GL4

[Rawze]

I have never seen elevated copper based on adding a gear lube .. only lower levels.

If you have higher levels of copper than normal, it is almost always an indication of moisture, coolant, fuel, excess soot, or other contaminants getting into the engine somewhere.

It can also be simply that you are showing copper on your overhead cams (very common after 500+k miles) combined with lower then normal oil pressures in the top-end due to excess wear, soot buildup, or other factors like valves adjusted incorrectly.

Also, summer time vs winter can cause differences in wear metals, or if load (heavier weights to haul at certain times of year, etc.) application changes happen. Wear metals usually go up/change slightly as oil gets worked harder, etc.

If you are really unsure about what you are doing and its effects, and you want to play it as safe as possible --> Then stick to manufacturer guidelines and --- simply don't use 10% mix of gear oil in your engine!. I use it in my own engine, and several others on here do as well with high success, .. I can see the difference and clear benefits for my own engine, but it may not be for everyone. