2slowcdi

My heads up display goes from almost right to over two miles per gallon off on average.
Another thing is Ethanol , some areas may not have it and they would get better mileage..
Places that have ethanol can take off 5 to 10% in their mileage.

Vik888

The reason you're seeing 24mpg and I can get 28mpg+ is because of the transmission. The 7G transmission in the E550 is whats generating those numbers. The E500 and the E550 are totally different cars in regards to the engine and transmission.

There are actually tons of threads on this forum w/ E550 figures from dozens of owners. Everyone can't be cook'n the books

MercFiveHundred

I've gotten 26-27mpg on my 03 e500. That's driving 50miles each way (total 100 miles), windows up, behind others in the middle lane, 55-60-65mph(incline/decline), not on cruise, outside temp around 75 degrees F, 99% highway. One warmer morning, i got 30mpg driving one way, but from Westchester to the Bronx (mostly a decline).

2slowcdi

The final drive numbers are not much different between the cars with the five speed transmission and with the seven speed transmission.
So it has to be the motor that change the mileage.

If people are going off the cars mileage display and not fill up's and real numbers that will be most of the problem.

I have never seen one on the money yet. I filled up today and mine was off -.8 miles per gallon so
it showed 29.9 to the real 29.1 mph that it was.

I check mine everytime.

Henrik

The final drive might not differ that much.. but the 7:th gear in the gearbox differs...
In the 7-speed gearbox the 5:th is 1:1 with both 6:th and 7:th being overdrives.

OK55

Depends on a number of things. At low speeds (say, below 35 mph) rolling resistance is pre-eminent. Beyond 35 mph (circa) drag comes into play. Typically steady speed fuel consumption will improve up to a peak not far from 35mph and worsen thereafter. The precise figure will depend on engine/ transmission characteristics et al. All things being equal, 55 mph should give better mileage per gallon than 60, 65, or 70.

I get circa 7.3 mpg in bad traffic and around 13.7 mpg on the highway...seem to have a bit of a lead foot...!
Brgds * *

OK55

You've certainly got a point there but I'd like to remind us that the e550 was sold in Europe as the e500.

Brgds

OK55

Possibly, but you're assuming the the filling station gauges are all accurate. They vary substantially in accuracy. Can't recall the US limit but some countries allow up to 10 percent variation...
Brgds

2slowcdi

I fill up at one pump at two different stations so I have the same numbers from time to time.
Most pumps are set low but the low is less that 6oz's in five gallons.
If you have every seen the red looking 5 gallon milk jug with the glass window at the top to make sure that the pumps are set its not much one way or the other.
One of my first jobs years ago I would calibrate gas pumps , you could get in just as much trouble for a pump that was giving to much gas as to little.

2slowcdi

The seventh gear along with the diff gears will give the same final drive ratio within a few percent of the over drive of the five speed transmission with the rear end gear ratio that the five speed cars have.
This is the case with most cars its to keep the rpm in the Sweet spot for the motor.

The easy to see is with the same tires and same air pressure the rpm at a given speed will be almost the same.

Henrik

E500 7-speed 388hp 7th gear 0,73, rear axle 2.47.
E500 5-speed 306hp 5th gear 0,83, rear axle 2.82.

(European versions.)

Can't find the rear axle ratio of the 306hp E500 7-speed though..
Nevertheless.. The newer engines are turning at a lower rpm according to the above..

OK55

I'll defer to you on the US figures but the difference between 29.1 mpg (from pumps and yr odometer), and 29.9 mpg (from yr vehicle computer) is about 2.7%.

An error of 6 ounces in 5 gallons dispensed by pumps is about 1%. And since this doesn't take into account the effect of temperature changes - a 13 deg C change could change petrol volume by up to 0.5% - I believe the total possible error is significant in comparison with the 2.7% difference.
Brgds

2slowcdi

I looked up the transmissions to see what was different and I was wrong on most of the seven speeds I found that
1st 4.39 ,,,,,,,,,,,,five speed
2nd 2.83 ,,,,,,,,,,,,1st 3.59
3rd 1.92 ,,,,,,,,,,,,,2nd 2.19
4th 1.37 ,,,,,,,,,,,,,3rd 1.41
5th 1.00 ,,,,,,,,,,,,,4th 1.00
6th .82 ,,,,,,,,,,,,,,,5th .83
7th .73 ,,,,,,,,,,,,,,,,Axle ratio
Axle ratio ,,,,,,,,,,,,,2.62
2.47

I had only looked at the AMG E55 and the E320 CDI five speeds and found one difference first gear, on the AMG its 3.59 and on the CDI its 3.60 everything else was the same.
So after looking at the AMG E55 gasser and the CDI diesel ,,,, I should have looked further.
So it looks like all the 7 speed transmissions are geared higher.
And this will help in mileage.
I got my diesel for reilability and longevity not mileage , but it does not hurt to get better mileage.

