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Valvoline Full Synthetic 75w-90 Diff Oil

daniels740

Member
Joined
May 8, 2019
Location
South Florida
Went to get oil + oil filter from Walmart today when I decided my diff was also overdue for a gear oil change. I don't even know if it has ever been changed.

I picked up two 1QT 'flex-fill' pouches of Valvoline Full Synthetic 75w-90 Diff Oil.

I have no idea what diff I have, but I am fairly certain it's not an LSD, so I wanted to know if this stuff that contains "limited-slip additive" should be alright for my '89 740 Turbo with an auto. I figured it couldn't hurt to ask.

Thanks in advance!
 
Using an oil with a limited slip additive is unlikely to cause any issues with a non-existent limited slip :)
If you had a posi, then you would need to be particular about additives. The Volvo **** used to be a whale-extract that I'm pretty sure became illegal to harvest.
 
I've had problems with full Synthetic gear oil. Used it in the V8 Wagon, pinion failed, used it in the F Prod SCCA race car, we got a race and a half out of the diff, twice. Both suffered textbook fatigue failure. There was no wear on the gears, but the full syn does not give/ absorb shock protection when the gears mesh, BTW the gears that failed are on my shop wall in the "hall of shame".
 
I've had problems with full Synthetic gear oil. Used it in the V8 Wagon, pinion failed, used it in the F Prod SCCA race car, we got a race and a half out of the diff, twice. Both suffered textbook fatigue failure. There was no wear on the gears, but the full syn does not give/ absorb shock protection when the gears mesh, BTW the gears that failed are on my shop wall in the "hall of shame".

Theres a huge range in performance and types of synthetic gear oil. I wouldn't discount the entire type of oil based on a limited experience.

Which type of synthetic were you using?
 
Gear oil

Theres a huge range in performance and types of synthetic gear oil. I wouldn't discount the entire type of oil based on a limited experience.

Which type of synthetic were you using?

At the time it was Mobil gear oil, it was back in the late '90's. As we found out it does not absorb shock well, went back to regular gear oil, later to Red Line shock proof gear oil, never had a failure since. Like I said in the above post I have the gears that failed on my Wall of Shame.
 
At the time it was Mobil gear oil, it was back in the late '90's. As we found out it does not absorb shock well, went back to regular gear oil, later to Red Line shock proof gear oil, never had a failure since. Like I said in the above post I have the gears that failed on my Wall of Shame.

I'm thinking synthetic has gone a real long way since the late 90's. That being said, I see no reason to be the cause of my own issues. I guess I'll wait until more people chime in. I have no issue with returning what I bought and getting something else, if anyone has better suggestions.

Thanks.
 
Anything in that diff will be fine. Cheap GL4, or expensive synthetic. As long as it’s not breaking down from too much heat or moisture.... it’s going to do just fine for another 50-100k.
For what it’s worth, we use 140w gl4 gear oil in the 240 rally car and change it out every day of racing, because the fluid’s burnt dark dark amber.
 
At the time it was Mobil gear oil, it was back in the late '90's. As we found out it does not absorb shock well, went back to regular gear oil, later to Red Line shock proof gear oil, never had a failure since. Like I said in the above post I have the gears that failed on my Wall of Shame.

I don't doubt you had the experience you did.

Synthetics and fluids have come a long way since then.

The bottom line is if you have something that's reliable and works then seems like a no-brainer unless you are trying to increase performance but reducing friction... etc....
 
Using an oil with a limited slip additive is unlikely to cause any issues with a non-existent limited slip :)
If you had a posi, then you would need to be particular about additives. The Volvo **** used to be a whale-extract that I'm pretty sure became illegal to harvest.

Are you for real?
 
I have always considered the whale oil talk as myth, since I only started hearing it recently.
This is the only place I have seen it printed, never in an msds.
https://www.lubegard.com/technology/
It is highly suspect, since they claim there were 1/8 as many auto trans failures before whale oil was made illegal. They also say car engines lasted longer. Bull****. Oil is amazingly good now compared to even 5 years ago. If anything, the super-long interval oild have less high pressure protection due to the larger detergent packages and less zinc (depending on the classifications), but choose wisely and reap the benefits.
BTW, some "synthetics" (I'm looking at you, castrol) are highly refined petroleum.. The MSDS is your friend in this case.
 
Regardless it was done by independent lab. Anyways valvoline and Castrol did well. Which I can pick up at local parts store.
 
Regardless it was done by independent lab. Anyways valvoline and Castrol did well. Which I can pick up at local parts store.

One more thing is that the study was from September 2007. Undoubtedly, every synthetic oil on that list has been improved upon or somehow altered since then.

It would be really interesting if they replicated the study with modern oils, although I do not think it is in Amsoil's best interest, in case other brands have caught up to or even surpassed their oil. I think it'd be cool to see the improvement of the individual brands within these last 14 years though.
 
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