Modern emission controlled cars are pretty consistent on actual mileage, but there is a lot of scatter in owner measured data. In order to have accurate readings one needs to record gallons and mileage at each fillup and look at the average of lots of data.

Also, odometer error has a big effect, such as when the car has shorter than OE tires. I have measured odometer error data on my car, and it reads 2 percent high with the installed tires, so my corrected data is two percent lower than the observed data.

The EPA numbers on my car were 18/26 and over the long run the actual averages are pretty close to this. In heavy urban driving mileage is in the high teens, low twenties in a mix of urban and freeway, and mid to high twenties on highway trips. I've recorded a couple of legs over the years at a little over 30, but they were slow. Mileage definitely drops off with higher average speed.

Since my car is a five speed with a 20 percent overdrive relative to an automatic and has no torque converter loss, the highway mileage rating is 1-2 MPG higher than an automatic as I recall. An automatic W124 with a 2.6 or 3.0 liter engine will probably be one to two MPG lower than my car in town and about the same as a 190E 2.6 automatic on the highway. The W124 has a slightly lower drag coefficient, but is offset by slightly higher frontal area.

I looked around for the EPA mileage data on other '88 models, but, sorry, I don't have it. It might be on the EPA web site.

Duke