Well, at this point, both of my Jeeps are mechanically sound as far as engine and sensors are concerned, and the 97 has a brand new reman and reprogrammed PCM. In the summer, when I got into the whole oil debate, I found through a few different oil changes that my 88 ran better with higher oil pressure, better compression, and less leakage on 15w40 diesel oil. (that was before the felpro VC gasket) I also like that the diesel oil endures high operating temps without burnoff (the 88 was a hot head until I overhauled the cooling system) and has extended drain intervals and lots of zddp. A few other guys swear by diesel oil too, and since it worked well for me, and I bought my 97 with almost the same amount of miles I went with it. Both my trucks run great, they just make a LOT of comotion over 2500 RPM, and they seem like they are being held back when it is cold out and the engine temp is below 200*... Once they are up to temp, they run perfect and love the go pedal!