Synthetic gear lube for diff and standard trans? Is it worth it?

[zieg85]

I am going to change the gear lube in my 85 C-20's SM 465 and 14 bolt FF.  Anyone using synthetic gear lube?  Opinions, and gas mileage improving?? Is it worth the extra $??? 

[85MudMonster]

Are you talking about like royal Purple? Cause I've heard nothing but good stuff about that. I don't know if you watch the automotive shows on TV, but some of them have tested the car/truck before and sfter swapping all fluids to synthetic, and consistently gain about 10hp or so. Harley Davidson did a test of RP in their bikes and showed a 20° engine temp differance between standard oil and RP full synthetic. I myself have never used synthetic in an older vehicle. But synthetic is the only kind I run in my '04 Mazda.

[zieg85]

Hadn't seen the shows, only broadcast TV, can't see the need for cable TV.  Hadn't thought of RP, just had read a little on the Mobil 1 and Amsoil.  I don't run the truck but 2500 miles a year but a smidge better mpg would be nice and the extra $ spent would eventually pay for itself.  I use Castrol Syntec for the engine, just never did anything with the rear or trans.

[85MudMonster]

Well, I would try it, it won't hurt anything. And if synthetic really works the way it is designed to then it will give you better mpg's as it should reduce heat and stress on the internal parts. But, as far as Mobil1 over Royal Purple or Amsoil, or any other brand, I think they're all about the same really. The big concern is Conventional vs. Synthetic, and from what I have read and experianced synthetic is always better. I go about 7,000 miles between oil changes and the RP is a light purple when I put it in and after 7k miles it comes out the same color.

[werewolfx13]

I like Amsoil a LOT, its completely safe to run 20k miles on an oil change with amsoil, but if you use a really good quality wix (napa gold) filter, you should change the filter at about 10k miles, anything less (like a fram or STP), change the filter every 3k max. 

I'm not sure about in our trucks, but I know in the 3rd generation (89-94) Nissan Maxima, you CAN NOT use GL-5 gear lube in the manual trans, it will destroy it in a matter of a couple thousand miles, it actually breaks down the soft metal gears. Somone who's used gl-5 in their truck with success with high mileage might want to chime in, I wont trust it in mine til I know its safe.

[DirtyLittleSecret]

I swapped to ALL Amsoil synthetics (motor, tranny, diffs/t-case, brake fluids, power steering, greases, etc).  With the K20 I did notice smoother shifts (the Mrs even asked what I had done to the transmission...if she noticed it, its significant ).  The rear end smoothed out as well.

So many benefits for an anal person like myself.  I see it as a cheap insurance policy.

[VileZambonie]

I wouldn't waste my $ on it.

[Mr79C10]

I like the AMSOIL web page
https://www.amsoil.com/index.aspx

[zieg85]

I like the AMSOIL web page
https://www.amsoil.com/index.aspx

Thanks, there was an excellent study done, thanks for the link.