I start driving my wife's 89 300E to work recently. The car has 95000 miles with a K&N filter and some aftermarket muffler. I notice the gas mileage on the freeway is about 20-21 mpg. Comparing to my friend's 93 400E claiming 25-27 mpg on freeway. I also notice when I cruise at 70 mph on freeway, the engine rpm is around 3000 comparing to my other 6 cylinders cars like 300zx and Honda Odyssey are about at 2000 rpm, Does this sound right? Any advise would help.

This sounds about right. My '87 300E is about 3100rpm at 70, and gets about 20-22. Later E class, both 6 and 8s, used a different injection system instead of the one on our cars. BTW, my '88 Acura Legend coupe 5 spd is about 2800-3000 at 70 in 5th, and my '84 Toyota 5 spd is about 2900 in 5th. I am currently looking for a clean 1992-95 400E/E420 for the better fuel economy (sure!)

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John

2003 Firemist Red/grey leather SL 500
2015 Palladium Silver/black mbtex GLK 350
1987 Smoke Silver/burgundy mbtex 300E Sportline (SOLD)

Click to see 87 300E

You have to remember that the mid 1980's M-Benz cars were not made with gas mileage as the priority. Top speed and aceleration were more the norm back then. My 190e 2.3-16 only gets about 21 mpg on the highway and 17 around town. I am replacing the throttle position switch since I checked it out the other day and the small rubber boot around the switch was torn and the switch look corroded. Maybe this might improve the mpg's. My car has a minor idle problem, probably due to the car running in the limp home mode. Joe

Just did a few long trips in my '87 300E and got between 24 and 25 mpg on the highway........my speeds were 65-75 mph.
This car is new to me so it was a little better than I expected.

Brothers of The Benz
My 1987 W124030 with 174500 miles averaged 19.4mpg for calender year 1999. I've been to involved to tabulate year 2000.
Typically it returns 18-19mpg in city driving and 27-29mpg hiway at speeds 70-90mph.
I have made minor modifications to the exhaust, intake and ignition.
The engine is as original, never required any repairs.
I've never considered fuel consumption as number one priority but performance comes first. If it gives me good mileage and performance I'll take it.
Happy Trails Beep Beep from The Spiderman in Houston!!!