My First MPG Data Point - PeachParts Mercedes-Benz Forum

tarbe · #1 12-23-2006, 11:04 PM

Now that I have an operational odometer and have determined the error (it reads 5% short of actual), I figured it was time to start gathering mileage data.

I always fill (slowly) to the brim to eliminate errors from stopping short or leaving air in the tank.

500 miles: 300 were Houston commuting, including some horrible 45 minute long 12 miles trips to and from work. 50 miles of what I call "town and country" which is moderate speed (40 - 50mph), a few stops but not heavy traffic. Finally, 150 miles on I-10 at 60 - 62mph. 16.02 gallons for 31.2mpg. The current tank (350 miles so far) is looking similar...actually just a bit better as it has a higher percentage of highway driving.

I use 1 oz Power Service per 2 gallons dino diesel, and I drive like an old lady. I am also using Mobil 1 ATF and Mobil 1 gear lube. Dino 15W-40 Rotella currently in the engine, with a dose of AutoRx doing its thing. Have not touched the wheel bearings, yet.

How does this compare to other's mileage?

Tim

#2 12-23-2006, 11:35 PM

Heck of alot better than my 23mpg.

tarbe · #3 12-23-2006, 11:37 PM

I imagine my being at sea level makes quite a difference vs you being at 5000+ feet??

#4 12-23-2006, 11:43 PM

It might also have something to do with you having almost 200K less miles on your engine (My engine has roughly 380K miles).

GREASY_BEAST · #5 12-24-2006, 03:54 PM

I too get about 23mpg in my '84 300TD. I also have somewhere near 370-380K mi (estimated.. odometer never worked right since I got it and it read 350K when it broke). However, my car lacks an ALDA (not missed) and I flog it hard with Rotella 15-40 (synthetic too expensive right now.. gotta sort out all the little leaks first). 30ish mpg would be the holy grail for me, but it just isn't gonna happen with the way I drive and the state of my engine.

Brian Carlton · #6 12-24-2006, 11:57 PM

Damn, and I thought the SD was doing fantastic when it topped 31 mpg on one occasion. Normally, it manages 29's on the summer fuel.

I drive a bit faster than you do, however.........typically 65-70 for 95% highway traffic.

You've got a good running machine there.

These W126's are definitely sensitive to the wind. 60 mph gets you significantly better fuel economy than 70 mph.

Brian Carlton · #7 12-25-2006, 12:00 AM

Quote:

Originally Posted by ForcedInduction

It might also have something to do with you having almost 200K less miles on your engine (My engine has roughly 380K miles).

........that's 300K less miles, Lance.......

Ara T. · #8 12-25-2006, 12:18 AM

I always get 20 mpg, city driving. After a while I stopped caring. Engine runs good, car drives well. That's that for me

Knightrider966 · #9 12-25-2006, 12:26 AM

That's pretty close to my fuel economy! Mine got much better when i switched over to a K&N oil bath air filter!

DslBnz · #10 12-25-2006, 12:28 AM

Quote:

Originally Posted by Brian Carlton

Damn, and I thought the SD was doing fantastic when it topped 31 mpg on one occasion. Normally, it manages 29's on the summer fuel.

I drive a bit faster than you do, however.........typically 65-70 for 95% highway traffic.

You've got a good running machine there.

These W126's are definitely sensitive to the wind. 60 mph gets you significantly better fuel economy than 70 mph.

The W126's are fuel hogs at speeds 70 +, aren't they? I get only about 24 mpg if I sustain 85 - 90 mph driving all day.

A W124 with a 603 barely burns any, in my experience (about 31 mpg at 80 mph). The combination of the large frontal area, the extra weight, significantly poorer aerodynamics, and the 2.88 differential does not bode well for efficiency. But it is an S-Class,...What the heck.

#11 12-25-2006, 01:32 AM

Quote:

Originally Posted by Brian Carlton

........that's 300K less miles, Lance.......

Okay, I WISH it was almost 200k less.

tarbe · #12 12-25-2006, 08:14 AM

Wind resistance goes up by the square of the velocity increase. So as has been noted, speed kills.

So a 20% speed increase from 60 to 72 increases wind drag by 44%! Double your speed and quadruple the resistance, etc. And wind drag is your enemy on the highway when it comes to fuel economy. Weight is the big killer around town.

Brian Carlton · #13 12-25-2006, 09:06 AM

Quote:

Originally Posted by tarbe

So a 20% speed increase from 60 to 72 increases wind drag by 44%! Double your speed and quadruple the resistance, etc. And wind drag is your enemy on the highway when it comes to fuel economy. Weight is the big killer around town.

The worst part about this is the increase in horsepower............73% increase in horsepower necessary to overcome the wind when increasing speed from 60 to 72.

Brian Carlton · #14 12-25-2006, 09:08 AM

Quote:

Originally Posted by DslBnz

A W124 with a 603 barely burns any, in my experience (about 31 mpg at 80 mph). The combination of the large frontal area, the extra weight, significantly poorer aerodynamics, and the 2.88 differential does not bode well for efficiency. But it is an S-Class,...What the heck.

Yep, they're considerably better than the W126 with the same engine. I'll bet that top speed in a W124 is at least 10mph faster as well.

stephenson · #15 12-25-2006, 10:55 PM

Doesn't 31 plus seem a bit high? I have owned 123s and a 126 and have never even gotten close to that with either - 123 usually averaged around 25-26 with 60/40 highway and 126 with 3.5L gets around 23-24 with same mix ...

Is it really possible for there to be a large mass of us getting in the 20s and a very small number in the 30s? Not meaning to doubt anyone's mileage computations, but just seems out of the statistical norm ...