highway trip milage - PeachParts Mercedes-Benz Forum

Grdenko · #1 03-09-2004, 01:09 PM

i finally got to take a real highway trip in my car recently. i was really surprised by how great the milage was.

28mpg @ 80mph (cc set)
26mpg @ 93mph (average)

normally i get about 22-25mpg in the city, and i dont know what the milage is at 70 on the highway (i never go that slow), but i imagine its somewhere between 30-32mpg.

just wanted to know how im doin' compared to what you guys get.

#2 03-09-2004, 03:23 PM

I have no clue as to my milage since I don't have a working odometer. But, I would take a wild stab that I get 19-23mpg since I have a pretty heavy foot.

toknow · #3 03-09-2004, 06:06 PM

this car should get 33mpg at average 75 mph...it depends on the load of the car and other aspects

lietuviai · #4 03-09-2004, 08:38 PM

Quote:

Originally posted by Grdenko
i finally got to take a real highway trip in my car recently. i was really surprised by how great the milage was.

28mpg @ 80mph (cc set)
26mpg @ 93mph (average)

normally i get about 22-25mpg in the city, and i dont know what the milage is at 70 on the highway (i never go that slow), but i imagine its somewhere between 30-32mpg.

just wanted to know how im doin' compared to what you guys get.

Wow a working cruise control!

I'm lucky if I get 23 MPG's on the open hwy with my 300D. My fuel economy really suffers if I push it over 65 mph. The engine really sounds wound up when its at 75 mph. It kind of sounds like a lawn mower at that speed.

#5 03-09-2004, 10:10 PM

I have gotten as high as 28mpg on trips in the 300CD before, but that is at 60mph, when I get over 70mph, it goes down closer to the 24-25mpg range (Still slightly higher than the Subaru).

toknow · #6 03-10-2004, 10:29 AM

check your transmission, may be you drive on the third, what is the rpm reading at 65 mph & 75 mph. Also, there is a device called ALDA that needs to be adjusted to lower the enrichment of fuel. It is very important to do that as rich fuel may shorten the life of the engine.

lrg · #7 03-10-2004, 12:19 PM

The late California cars lose about 2-4 mpg vs. the Federal cars. My '85 wagon (which I believe is heavier than the sedan) gets about 23 mpg highway at a steady 75 mph. The 123 is also far less aerodynamic than the later cars so the efficency drops off rapidly as you increase speed. My city consumption is high but probably not relevant since I am constantly dragging the car up and down steep hills here (my brakes don't last too long either). A lead foot + steep hills = lousy mpg.

#8 03-10-2004, 12:45 PM

I know this is a silly question that is probably answered in the search, but....

What is your method for calculating mpg? I think my mileage is bad right now, but I'm not sure of the method. If someone would share exactly how they do it, that would be great!

dmorrison · #9 03-10-2004, 01:01 PM

Fill your tank up. Rreset you trip odometer, or note the milage if the trip odometer is broken. Drive the car, Just keep driving, just keep driving

Then fill the tank up again. How many gallons did you use.
Then divide the miles driven by the gallons and you have miles per gallon.

Miles/Gallon

If you have a W123 it will be in the 20's or so. If you tell fishing stories it will be in the 30's. If your in the 10's, you need to look at the car

Dave

lrg · #10 03-10-2004, 01:08 PM

Ideal method:
Determine accuracy of odometer using GPS or other accurate measure. Fill tank to very top and zero odometer. Drive as far as possible on the tank and refill to the top, noting the total gallons added. Divide the number on the trip odometer by the number of gallons you just added to the tank then multiply by correction factor. This gives you an accurate MPG. This is best done repeatedly and then average the results to smooth out variables like temperature, hilly routes driven, use of A/C etc.

Usual method:
Reset trip odometer or note mileage at start. Fill tank to top and drive. Refill tank noting gallons of fuel added and mileage driven. Divide miles driven by fuel added gives you a pretty good idea of mpg.

CSchmidt · #11 03-10-2004, 09:34 PM

Folks,

This may not work for a single trip, since most of our cars get good range per tank... but. If you do as said above, but over many tanks, you reduce the "fill-up" error to 1 time in many gallons. For example, you fill the tank, check the odometer and start driving. When you fill it, unless you are very careful to get it to the top with no foam, you might be more or less full by some amount ( a gallon or so?). 1 gallon in 20 is 5%.

So fill your tank, drive, fill, drive, fill, drive,.... and when you get a good fill again then check the mileage over a longer time period. This way the 1 gallon fill error may be over 100 gallons, or a 1% error.

Chuck

dabenz · #12 03-10-2004, 10:17 PM

1) Every engine has its own sweet spot. Two engines coming off the manufacturing line back to back will have different sweet spots. And it drives the statisticians (sic) nuts.
2) Every driver is different, and perceives the sweet spot differently. daBenz's original owner always said the sweet spot was 52mph. He drove truck for over 40 years, so I didn't question him. The second year I owned daBenz I drove 60mph and used less oil. His long term fuel mileage average was 34mpg, mine is 36mpg and still using less oil. In my opinion 60mph is the sweet spot for daBenz.