations have two storage tanks (even those offering 3 or 4 octane levels): those motorists who purchase intermediate grade fuels are given a mixture of higher and lower octane fuels. "Premium" grade is fuel of higher octane, and the minimum grade sold is fuel of lower octane. Purchasing 91 octane fuel (where offered) simply means that more fuel of higher octane is blended with commensurately less fuel of lower octane, than when purchasing a lower grade. The detergents and other additives in the fuel are often, but not always, identical.
The octane rating was developed by chemist Russell Marker at the Ethyl Corporation in 1926. The selection of n-heptane as the zero point of the scale was due to its availability in high purity. Other isomers of heptane produced from crude oil have greatly different ratings
Higher octane ratings correlate to higher activation energies: This being the amount of applied energy required to initiate combustion. Since higher octane fuels have higher activation energy requirements, it is less likely that a given compression will cause uncontrolled ignition, otherwise known as autoignition or detonation.
It might seem odd that fuels with higher octane ratings are used in more powerful engines, since such fuels ignite less easily. However, detonation is undesirable in a spark ignition engine, and is signified by audible "pinging" or in more extreme cases "knock".
A fuel with a higher octane rating can be burnt in an engine with a high compression ratio without causing detonation, as such fuels are less prone to detonation. Compression is directly related to power and to thermodynamic efficiency (see engine tuning), so engines that require a higher octane fuel usually develop more motive power and therefore do more work in relation to the calorific value of the fuel (BTU) being used. Power output is a function of the properties of the fuel used, as well as the design of the engine itself, and is related to octane rating of the fuel. Power is limited by the maximum amount of fuel-air mixture that can be brought into the combustion chamber. When the throttle is partly open, only a small fraction of the total available power is produced because the manifold is operating at pressures far below that of the external atmosphere (depression). In this case, the octane requirement is far lower than when the throttle is opened fully and the manifold pressure increases to almost that of the external atmosphere, or higher in the case of forced induction engines (See supercharged or turbocharged engines).
Many high-performance engines are designed to operate with a high maximum compression, and thus demand fuels of higher octane. A common misconception is that power output or fuel efficiency can be improved by burning fuel of higher octane than that specified by the engine manufacturer. The power output of an engine depends in part on the energy density of the fuel being burnt. Fuels of different octane ratings may have similar densities, but because switching to a higher octane fuel does not add more hydrocarbon content or oxygen, the engine cannot develop more power.
However, burning fuel with a lower octane rating than that for which the engine is designed often results in a reduction of power output and efficiency. Many modern engines are equipped with a knock sensor (a small piezoelectric microphone), which sends a signal to the engine control unit, which in turn retards the ignition timing when detonation is detected. Retarding the ignition timing reduces the tendency of the fuel-air mixture to detonate, but also reduces power output and fuel efficiency. Because of this, under conditions of high load and high temperature, a given engine may have a more consistent power output with a higher octane fuel, as such fuels are less prone to detonation. Some modern high performance engines are actually optimized for higher than pump premium (93 AKI in the US). The 2001 - 2007 BMW M3 with the S54 engine is one such car. Car and Driver magazine tested a car using a dynamometer, and found that the power output increased as the AKI was increased up to approximately 96 AKI.
Most fuel filling stations have two storage tanks (even those offering 3 or 4 octane levels): those motorists who purchase intermediate grade fuels are given a mixture of higher and lower octane fuels. "Premium" grade is fuel of higher octane, and the minimum grade sold is fuel of lower octane. Purchasing 91 octane fuel (where offered) simply means that more fuel of higher octane is blended with commensurately less fuel of lower octane, than when purchasing a lower grade. The detergents and other additives in the fuel are often, but not always, identical.
