ok so ive been on the penrite site and the hpr10w/50 seems to be the way to go, couldn't find a high zinc synthetic 20w/50!
 
what happened to electrical system?

20w50 mineral was recommended for the old 3.5 RV8.

The 4.0 and 4.6 is just a stroked and bored out 3.5 with fuel injection so i imagine mineral will be ok..

As long as it's changed frequently..
 
It's actually a bit more involved than that for instance the 3.5 had a stat in the normal place( in a bulbous thing) the p38 heart valve mixes hot and cold so potentially freezing cold water never goes on hot engine parts. The p38 still has the bulbous thing but it's empty. It runs at 100 degrees+. I had a cheap stat that meant it ran at 80+ it ran terrible. These will run on any old oil. The crank driven oil pump is somewhat better than the old v8. But they get filthy really horrible with Dino oil. I got mine from classic oils in Bicester. To me 10/40 is a bit better than 20/50. But 20/50 will make it run smoother but it's black death on a stick at 34 degrees in traffic with slightly dodgy rad.
 
It's actually a bit more involved than that for instance the 3.5 had a stat in the normal place( in a bulbous thing) the p38 heart valve mixes hot and cold so potentially freezing cold water never goes on hot engine parts. The p38 still has the bulbous thing but it's empty. It runs at 100 degrees+. I had a cheap stat that meant it ran at 80+ it ran terrible. These will run on any old oil. The crank driven oil pump is somewhat better than the old v8. But they get filthy really horrible with Dino oil. I got mine from classic oils in Bicester. To me 10/40 is a bit better than 20/50. But 20/50 will make it run smoother but it's black death on a stick at 34 degrees in traffic with slightly dodgy rad.
so the penrite hpr 10/50 should be ok then, seems to match what a few are saying, synthetic and high zinc?
 
Yes ticks all the boxes. All bar catalytic converter life. Zddp isn't so great with them but that's the reason normal oils are not using zddp.
 
I concur what has been said above a new cat is significantly cheaper than a new engine.. ;)
 

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