Now I come from the BMW world, where they had oil consumption down for a long time, from the late 70s to 2000, with the exception of pre 85 valve guide seals which didn't last much over 100K, they pretty didn't much use any oil. I had a 2000 528i that used no oil when I sold it at 253K. However in 2001, the 6 cylinder engines often started using oil. Sometimes a quart a thou or more. Seems they went to low tension piston rings for added economy, and in an attempt to keep scheduled maintenance costs down have very extended oil change intervals, up to 15K. Hence the low tension piston rings gum up, the return ports in the piston plug up and they use oil. NBD says BMW, it's within what we say is ok, and the original owners have usually sold it by then.
So, my question, suggestion, is, might it be a low tension ring problem and the oil ring not sealing as well? I've built engines with significant taper on the cylinder walls that used no oil, so I'm very skeptical of that argument, even though all the manuals make a big deal about taper, not overall bore. I cut consumption in my 02 BMW 525i from a quart every 1500 or so down to not having to add between changes with a particular brand/model of oil. Now time will tell, and I'm not sure of my hypothesis, so I'll not plug the oil for the time, but I did use it in the most recent change in the QX4. Now the problem is in my BMW it took 2 changes to take effect in reducing consumption dramatically, and I only put ~7K a year on the QX4 so it might take a while to make even a preliminary statement, other than I think...
Comments? Anyone agree? Or am I full of it?
