1997 c230 revving @ 3k rpm @ 75mph normal?

[Seattle_202]

Just bought a 1997 c230. My car is driven mostly on highways and at 75mph the engine is at 3k rpm. I think that this is very high and its affecting my gas mileage. I have a 3.0L V6 honda accord that gets 28+ mpg and this one is barely getting me 25mpg. Question is, is this normal and can i tune anything (timing, ecu, etc) to run the car at a lower rpm? Any suggestion is appreciated.

[zmatt]

rpm at a given speed has nothing to do with tuning and everything to do with gearing. 3k at 75 sounds about right. The gearing is set to do about 2k at 60mph which is common highway speeds. If you are speeding your mpg will be lower lol. Also your mpg should me more like 30mpg highway, that's about what I experience, but then again I drive the limit.

[Seattle_202]

thanks zmatt, but i have 2 other vehicles and at 75mph they're barely hitting 2500rpm. and also they're both still getting more than 28+ mpg doing that same speed. thanks anyways.

[MikeD]

...but you have a 90s Mercedes that weighs over a ton and a half. It's expected that your mileage won't be so swell compared to light japanese cars

[anf6789]

the early 202's with the 722.4 trans did not have overdrive, therefore the higher engine speeds, right in the powerband for autobahn crusing

[zmatt]

thanks zmatt, but i have 2 other vehicles and at 75mph they're barely hitting 2500rpm. and also they're both still getting more than 28+ mpg doing that same speed. thanks anyways.

You are assuming that the mercedes has the same gearing as the others. It doesn't. I plugged the numbers for our cars into a speed/rpm calculator and for our 16inch stock wheels, with 5th gear being .83 ratio and a 3.46 final drive you have 74.6 mph at 3000 rpm. So it is absolutely correct. Again gearing is set in stone, even if your motor was running poor for a given speed and gear its rpm would the same. The amount of power it is making at said rpm would be different though.

You have nothing to worry about. Our cars are just set up for German roads so the gearing is different on the top end. Makes hitting 130 cake though.