I have the C230 which is the same engine I think. It matters a lot how you drive. There are ways to get great mileage and there are ways to get lousy mileage. People routinely report getting 31 MPG with the C230. I can get almost 40 in the summer using various techniques such as pulse and glide and averaging around 62 MPH. But that is for pure highway driving. Usually you have a little city driving on each end. You should be able to get 30 unless you drive very fast.

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1998 C230 330,000 miles (currently dead of second failed EIS, yours will fail too, turning you into the dealer's personal human cash machine)
1988 F150 144,000 miles (leaks all the colors of the rainbow)
Previous stars: 1981 Brava 210,000 miles, 1978 128 150,000 miles, 1977 B200 Van 175,000 miles, 1972 Vega (great, if rusty, car), 1972 Celica, 1986.5 Supra