an oily puzzle
I've been enjoying the summer with my rebuilt 929 now 954 engine, but was a bit disappointed with the oil consumption. About half a litre per 1000km. Not enough for visible smoke, but enough to be annoying. All kinds of dark thoughts start arising, so in the end pulled the plugs and did a compression check, just to get a feel for the general state of the rings. All 4 cylinders gave 200psi, which is not bad for 12.5:1 pistons. I looked at the oil which has been in there since may, dropped a litre of it (diluted with gas) through a filter paper to see what debris was lurking. Not much, and not spectacular. A few last tiny specks of aluminium, presumably still hanging around since the break-in, no copper thank God, I even cut open the filter and flushed it out to look at what had been caught, and again, hardly anything.
So what gives? The pistons are from JE, are their oil control rings known for not being as good as Honda OE? Before the rebore the engine used virtually no oil. The spark plugs are clean and light tan colour, no oil in the threads. Oh, and I fitted new valve oil seals in the rebuild. I'd appreciate your thoughts.