Quote:
Originally Posted by TFT4RL
I’ve been using the the platinum synthetic from Walmart. Never had an issue with it before.
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that's very good oil with a robust additive package, i strongly doubt that's where your problem is. Pennzoil had a PR disaster in the 80's with oil that was formulated wrong and sludged up badly...seems they're still living that episode down even today.
as Jivewalker said, overly extended change intervals for your uses along with poor PCV peformance and other minor factors like extended idling can contribute to oil varnishing in a way that might cause just enough sludge to affect a sensitive part like the oil control valves.