Originally posted by Andy W.:
The reason the PSI dropped is because the 5w-30 flows better. All you are going to do with the heavy oil is blow seals and gaskets. The higher PSI is because it's not flowing nearly as well. A PSI that high is similar to someone having a blockage. Sorry but you are just plain stupid for running such a thick oil and I'm sure your gas milage is hurting to prove it! Higher PSI is bad, but so is 0!

-Andy



Well, Andy can be a bit brutal but he's right. If the engine was meant to run 15W-50 (which is diesel engine type oil) then Ford would put that in your owner's manual. That oil is entirely too thick for the Duratec, at any ambient condition (Florida, Death Valley, whatever).

I've seen Big Jim post about Duratecs that have encountered problems directly related to lubrication on a steady diet of 10W-30 in California.

But hey, if you think it's the right thing to do, don't let me tell you otherwise. It's your car after all.