gear oil help please

[electrolover]

so before i became a bitoger i changed the rear diff fluid on my new to me pick up (04 f150) i went with super tech 85/140 and lucas. i think it may have been a bad idea because it recs syn 75/90 or 75/140 for towing. its a limited slip diff.
i have thought about going with mobil, synpower, or royal purple.
any thoughts on these products? which would you pick?

 

[qdeezie]

Well, I know you didn't list it in your choices but Super Tech does make a 75/140 full syn.

 

[Not the Autorx Frank]

Ford also has a friction modifier you add for the LS. You can get it at the dealer...

 

[electrolover]

i know it probably makes no difference but id rather stay with a trusted name. i usually get the friction mod from oriely's, i dont know what brand it is, but its right here and cheap.

the fluid change is going to take 2.5 qts and price is and issue. i would really like to get it done so i can quit worrying about it.
the valvoline and mobil are around 8 and the rp is 13. i dont do any towing but do i need the extra protection of a 75/140? it is a bit more expensive than 75/90

here are my choices from my local warehouse:
castrol syn 75/90 8.89
mobil 1 75/90 7.99
royal purple 75/90 13.99
valvoline 75/90 7.99
royal purple 75/140 13.99

 

[unDummy]

If you tow or haul a lot, stick with the 75w140.
If you don't work the truck ever, use the 75w90.

Brand is for you to decide. ANY will serve you well.

 

[Barkleymut]

I have the exact same truck and engine...I just changed mine out with Mobil 1. I think it was 75/140 and it already has the LS stuff in it. I didn't want to have to worry about it for 50K and thats why I went with syn.

 

[MetalSlug]

Originally Posted By: Barkleymut
I have the exact same truck and engine...I just changed mine out with Mobil 1. I think it was 75/140 and it already has the LS stuff in it. I didn't want to have to worry about it for 50K and thats why I went with syn.


If I was u, i do go to ford dealer and buy a bottle of addictive. event mobil 1 say it already have the additive, add it anyway.

 

[unixguru]

I've used Mobil1 75w-90 and have been very happy with it back in 2002-2005. Right now I would probably go with Amsoil 75w-90, just because pour point of M1 is only -39C (amsoil is like -50C). But going by price/performance it's hard to beat M1.

 

[AzFireGuy79]

I dont see what he is gaining with a 11C spread between Mobil and amsoil?? He doesnt live up at the north pole. Between those two I would just toss a coin. Both great gear oils. More than adequate for any winter in any of the 50 states.

 

[electrolover]

i do ALOT of highway miles so my main concern is foaming or air pockets in the oil.... if that makes any difference..

 

[djquik1]

All of the Ford spec has superseded to 75w140 now regardless if if came with 75w90.

Honestly, I have to do a dump on my 2010 this weekend of gear lube and trans fluid because I got the truck stuck and got it a little hotter than I am comfortable with so I am swapping them.

Going with the Royal Purple and Mercon LV