Well, here's one thing I've noticed, and it DOES have to do with oil.

It is my impression that if you have one of the many 103s that burn oil because of the valve seals, you end up with some deposits in the combustion chamber that raises the compression. The car will begin to ping under load after a while, even with premium 93.

The only way to rectify the situation is to floor it and blow all the crap out of the engine. I usually wait until some jerk is behind me who won't dim his headlights, or a tail-gater. After a few hundred miles of build-up, this will put out quite a cloud of smoke but it does cure the pinging.

And remember, the 102/103s don't have knock sensors.

That's my impression. YMMV.

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2012 E350
2006 Callaway SC560