Originally Posted by sterg
I'm using motorcraft 1/2 synthetic 5-30. I don't think 7500 miles is too long before the oil has to be changed. It's not even that dirty at 7500.
I'll give you my professional opinion as a technician, a 15 year Ford tuning and engine building veteran, and as someone who has spent immense amounts of time on the subject of oil (thank the GT500 world for that).
First of all, Motorcraft oil is complete junk. This is not my opinion, this is fact based on compiled oil analysis data that has been databased over the years as compared to other oils. It has horrible shearing (it shears down to a lighter weight within 2000 miles), and very low burn off tolerance (it burns off very quickly). The additive package is usually completely depleated by 5000 miles. And this is for the Motorcraft full syn, so think how much worse the semi is.
Second, I do not believe it to be a good idea running oil past 5000 miles, unless you are using oil that can make it that far. The manufacturer intervals on maintanance things are getting rediculously stupid in the past few years. If you are running motorcraft oil to 7500 miles, then I am not surprised you are burning it off.
My PERSONAL advice, is to switch to Amsoil 5-20 full syn. It has the highest burn off rate of any brand, has a better additive package, does not shear down, and I run my engines at 10k intervals with it.
With that said, this is my opinion. I know how oil threads can go, and I am not trying to start a 30 page discussion on oil. I've been through many of them.