BEST oil for engine and rear diff.

[CanadianDiesel]

Alright so I bought a Motorcraft Oil filter, and was wondering...what's the best oil for the engine?

I'll also be putting my 08 diff cover on. That being said what should I refill the diff with that may improve performance, even if it's extremely minimal?


Thanks in advance guys

[ZachBoyer]

I use the industrial whatever is the cheapest 15-40.... Im at 235k and runnin strong. Usually rotella, delo, etc.


Usually I just grab it from the shop whatever it is we use in Telehandlers. I know its 15-40

[choupique108]

im thinking hard about amsoil but i have used rotella for years.

as far as the rearend, synthetic is better just be sure you add the friction modifier

[CanadianDiesel]

Manual says 5-40... what's up with that? I thought those were for colder temps? So for summer use, 15W40 and then for winter go with 5W40.

So for the diff go with synthetic gear oil plus a friction modifier. Got it, thanks guys

[zpd307]

Originally Posted by CanadianDiesel

Manual says 5-40... what's up with that? I thought those were for colder temps? So for summer use, 15W40 and then for winter go with 5W40.

So for the diff go with synthetic gear oil plus a friction modifier. Got it, thanks guys

do you have posi? i think syn 75-140 is required for the sterling axle.

[countryraised]

Originally Posted by CanadianDiesel

Manual says 5-40... what's up with that? I thought those were for colder temps? So for summer use, 15W40 and then for winter go with 5W40.

So for the diff go with synthetic gear oil plus a friction modifier. Got it, thanks guys

You should not switch between synthetic and dino oils, so if you switch to 5w40 (syn) you should not go back to 15w40 (dino)

[Austinj427]

Originally Posted by choupique108

im thinking hard about amsoil but i have used rotella for years.

as far as the rearend, synthetic is better just be sure you add the friction modifier

Explain please.

[LOOSEWHEEL]

75W140 synthetic for the rear. Use Royal Purple and you won't need to add any friction modifier. Done.

[PolarBear]

The friction modifier is for the limited slip rear diff. Ford sells it in a small bottle, like 4 oz. I've read that some oils already have this additive in the oil and its not needed additionally but I still ended up adding half a bottle to my LS when I put Royal Purple in. Limited slip still works as good as it ever did and have not had any problems with "limited grip".

[zpd307]

limited slips are good...... if they are put together right. i had the factory posi rebuilt before i put it in my 03 back in the day. shim friction shim, plus there is room to add more shims and frictions. it was tight! most from the factory are shim shim friction or vice a versa, this is to make them not so aggressive.