The Mystery of the Disappearing Oil on Scooby Doo the Subaru

I had a Geo Metro engine once that DRANK oil. I mean a quart every 100 miles or less was pretty much the norm. I drove it really hard once and went through a quart and then some in about 5 miles… and had all the traffic behind me pulling over due to the smokescreen.

The engine ran great but had an air filter housing that had been busted and the previous owner never fixed it. The entire intake area was just filled with sand, grit, and dirt. You could scoop it out by hand. I actually removed the intake manifold and washed it out but the damage was done of course.

I was told by a mechanic that engines that burn oil this bad can actually run pretty well because so much oil is on the cylinder walls and this keeps the compression up like in a wet compression test.

I found a replacement engine and once I had it on hand, I showed that old engine no mercy. I revved it up to the rev limiter and smoke would just pour out the back. I would floor it off the line and just it up to the rev limited before shifting.

Somehow besides the oil burning, this thing ran great and was still getting 52mpg when I swapped the engine. I never figured it would be possible for an engine in this poor of a condition to run this well but apparently it is. I simply unbolted all the mounts and just lifted that little 3 cylinder out by hand. I repeated the process in reverse order and had it back together in no time with a new engine that didn’t just drink oil…

I suggest the oil control ring not only because of many past experiences with frozen rings but also because of a good example I went through.

I rebuilt a Subaru engine. It was done right; bored block, new pistons, reground crank, etc, etc. Once started it smoked a bit and I figured it was oil from the prior engine burning out. I drove the car home that night as a test.
It burned 4 quarts of oil in a 50 miles round trip and I was mortified at the thought of a huge come back.

Next day at the shop I ran a compression test 3 times with different gauges. A 185 PSI on all 4 cylinders.
So out it came and it was doing this on 1 cylinder only. With the piston out I could find absolutely nothing wrong with anything. The machine shop had bored and honed the cylinders and it appeared fine when put together. I let it go until the next day before making a decision.

I re-honed the one cylinder. Once back together with the existing rings and it was perfectly fine. That always baffled me because the cross-hatch the machine shop did looked fine and the same on all cylinders.

I wonder if running the balls off this thing would have seated that ring or if thing would have drank oil until it locked up due to having no oil. that is interesting but I have heard stranger stories. If the rings had seated it might have just been a slight oil burner. Either way, it sounds like what you did fixed it.

I know Subarus are picky about the ring gaps. I wonder if they were all lines up at the bottom of that cylinder and the oil just passed right through due to their horizontal design.