Amsoil rear diff 75w-90

So I changed my rear diff oil with amsoil 75-90. The OEM fluid looked great light honey colored at 60k. What I did notice was the thickness, as compared to amsoil. The amsoil felt half as thick and poured very easy. The truck is running amazing after the swap. It feels very light . Best I can describe it is taking my foot off the throttle when driving down hill and truck just maintains the speed. Y’all think that the fact that the OE oil is 5 years old had something to do with thickness? Gas mileage has gone up too.

 

What's the viscosity grade of new oem fluid? Same?

 

OEM is 75w85 which is a rare fluid to find in store so most just use 75w90 since it's easier to find.

 

if that's the case, new oem/Toyota fluid should typically have a lower viscosity than the new amsoil that the op used.

I think whatever op "felt" had more to do with old/thick/used oil than the brand of oil ... Other than that, is Amsoil a better gear oil that oem? I would say most likely.

 

So it wasn't running well before the change?

What grade hill are you going down to be able to maintain speed with no gas? Engine braking alone would require a pretty steep gradient to do that, no matter how well your diff spins.

Placebo, JMO

 

Amsoil spends a great deal of money to convince people their lubricants are great. I know that with regard to their motor oil for diesel engines theirs provides a poorer additive mix than other motor oils costing a third as much. 75% of the diesel motor oils have a superior additive mix. For a rear differential with limited slip I would want the manufacturer's recommended lubricant though that is not a concern with the Tundra as it lacks a true LSD.

 

Placebo. Not gonna make a noticeable difference in feel, either way.

Is Amsoil better stuff than OEM? Yes. But not gonna get into it as you can see above, we’re already starting to make shit up. You did good.

 

This^^^

 

The 80/90 is not synthetic.