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How heavy is too heavy? When we first bought our 2005 Expedition about a year-and-a-half ago with 104,000 miles on it, it ran fine until I switched all of the fluids over to Amsoil oil. Within a month, I happen to check the oil one day and it was 2 quarts low. I've heard some horror stories about running synthetic in a used engine so I switched back to Mobil 5000. The engine stopped using oil but within about another month, the engine developed the dreaded dieseling issue, which it has to this state yet. I changed out the VCT solenoids and switched over to 10W-30 but the engine still Knocks. Should I switch back to 5W-30 again?
If a cam follower fell off, you would have a blinking Service light. Running 2 qts low, may starve top end, if you rev it 4-5K. I own a Lincoln 4.6l 32V DOHC. It had a start up rattle, with Motorcraft full Synthetic 5W20 and FL820. I switched to Mobil 1 and a XG2 ultra syn filter and rattle went away. Amsoil is not API approved and does not have starburst seal on bottle. That is why, it is not sold in stores. Amsoil claims they do want to pay for API fees. Amsoil is very pricey and sold through "authorized" dealers(aka, people selling out there home). Some say its is all clever marketing. If it was a truly a great product, it would be on the shelf, next to every other brand.Amsoil OE is now API approved and sold in some stores. It will not void warranties.
