2cokeman

The book and the filler cap say 5W50 only, but I am seeing in other forums people are using 15W50 and 5W20..........Any opinions??

zporta

this topic has been on here and on other forums a good bit...i was having the same concerns....i knew that i would stick with the 5w-50 but which 2 use. There is the Castrol and the Motorcraft...I was going to order the motorcraft online but i figured i would stop by the dealer first...i told them i needed oil for my GT500 and they brought me out the Castrol and they say they put that in all the Ford GT's and GT500 that come in for service...Its the cheaper oil in cost so and carried at many part stores so thats what i went with...about 6$ a quart

olddog

Here's the response from Royal Purple on the same question:

We recommend either our XPR 10W40 or the XPR 20W50.[/align][/align]A 5W50 is not a favorable oil to run in an engine due to the amount of polymers that must be added to make the 5 Wt perform like a 50Wt at operating temperature (polymers like STP - which are not desirable).[/align][/align]Also - using the API SM rated oils have a reduced amount of antiwear additives which again - is not desirable for this performance engine.[/align][/align]Thanks for considering RP.[/align][/align]David[/align][/align][align=left][align=left]Royal Purple Inc[/align][align=left]David Canitz[/align]1 Royal Purple Lane[/align]Porter, TX 77365[/align]281.354.8600[/align]281.354.7600 fax[/align]713.725,7207 cell[/align]dcanitz@royalpurple.com[/align][/align]

2cokeman

Then why would Ford specs tell us to use 5W50 if it is not the right oil to use???

StangPride02

Try contacting Dave Mann at the link below. I think that you will find him very helpful. He was a lubrication engineer at Ford for 22 years.

Dave Mann
Lubrication Specialist - Truck/Automotive Engineer
Society of Automotive Engineers Professional Member
Performance Oil Technology, L.L.C.
www.performanceoiltechnology.com
1-888-879-1362