The octane rating was developed by chemist Russell Marker at the Ethyl Corporation in 1926. The selection of n-heptane as the zero point of the scale was due to its availability in high purity. Other isomers of heptane produced from crude oil have greatly different ratings
12-24-2011, 01:44 PM
#33
Senior Member
Join Date: Dec 2011
Location: Middlesex, NJ
Posts: 367
Likes: 0
Received 0 Likes
on
0 Posts
03 Nissan Altima 2.5S, 07 MB GL450
12-24-2011, 03:02 PM
#35
Senior Member
Join Date: Dec 2011
Location: Middlesex, NJ
Posts: 367
Likes: 0
Received 0 Likes
on
0 Posts
03 Nissan Altima 2.5S, 07 MB GL450
...which I actually did try to explain in terms of "ECU pulling timing and reduced engine performance and mpg"
Whoopsee if my explanation wasn't half a page long. But you should've gotten the general idea. Usually people write "TL;DR which stands for too long didn't read" but mine it was probably "TS;DR for TOO SHORT didn't read".
Whoopsee if my explanation wasn't half a page long. But you should've gotten the general idea. Usually people write "TL;DR which stands for too long didn't read" but mine it was probably "TS;DR for TOO SHORT didn't read".
12-24-2011, 03:56 PM
#36
Junior Member
Join Date: Dec 2011
Posts: 66
Likes: 0
Received 0 Likes
on
0 Posts
GL450
...which I actually did try to explain in terms of "ECU pulling timing and reduced engine performance and mpg"
Whoopsee if my explanation wasn't half a page long. But you should've gotten the general idea. Usually people write "TL;DR which stands for too long didn't read" but mine it was probably "TS;DR for TOO SHORT didn't read".
Whoopsee if my explanation wasn't half a page long. But you should've gotten the general idea. Usually people write "TL;DR which stands for too long didn't read" but mine it was probably "TS;DR for TOO SHORT didn't read".
12-30-2011, 04:57 PM
#37
Newbie
Join Date: Feb 2010
Location: Bedford, NY
Posts: 2
Likes: 0
Received 0 Likes
on
0 Posts
2010 e350 Sport 4matic
octane and fuel economy
i've tried going from 87 to 91 and even 93 in my 2011 e-class and my wife's 2007 lr3. driving very similar conditions, I have noticed no difference in performance and/or fuel economy. certainly not enough to justify the price difference here in NY (40 cents/gallon).
we just picked up a 2012 gl - you better believe she'll be drinking 87.
i've spoken with mechanics, engineers, etc about this very topic. some acknowledge the concept that the ecu could detect knock, downgrade performance, etc, etc. but my experience tells me the octane difference is not substantial enough to change anything.
should be a mythbusters topic i suppose....
seth
we just picked up a 2012 gl - you better believe she'll be drinking 87.
i've spoken with mechanics, engineers, etc about this very topic. some acknowledge the concept that the ecu could detect knock, downgrade performance, etc, etc. but my experience tells me the octane difference is not substantial enough to change anything.
should be a mythbusters topic i suppose....
seth
12-30-2011, 06:33 PM
#38
Super Member
01-09-2012, 06:12 PM
#39
PLATINUM SPONSOR
i've tried going from 87 to 91 and even 93 in my 2011 e-class and my wife's 2007 lr3. driving very similar conditions, I have noticed no difference in performance and/or fuel economy. certainly not enough to justify the price difference here in NY (40 cents/gallon).
we just picked up a 2012 gl - you better believe she'll be drinking 87.
i've spoken with mechanics, engineers, etc about this very topic. some acknowledge the concept that the ecu could detect knock, downgrade performance, etc, etc. but my experience tells me the octane difference is not substantial enough to change anything.
should be a mythbusters topic i suppose....
seth
we just picked up a 2012 gl - you better believe she'll be drinking 87.
i've spoken with mechanics, engineers, etc about this very topic. some acknowledge the concept that the ecu could detect knock, downgrade performance, etc, etc. but my experience tells me the octane difference is not substantial enough to change anything.
should be a mythbusters topic i suppose....
seth
I have to agree , as long as you are not towing or racing (open loop mode). The MPG does not matter a whole lot then anyway.. .
