Mobilube HD Plus 75W gear oil

[northernT4R]

Hi - has anyone used Mobilube HD Plus MG75W gear oil in their manual transmission? I've just been to the local Toyota dealership, where they insist that they use this lubricant in all manual transmissions, diffs, and transfer cases. It has a GL-5 API rating.

The general consensus in these forums is to stay away from API GL-5 gear oil in the manual transmission, and use GL-4 instead. The Toyota techs assured me this lubricant is appropriate for use in manual transmissions.

Confused to say the least.

 

[Swimmerboy2112]

Hi - has anyone used Mobilube HD Plus MG75W gear oil in their manual transmission? I've just been to the local Toyota dealership, where they insist that they use this lubricant in all manual transmissions, diffs, and transfer cases. It has a GL-5 API rating.

The general consensus in these forums is to stay away from API GL-5 gear oil in the manual transmission, and use GL-4 instead. The Toyota techs assured me this lubricant is appropriate for use in manual transmissions.

Confused to say the least.

Former Toyota mechanic here!

DO NOT use GL-5 gear oil in the transmission, it is caustic to brass and will literally eat away your syncros. Pick up some GL-4 gear oil, I prefer Redline MT-90.

However, GL-5 is ok in the t-case and diffs.

 

[northernT4R]

Thanks for your reply!

It is very frustrating to think that the Toyota techs were not providing me with accurate information!

I'll look into finding some GL-4 fluid for the transmission, though it seems to be pretty scarce. I've not been able to find anywhere local (Toronto, Ontario) that sells Redline MT90 or the AMSoil equivalent. All I've been able to find is Valvoline MTF.

 

[pluton]

The Toyota owner's manual says GL4 or GL5 for the trans.
Interestingly, Nissan specifies GL4 only for their manual truck transmissions.

Does this Mobilube HD Plus MG75W oil have some more numbers after the '75W' part, like 75W-90?

 

[KidVermicious]

Thanks for your reply!

It is very frustrating to think that the Toyota techs were not providing me with accurate information!

I'll look into finding some GL-4 fluid for the transmission, though it seems to be pretty scarce. I've not been able to find anywhere local (Toronto, Ontario) that sells Redline MT90 or the AMSoil equivalent. All I've been able to find is Valvoline MTF.

Amazon. I get my MT90 on Amazon, it's a better price than any storefront and the shipping is free. Royal Purple also makes a synthetic GL4 that works well.

[MENTION=51788]Swimmerboy2112[/MENTION], can you or anybody confirm that the R series trans have brass synchros? I know the W series does, but I hadn't heard that about the R transmissions.

 

[Swimmerboy2112]

Amazon. I get my MT90 on Amazon, it's a better price than any storefront and the shipping is free. Royal Purple also makes a synthetic GL4 that works well.

[MENTION=51788]Swimmerboy2112[/MENTION], can you or anybody confirm that the R series trans have brass synchros? I know the W series does, but I hadn't heard that about the R transmissions.

Yes had one apart, can confirm the synchros are brass and the gear cones (which the synchros come in contact with) are polished steel.

 

[northernT4R]

The Toyota owner's manual says GL4 or GL5 for the trans.
Interestingly, Nissan specifies GL4 only for their manual truck transmissions.

Does this Mobilube HD Plus MG75W oil have some more numbers after the '75W' part, like 75W-90?

Unfortunately, no. Just says 75W. But when I compared the viscosity specs (cSt @ 100ºC) with the 80W-90 grade of the same oil, they both have the same value of 15.8. So figured they should have the same viscosity profile at elevated temperatures.