rear differential oil question
 

Hello Everyone. I have a 2007 ford f150 FX2 5.4 with 3.55 limited slip rear end. It has 68,000 miles and would like to change the rear differential oil. I have read and I know the oil it requires is 75w-140 plus the friction modifier. I would like to use mobile one. But was reading and the mobile one sites states that is already has friction modifiers. Is that ok to use on my truck? Has anyone used mobile one and didnt add the extra modifiers?
Also some other brands say they have friction modifiers as well. Any advice? Should I use mobile one and add extra friction modifier or just go with what it has already?

***** here is a description from mobile one****

Mobil 1 Synthetic Gear Lube 75W-140 LS contains special friction modifiers designed for limited slip-type differentials. In most applications, the addition of special LS (limited slip) additives is not required. For axles requiring the highest level of limited-slip performance, OEM specific LS additives can be added to this fluid.

I have used Royal Purple with the friction modifier already in it. No issues. I don't see why you would have issues with the Mobil 1 either.

+1 on the Royal Purple though -using it with no modifier and no issues. If what you use states modifier "already added" then don't add it.

Ok. Yeah I have seen royal purple and mobile one have friction modifier in it. I would like to change the oil this weekend. Do all brands like royal purple and mobile one have the same amount of friction modifier? I believe my truck calls for 7oz? Is that what those brands have?

it will not hurt to add another additive bottle along with your 2-3 quarts of M1. it doesnt hurt to use it in non-LS rears either as the additive helps keep the heat/wear down and just downright better for things that are metal-to-metal. go ahead if you want, but that oil itself should have plenty in it to meet specification.

we put this bg LS2 in every rear we service

BG Products, Inc.