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I am still trying to pick apart every little aspect on why our car slowed down! 2 years ago we ran brad penn 20w 50 oil which is partial synthetic and a napa gold filter. Last time out we ran 15w 40 rotella t oil with a cheapy fram filter. Between the 2 oils there wasn't a dramatic oil pressure change but there was a little. My question is has anyone tested the 2 oils and seen any et difference?



what did it run 2 yrs ago? What does it run now? What rpms, how are the springs?