pookster

What happens if API GL-5 gear oil is used in an API GL-4 gear oil application... ?

API GL-4 and API GL-5 products typically use the same extreme pressure (EP) additive system, with the API GL-5 having
about twice the concentration of a API GL-4. In service, these additives become active under extreme load and temperature
when the protective oil film can be squeezed away. EP additives work by forming wear-resistant compounds with the metal of
the gear tooth surface. As the gears mesh, these compounds shield the gear teeth from direct metal-to-metal contact that would
cause wear and damage to the gears. If too little of the active additive is present, proper protection would be compromised.
Too much of this additive could cause excessive chemical corrosion of the gear surface. If an API GL-5 gear oil is used in a
application where API GL-4 gear oil is called for, chemical corrosion of "yellow metal" components may occur, such as bronze
synchronizers, brass bushings, etc. This may lead to shifting difficulties or shortened equipment life.

Thx to 96 VQ 30 for the recommendation to not substitue GL-5 for GL-4. According to the info I found above from a Pennzoil site, it could "lead to shifting difficulties or shortened equipment life" - the two things I was trying to avoid in the 1st place!!

Guest

You're welcome! I made the mistake of putting the same Mobil 1 GL5 oil in my Nissan truck many years ago (didn't know better) and that led to undesirable results, so I ended up throwing away 5-6 expensive quarts of oil.