Is it safe to use a high-quality 15W-50 synthetic oil (Mobil 1) in both the transmission and engine?

 

Engine is Ok but for the trans get the Mobil1 75w90 gear oil. The 15w50 will shear very quickly in a trans.

 

Not trying to disagree AND I also would use trans. Oil in the tranny, albiet a heavier one like Redline HD Shockproof BUT 75 wt. gear oil is only a 10wt. translated into motor oil specs and IF you are using the Mobile one 15/50 in lieu of Syn III, I think it IS A BETTER CHOICE. Just not as good as a purpose blended gear oil.

Some, however, say motor oil with the right specs is fine in the transmission. Lots of ancedotal material to support both ideas but makes no sense to me to compromise if a specifically made product is available and price competitive.

EZ

 

Just for additional "motor oil vs gear lube" viscosity info;

 

I use shell rotella t in both clutch and gears,we used them on large detroit diesels on tug boats and they ran samples reg to keep eye on how they worked,so if it is good for $150,000 up motors and it is cheaper than the mobile 1 15-50 I use in crank case

 

Those Detroit Diesels...do they get up to 300*F operating temperature like a TC96 will in the Summer? HDEO's will work but I like a 50w oil in the heat.

 

The additive packages in gear oil are very different from motor oil. Gear oils are usually more shear stable.

 

 

I run Mobil1 V-twin 20-50 in my engine and trans.

 

I don't see the point in trying to use one oil for two different jobs. I'd put gear oil in a tranny unless is is spec'ed for a different fluid.