Dexion

65mph is definitely my sweet spot, I get 28mpg on my E320 RWD (I should probably be doing better I'll check after I do my spark plugs and air filter.) 70+mph and the mpgs drop.

slammer111

I thought North American cars get tuned differently (in terms of gearing) than ROW?

To answer this question from an engineering perspective, what we would need is a graph of the efficiency of the engine as a function of RPM, as well as aerodynamic data of the car. Slower is not always better once you factor this in. If we wanted to get all technical, I'd also ask for drivetrain losses as a function of tranny speed / gearing.

Actually that's when your car gets the WORST efficiency. You can idle your car to Empty before going 1m.

PlatinumPi4u

Here is what I learned from the interwebs:

The best MPG is going to come when the graph on the dyno has a flat tq and hp line.... so we would have to look at the stock dyno chart for our cars to see where exactly that sweet spot is.....

Anybody got a stock dyno chart for a w211 e500 ?

Speedriven1

Engine is most efficient at peak torque.

PlatinumPi4u

It appears I should be smashing it at 2700 rpms (city daily driving), but i'm not so sure about that.....

fmanfrank

I did want to add a sight note. Nothing to do with what MPH I was on, but on average (city/highway), I was at 20MPG when i switched to 91 oct. over the 17MPG that I used to get on 93 oct. I just switched to 91 about 2 fuel stops ago...

WHY on earth didn't I make this move before

Heatwave

Unless you're driving extended distances at a constant speed, your mileage results will always vary. Having gotten that out of the way, I can report that I've gotten best mileage ... about 29.1 - 29.3 mpg ... at a steady 75 on long interstate trips. Would it have been better had I driven a steady 55?--Perhaps ... but I ain't driving 55.

Oh ... this is in an E350.

PlatinumPi4u

I'm looking for flat lines on a dyno sheet..... those flat curves are the key - the flatter, the more bang for the buck the car is going to get..... anybody have a stock dyno chart so we can identify the flat curve?

(.....i'm not driving 55mph either!! ...but I don't want to be measuring my gas milage by the foot either...)

MEDICUS

OK everything relates to location and how long between slowing up. I had a car in ohio that was always around 25-27mpg when I moved to North Carolina I was averaging 38-43 and that was with 125,000 miles. See the thing is that in NC once you start moving you barely have to stop so you don't waste fuel. Back to the mercedes. In hawaii I average about 20 due to the mountains and constant stops. I found that the sweet spot for the car in hawaii is 45mph I average 25+mpg. in past experiences 70+ was always the sweet spot. Don't race up to it but keep it around 70+ and you will get the best MPG

Thom99

My experience is running at steady speeds between 65 to 75 on the interstates produces the best mileage. So far the best mileage I've gotten is 35.5 mpg and I'm due for the B service so air and fuel filters probably need changing or cleaning.



Thom

skiahh

Zero is not the correct answer. Zero, with the engine off, perhaps, but zero MPH with the engine running is 0 MPG. As noted, you can run your tank dry by going zero MPH.

As for MPH vs MPG, I'm not sure where the sweet spot in my car falls, but at 84 MPH, I'm around 40 MPG. I've started at 33.8 (where the computer defaults) and watched it climb to over 40; my last trip ended at 40.3 MPG on the display.

I've found the displayed figure to be a tad optimistic by 1-2 MPG based on hand calculations, though.

I haven't actually tested this, but when I run at 75, the computer seems to settle out closer to 38... so it just makes me wonder how the thing calculates the MPG since I doubt there's an inline flowmeter in the fuel system.

PlatinumPi4u

again, by examining the stock dyno chart to see where the flat curve is for each model of car, this will illustrate where the "sweet spot" is.... Am I right??