Brocktoon

This is a little drive I took this afternoon:

This was a cross town drive on surface streets with stoplights, and a short, 3 exit burst on an expressway. Picture taken just before reaching my destination.

Stats: 23 km, 21 minutes, Average speed, 65 Km/h, fuel economy 9.1l/100km,
or 24.8mpg (us gal) 31mpg (imp gal).



Sorry about the pic, it's from my phone...

MomsBenz

Very nice! As diesel's break in it should keep getting better. I was pleased with our road trip I averaged 21.2 mpg in the 450 with the cargo carrier on top! Not too bad

StevethePilot

Very good for in-city driving! I've found my 320's stabilized at or near the 20/25 M/US Gal, with ~35,000 miles on it.

STP

dieseldoc

I am averaging 23 mpg combined driving on a GL320 with 3000 miles on it.

oknish

That is indeed great, Mom. While I haven't taken a 3K mile trip yet but the best I have seen is an occasional 21 MPG on way to Vegas.

MomsBenz

Gotta love cruise control. Ours was set at 80 mph there and back as the speed limit in Utah and Idaho is 75

grover432

The new one I test drove a while back showed 12.2L/100 KM over a day's driving in the city. Your mileage is much better than that. Perhaps it is the KM`s on your vehicle. How many have you racked up since you got you GL

Brocktoon

3600 km

occarfan

Wow. Never even come close to 20mpg yet.
Then again, never really leave Orange County with the SUV.

Brocktoon

I have been watching this like a hawk, and I have noticed that going up hills or idling when the engine is still cold, and blasting the A/C seem to have the largest negative impacts on mpg. I know that day in and out i will get 20% better ecomomy when I go to my parent's house up a gentle incline, than to my sister-in-law's place that is at a lower elevation, but up two steep hills....

lkchris

I'd venture that aerodynamics will be the biggest effect.

Got in a tailwind once in NE New Mexico and saw 29mpg on the dash while going 70. A few miles on, the wind had shifted a little more to the side and the number dropped to 23.

Pulled a trailer with motorcycle from NM to south TX and each fillup produced poorer mileage, I assume because as we lost altitude we were punching through "thicker" air. The engine electronics should adjust for the different air density but it can't change the amount of work the engine has to do.

Comfy_Couch

I averaged 22-23mpg with a cargo carrier on top during a recent road trip, with flat, straight highway driving all the way.

Brocktoon

Not in the city, man.

Yeah, but you get a denser charge, and more power per unit from the motor...

MomsBenz

Very Nice

lkchris

It's got a variable-pitch turbo--electronics determines the density.

scottybdiving

Density Altitude is the key. As the moisture and/or temperature goes up, the air becomes lighter. You would think that moist air would weigh more than dry air but not so. Very humid and hot air has a very high "density altitude".

An NHRA race in Houston can have a density altitude as high as a race in Denver, if the conditions are right (cool and dry in Denver vs very hot and humid in Houston) even though there's a 5000 VF difference.

Brocktoon

Pressure is not density.

You are 100% correct, but we have an intercooler that should fix the temp issue after the charge heats up from the turbo. A few degrees of ambient is nothing compared to the cooling that takes place overall. That's the point I was making to Ikcris, the turbo makes the pressure, in our case variable with vanes, and not only related to exhaust pressure, but the intercooler creates the density. He's likely right, in that altitude did not help him, but thinking this through, it likely was not the culprit either. As I said earlier, I have noticed that a blasting thermatic/thermotronic has a huge impact on the CDI so that's what I would look at going from NM to Tex....

Your milage may vary.

lkchris

The bottom line is that the fuel-air mixture is precisely controlled by the engine components and electronics and does not vary with altitude. The car burns more fuel at lower altitude because it is working harder and it takes more fuel to do more work.

StevethePilot

I don't know if the same principles apply to the diesel engines but I do know that one name for turbocharging in aircraft is "turbo-normalizing" or "normalization," the purpose of which is to give the same power to the engine at higher density altitudes (whether due to temperature, atmospheric pressure and dew point or actually being at a higher altitude) as it would get at a lower altitude, usually benchmarked at sea level on a standard day. For instance, in a turbocharged Cessna 182 I flew, I was able to maintain the same power to the engine from ~1500 feet (Scottsdale airpark) to I think 12,000 feet. This did not mean, however, there was no detriment to performance - the prop's still pulling through the air and that (as Kent pointed out) was thinner at altitude. In fact, the amount of the effect is noticeable as low as 5000 feet, though not huge.

Just my two bits on the subject!

Brocktoon

Right, so you "normaly" make more power at sea level, correct?

StevethePilot

Yes, without added atmosphere from turbocharging or supercharging (or both) (the difference between which is beyond moi).

STP

scottybdiving

You make more power at sea level, unless the water grains and temperature offset it, giving it a Density Altitude say equivalent to Denver. This is an ongoing concern for NHRA dragsters. Pomona, CA usually has the lowest density altitude in the country and that's where most of the records are set. There are other races near sea level, Houston and Gainesville, FL, but they have much higher density altitudes due to high humidity.

mortenmol

My gl 420 cdi after 25k Miles

Brocktoon

Are you kidding?

cgjungdds

mine doesnt even require fuel anymore
odd
it just keeps going??