At hwy cruise or part throttle, 87 to 91 and 93 , I would say 87 will give better MPG, as load is low and 87 octane has more energy per bang than higher octane. Under load, even medium throttle and wide open throttle, timing will be pulled, knock may cause some slow damage and average MPG will drop. Also less additives in reg. fuel VS premium, so in the long run, it may cost you anyway. If I was doing all city driving, I would not run 87 octane on a premium designed engine.
__________________
E63 Biturbo, UPD Cold Air induction kit, UPD performance crank pulley and UPD adjustable rear suspension with ride height adjustment.
CL55 UPD Cold Air Boost kit, UPD 3000 stall converter, UPD 77mm SC clutched pulley and beltwrap kit, Custom long tubes, UPD crank pulley , UPD suspension kit, UPD SC pulley, Aux. HE, Trunk tank w/rule 2000 pump, Mezeire pump, UPD 5pc idler set, Aluminum rotor hats.
www.ultimatepd.com
instagram @ultimate_pd
facebook.com/ultimatepd
E63 Biturbo, UPD Cold Air induction kit, UPD performance crank pulley and UPD adjustable rear suspension with ride height adjustment.
CL55 UPD Cold Air Boost kit, UPD 3000 stall converter, UPD 77mm SC clutched pulley and beltwrap kit, Custom long tubes, UPD crank pulley , UPD suspension kit, UPD SC pulley, Aux. HE, Trunk tank w/rule 2000 pump, Mezeire pump, UPD 5pc idler set, Aluminum rotor hats.
www.ultimatepd.com
instagram @ultimate_pd
facebook.com/ultimatepd
01-10-2012, 03:41 PM
#40
Senior Member
Join Date: Oct 2010
Location: SoCal
Posts: 260
Likes: 0
Received 0 Likes
on
0 Posts
Porsche 911
As it relates to this...
I did a cross-country trip from CA to OK about a year ago. I was averaging 18.5-19 mpg across AZ, NM & TX at speeds of 80-100mph. When I gassed up in TX before the OK border they only had 87 or 89 instead of the 93 I had been using. The next leg of the journey I could not get mileage above 17.5-18 mpg. All other factors seemed about the same. If anything, I may have slowed down to 75-85mph due to the OK troopers being a bit more aggressive than those in NM & TX!
I did a cross-country trip from CA to OK about a year ago. I was averaging 18.5-19 mpg across AZ, NM & TX at speeds of 80-100mph. When I gassed up in TX before the OK border they only had 87 or 89 instead of the 93 I had been using. The next leg of the journey I could not get mileage above 17.5-18 mpg. All other factors seemed about the same. If anything, I may have slowed down to 75-85mph due to the OK troopers being a bit more aggressive than those in NM & TX!
02-25-2012, 06:28 AM
#41
Junior Member
something is very screwy...
my trip comp has been saying i'm between 25-26 mpg... but my calcs are all screwy...
Vegas trip 487 miles - 22.853 gal - calc is 21.3 mpg vs computer 25.1 mpg
Business trip 505 miles - 22.432 gal - cal is 22.4 mpg vs computer 23.2 mpg
Whats wrong with their computer?
my trip comp has been saying i'm between 25-26 mpg... but my calcs are all screwy...
Vegas trip 487 miles - 22.853 gal - calc is 21.3 mpg vs computer 25.1 mpg
Business trip 505 miles - 22.432 gal - cal is 22.4 mpg vs computer 23.2 mpg
Whats wrong with their computer?
02-25-2012, 09:51 AM
#42
MBWorld Fanatic!
something is very screwy...
my trip comp has been saying i'm between 25-26 mpg... but my calcs are all screwy...
Vegas trip 487 miles - 22.853 gal - calc is 21.3 mpg vs computer 25.1 mpg
Business trip 505 miles - 22.432 gal - cal is 22.4 mpg vs computer 23.2 mpg
Whats wrong with their computer?
my trip comp has been saying i'm between 25-26 mpg... but my calcs are all screwy...
Vegas trip 487 miles - 22.853 gal - calc is 21.3 mpg vs computer 25.1 mpg
Business trip 505 miles - 22.432 gal - cal is 22.4 mpg vs computer 23.2 mpg
Whats wrong with their computer?
