depends on the fluid used, capacity..etc

 

Redlne Synthetic for your rear dif is definitely worth the few extra dollars for the peace of mind of having the "best" fluid in there. Can't hurt right?

 

Peace of mind against what? Wear? No because for 40 years Toyota rear axles and rear wheel bearings have had a reputation of being troublefree for over 500,000 miles using ordinary oil.

 

Suppose synthetic fluid can really give better gas mileage, oil companies would have data all over their commercial. Also Ford and GM would put synthetic in their SUVs to improve the CAFE number. They don't do so.

Even diet pill commercials can find people that swear "I lost 20 pounds in two weeks!" I have never seen a synthetic oil commercial that says "I got 0.1 mpg more by switching to Mobil One" or "I got 1 more HP by switching to Castrol Syntec."

It may be all psychological. Synthetic does not perform better than regular fluid unless you live in the Arctic circle. Instead of wasting money on synthetic, how about take your wife out for dinner or buy your kid a Tonka truck or Barbie doll?

 

Changing to synthetics can net you about 5 horspower on the dyno. Will you feel that? no Does it have less friction? it must