I just filled up my 97 PSD this mornin and it was getting 19.4mpg with a mix of some highway and around town driving. It's crazy high geared since its got 3.55 gears and is pullin 35inch tires. The only mods are 3" downpipe, 3.5" straight pipe and DIY intake. The worst mileage i've ever gotten was in the 16's and the best was 23 cruisin down the highway around 75 with a slight tailwind three weeks ago.