I drove last week from NYC to Orlando FL and my computer says 25.5. My average speed on computer is 67mph. I was driving about 80mph all the way. Got a ticket in VA for that
. Today I'm driving back.
02-25-2012, 08:42 PM
#43
Junior Member
Here is my rationale...
Always fill your tanks high as you can without topping off (Sometimes your fill will stop exactly at $100 depending on your credit card... trust me... there's more space if you were close to E). Reset your computer and note the data
Then at every fill up note the miles traveled from the last reset (=M). Also, look at the amount of gas you added to the tank (=G).
Then it's a simple calculation. M/G or mpg...
key is to fill your tank until it clicks off
Just filled my tank again today... ugh had to fill it twice because 1st fill hit $100
528 miles
1st fill (21.934gal) + 2nd fill (4.515 gal) = 26.449 gal
MPG Computer = 25.4 mpg
Actual Calculation = 19.96 mpg
Highest computer mpg and lowest actual mpg to date (only three fill ups since purchase)
Paid $4.56 per gallon today and $4.44 two days earlier from same station (Chevron)
Thanks Obama!
Greetings from Commiefornia!
Always fill your tanks high as you can without topping off (Sometimes your fill will stop exactly at $100 depending on your credit card... trust me... there's more space if you were close to E). Reset your computer and note the data
Then at every fill up note the miles traveled from the last reset (=M). Also, look at the amount of gas you added to the tank (=G).
Then it's a simple calculation. M/G or mpg...
key is to fill your tank until it clicks off
Just filled my tank again today... ugh had to fill it twice because 1st fill hit $100
528 miles
1st fill (21.934gal) + 2nd fill (4.515 gal) = 26.449 gal
MPG Computer = 25.4 mpg
Actual Calculation = 19.96 mpg
Highest computer mpg and lowest actual mpg to date (only three fill ups since purchase)
Paid $4.56 per gallon today and $4.44 two days earlier from same station (Chevron)
Thanks Obama!
Greetings from Commiefornia!
02-25-2012, 09:03 PM
#44
Super Member
Something really IS screwy! This is a GL forum and according to your profile, you drive a c63. As far as I know a c63 is a gasser and gassers have different requirements (much more difficult) for achieving a 'good' fill in order to accurately calculate mileage.
02-25-2012, 09:27 PM
#45
Junior Member
Sorry. Didnt update the profile. Just sold the turbo and traded the c63 for the GL350.
02-27-2012, 04:14 PM
#47
Senior Member
Join Date: Dec 2011
Location: Middlesex, NJ
Posts: 367
Likes: 0
Received 0 Likes
on
0 Posts
03 Nissan Altima 2.5S, 07 MB GL450
02-27-2012, 07:37 PM
#48
Super Member
In order to maximize accuracy, the fuel tank must be filled to EXACTLY the same point each time it is filled. Merely filling until the nozzle trips off the first (or second) time is not nearly precise enough because the amount of foam the diesel makes varies a lot and more foam means less fuel is delivered. This is GOOD for apparent mileage on the current tank [less fuel used] but BAD for the next tank since the smaller amount of fuel won't go as far.
Therefore, ALWAYS wait for the foam to subside - this may take a few minutes - and SLOWLY, at the SLOWEST nozzle opening you can manage, fill the tank TO THE EDGE OF THE FILLER NECK.
After you do that once, the NEXT fill up, which you do the same way, provides the number of gallons (or Liters) to use in the REAL mileage calculation. USE THAT number to compare with what the car computer says. Most M-B fuel computers read a couple of mpg higher than the REAL mileage although that varies.
Do NOT use this method to calculate mpg for gas fueled cars. Most have vapor canisters (emissions control system stuff) attached near the top of the filler tube. If those canisters get filled with raw gas, the car can go into 'limp' mode and may shut down completely because the vapor isn't vapor any more and can't be cycled back into the intake manifold. They are DESIGNED to do that!
