Mustangs a 289 v8 btw..... but the metalurgy in those old engines was not nearly as good as today.

 

I have always been told not to run synthetic in an old high millage engine. From what i have heard you will usually end up with lots of leaks because the synthetic will break down sludge particles that may be sealing up some leaking gaskets. Thats just what ive been told and it could be total BS for all i know.

 

http://www.bobistheoilguy.com/ If you Can't figure out what oil you want to use after looking at this website, then none of us can help you. This "Bob" guy praises Mobil 1 a lot. And there's a lot of talk about detergents and what makes certain types of oil better then others. Goodluck!

 

My Jeep had just over 120,000 miles when I got it. Switched it over to synthetic 5w30 right away, now a little over 135,000 miles and has not leaked any more than it did before. It also runs a lot quieter, no more diesel sound.

 

No Zinc/Phospherous in Motor Oil any more?!!! Wow. Um, Energy Conserving grades(0w-20, 5w-20, 5w-30 and 10w-30) have LOWERED levels of Zinc and Phospherous, due to Government Mandated Emissions laws(Helps Cat Converters last longer), but Zinc/Phospherous isnt Gone. I think all Oil recommendations should be directed straight to BobIsTheOilGuy.com

 

 

you could put oilve oil in the 4.0 and it would still rock

 

Synthetic everytime. If you need more info check out the links in my signature, they give anyone a lot of good info. To each their own opinion but synthetic is a superior product.

 

mobil 1 fully synthetic

 

X2 i run 10W-40 cause i like the purple My engine still has a way to go, ive only got 167K on it