Motorcraft 75W-140 is synthetic. Also, RP makes a 75W-140. I just bought 3 quarts of it.

 

Ok i screwed up i refilled differential with royal purple 75-90 i will change it tomorrow back to RP75-140 but as fas as my motor oil i should be alright running 10-30. thanks

 

I say yes, but some people will disagree with me.

 

I say maybee

I would prefer you run 5W-30 but at least for the summer you should be OK. Personally I run 0W-20


You should be OK for a day or two with 75-90 gear oil, but would change it out fairlly soon

 

my neighbor who just left is running 10w40 RP in his 1999 4.6.

he was using mobil 1 but was going thru a quart per 1200 miles...running 5w30.

with the RP 40 wt oil, he said the motor has used about 1/2 quart and it's been around 2800 miles now. I guess that's much better. I did warn him about going to an oil that was too thick, could create oil starvation in critical areas.

I'm sure he won't change his mind, he's tickled pink with the RP.

 

I like Amsoil. It's in the tranny also. I believe it's longer lasting than the others, although they are bordering on pricing themselves out of the market IMO. Their d-a-m-n oil filters are approaching $15/each, and as others said, oil changed as often as it's supposed to (or more) is the major factor. Amsoil loves the 4-ball wear test (film strength) which shows a smaller scar than all the other synthetics in their tests. We run the crap out of our motors, so I kinda feel a little better thinking the oil in there is protecting it from wear as much as possible.

Tim, I appreciate your CR article. Very interesting.

In the end, most of our trucks suffer from Ford's ***-up called Modular Motors and junk internals, not oil type or even viscosity. Nationally recognized race engine builder Ronnie Crawford (local around here) has had these (not just from Lightnings) come in with things breaking that before now were unheard of in low performance applications. Valve heads splitting in half, defective blocks, terriible shake on brand new engines from lack of balance, oil pumps falling apart, and many more things that he said that I can't even remember. The general overall engineering of the motor is a disaster, so much so that Ford is still revising them as they go because of being such junk. Our trucks do well only because these motors have a HUGE stroke coupled with roots style instant boost which gets these heavy vehicles moving. The heads don't flow.

 

I'll add a "data" point. I've seen many test motors torn down after hundreds of hours (simulating ~100k miles). All the motors were run with "dino". Many of these motors had cylinder cross hatching that showed virtually no wear. Granted they were run in cleaner and more controlled environments than any fleet motor would be but they spend most of their time at very high loads and they come out quite clean.

 

THANKS DON
I just changed back to 75-140 weight just got off phone with JDM they recommend 5-20 weight in thier built motors. then 5-20 it is.

 

You mean a fully ported 2V head flowing 220cfm sucks??? I have to laugh when I see that...GM is releasing their L92 castings that are flowing 320cfm STOCK and they're about $550 each with valves and springs for a .650" cam. Ford's idea of performance is a little lacking...

 

Does royal purple, make supercharger oil. thanks

 

They make a 50W synthetic motor oil. Kenne Bell recommends a 50W synthetic in their superchargers. I use RP in my KB.

 

What weight do you run, to start with I really couldn't make up my mind between mobil 1 and royal purple so i choose royal purple. thanks

 

Knowing what i know now about motor oil i will never run 5w-20 oil again the automotive manufactures use this light weight oil to try to get better mileage
CAFE. My uncles f-150 was making a noise inside engine when they tore it down it had bearing wear with 120000 miles on it and camshaft wear he lives in a hot climate and he used 5-w20 He begin to lose oil pressure for about the last 5000 miles the motor was a 5.4 trition so i am glad i went with a 0-30
oil. check AMSOILS web site and see what ROBERT RILEY has to say about 5-20 oil he does not recommend it. If you would like info on this email me your email address.

 

With 120K miles on the engine I'd think the oil had little to do with it. Also, there is very little difference in using a 0W-30 oil over a 5W-20.