I want to switch to synthetic, but the guys at the dealership it didn't matter, and a guy at the autoparts store said that it could cause problems (fuel pump to go out? I can't remember what it was now because I asked a few months ago) I have 140,000 miles do these guys know what they are talking about or is it just crap? I Had to edit this in sorry I forgot. I live in Indiana summer around 80 degrees winter around 32 and dealer uses 20w50 oil |