Mixing gear lube ?

[jdw1222]

On the back of mercury high perf gear lube, and regular gear lube it states not to mix with other gear lubes. Is there any reason for this? It even states not to mix the high performance with the regular mercury gear lube

most gear lubes state they are compatible or dont say anything about mixing. Cant see any problem with mixing. Any thoughts, other than mercury just wanting you to always purchase their oil ? have a few half quarts of different brand gear lubes I would like to use up

 

[edhackett]

It has to do with the additive packages. In the case of the two Mercury lubes, one is a synthetic base and the other is a blend. The additive packages have been optimized for each base stock. Additives work best in certain combinations and ratios. If you mix, you may dilute an additive below its optimum level. Half of one additive and half of another don't often equal the same level of protection as 100% of either. You could end up with a mix with half the protection of either separately.

Mixing most generic mineral based oils is probably going to be OK. Mercury and other manufacturers, Subaru for example, admonish not to mix gear oils. They have no idea of what you may mix. It would be best to buy enough of each of the types for a change and use them up that way.

Ed