Hi. Since I bought my 89 Jimmy, it has used oil. I knew that when I bought it, but I didn't think it would go through as much as it does. Here are the symptoms: 208 000KM - 125 000Mi all stock About 3 seconds to start engine from cold Instantly starts when warm and puffs blue smoke on startup Compression is ~135-140 on all cylinders EXCEPT #8 is 120 #8 Sparkplug black and tarry Coolant is clean Vacuum Gauge reads ~18" but rapidly quivers between 17 and 18" Runs great when cold, no blue smoke at all - no pinging. Different story when at operating temperature... Cruising very light throttle for a while, then slightly increase throttle produces a two or three very quick knocks and a big blue puff out of the exhaust. Pedal to the metal when hot, blue smoke trailing vehicle. I think the engine is actually quite strong. I've got 3.42 open diff on stock tires and can chirp the tires from dead stop. I initially thought the problem was all in the valve guides and seals as indicated by the vacuum gauge, BUT from what I have read, worn guides and seals should not affect engine compression. I understand that oil being sucked into the engine can cause detonation from increased compression, and as the oil becomes less viscous at running temperature more oil can be sucked in... But does anybody think that there is more wrong here than just worn valve guides/seals?