Super Guppy - it appears as though your links relate to automotive engines and oils, as opposed to piston aircraft engines. Aircraft engines are a little bit different from a car or truck. The color of engine oil is certainly an indicator of engine condition - if it turns black very soon after oil change blowby is likely very high. I'd be somewhat concerned about this engine - I had an engine with almost identical symptoms cause me to make a forced landing immediately after takeoff last year - thankfully no damage. Ironically, we had completed the annual inspection about 30 hours prior, and compressions were all better than 65/80. Oil pressure was low - it would get up to the bottom of the green when cold, but would hover around redline at idle. Technically it met the Type Certificate Data Sheet but barely (by the way, max oil consumption can be found in this document, available free at
FAA: Home) Turns out our failure was from broken rings in one cylinder, and a bearing was starting to spin in the case! I suspect it is likely a valve was starting to stick as well, but we weren't able to confirm it for sure. Fortunately in my case, we were able to tear down the engine before we permanently damaged the crankcase and crankshaft. Was it expensive for the owner - oh yes!, but cheaper than trashing the whole engine. Disclaimer - my advice is worth what you paid for it - get a good mechanic and do a thorough checkup on this engine! Good luck and happy flying! CFI, A&P, and other alphabet soup
