Need some guidance, Jeepers. I have a 2013 Rubicon Unlimited. I'm about to change a bunch of my fluids for the first time. I'm overdue on my diffs. Who knows (for sure) whether or not I need the friction modifier additive? Most places I'm reading say I don't need it. Dealership says I do. I've already noticed my actual differential fluid is different from the '12 and '14 models (80W-90 instead of 75W-90) So, I'm looking for someone who knows '13 model Rubicon. So torn on what to do...will adding the friction modifier hurt anything if not needed? Thanks so much!

 

It's not required for the Rubicon since the diff is open. No LSD like the Sport and Sahara.

 

Rubicon lockers do not require any friction modifiers. As far as differential oil, 80W90 (conventional) and 75W90 (synthetic) are the same and either will work.

 

If you ever plan to tow, jeep recommends heavier weight and the use of synthetic in the rear. 90-140 I think.

 

Thanks, guys. I have an email in to my dealership asking why they would steer me the wrong way!

 

because dealers suck. So many examples of that. My personal experience: they told me oil had to be changed every 3000 miles or I would void my warranty. Told me synthetic motor oil would void my warranty. When I brought it in to get my slow clock fixed, they told me they did a courtesy check of my drive line fluids and they were all dirty and needed to be replaced. Little did they know, I changed every fluid only a week prior. Lying bastards. Oh yeah, when I went there to buy an oil filter for my 2012 JKU the service manager asked me which engine it had in it. Really? Don't believe them. They are scum.

 

Two possibilities: They don't know any better; they want to sell you an unnecessary product for their own profit.

 

You don't need it as was stated. However, if you use synthetic, either 75w90 or 75w140, it will most likely have the additive in it which is not a problem. I use syn. 75w140 in the rear dif. and 75w90 in the front of my Rubicon. It's not an issue having the additive.

 

Almost all of the dif oils come with it these days. And as kik says, it won't hurt anything if you don't need it and have it (the other way around not so much). So I would just pick the oil you like, and put it in there.

 

Thanks again for all the help! It's just sad that the supposed experts on the legendary machine just, well, aren't! Glad we have a strong community of true jeep lovers.