1991 300E Mileage
 

WOW. :D

It's been over two years since I last calculated mileage. It's just too much of a hassle when I only go through a tank a month around town. But today I took a 400 mile round trip to go get some new wheels for my 300E so I thought I would check MPG.

390 miles - 26.5MPG

That's all highway, lead foot 75-80mph cruising with some bursts to 85-90. Odometer counts correctly. Does this mean I can hit 28.5-29mpg at 65mph with the "no flooring" rule in effect? I think all the work I've done to the car has paid off!

i am about to take a road trip with the 104....usually get 24 on the highway.... 103 usually get about 23

That's my experience, the only M103 I ever got 25 on, was the 5 speed manual.

Jim

Twice in the past month I've taken 300-400 mile road trips in my 124. Once I got 25.74 mpg, the other time 24.97 mpg. M103 with A/T, no A/C running. Even though they were all freeway miles, some of it was quite hilly, not only flat land. Car has always been regularly maintained, but I just replaced the O2 sensor with about 70K miles on it. Early indication is that the new sensor has improved my mileage by about 3-4 mpg. The last 4,000 miles combined city/highway mileage is 20.51 mpg (mostly before replacing the O2). I'm satisfied.

Isn't yours the smaller 2.6L M103, not the 3.0L engine?

Jim

At 80MPH I am running at 3200rpms.

Would altitude have anything to do with the increased fuel economy?

The last long trip I took with my 91 300E 2.6 (about 1100 mi round trip) I calculated close to 27mpg on the hwy as well.
I thought that was fantastic for an early 90s mid size, and unbelievable for an 18 year old car with 185K (at the time).

220K+ now and still one of the best running cars I've owned.

John, mpg should decrease at higher elevations due to lower air density.

Hmm. Everything else being equal that means I should be able to easily hit 30MPG at sea level @ 65mph. I'm encroaching on diesel territory with my 3.0L. :D

in steady driving from jupiter fl to savannah ga... i got 404 miles .....at fillup the car took 15.25 gallons.

new wires and plugs 3 months ago....new o2 sensor about 5 months ago.

Very doubtful unfortunately....You'll never see 30MPG out of a M103 KE unless dropped off a very large cliff.

I know I could hit 28 to 28.5mpg at 65mph with no flooring, and that's at altitude.....

I literally drove the piss out of the car on the highway yesterday and got 26.5mpg. Maybe only 29 at sea level. ;) :D

I've gotten over 30mpg several times in my 300E, it is possible...don't let the heavy-footed tell you otherwise.

MPG calculations
 

I think that one tank or one trip MPG numbers can be very misleading. A simple way to get a better base for calculating MPG is to fill up - set trip meter to zero. Don't reset it until the tank has been filled at least 4 times, keeping track of gals at each fillup. Then you can simply divide the miles on the trip meter (adding 1,000 if it has rolled over) by number of gals,

Driving at altitude improves fuel economy because of the reduced air resistance (lower air density) acting against the body of the car at speed. The difference in pumping losses are negligible by comparison.
Given the same driving style you will see reduced FE at sea level.
Go EFI or go home ;)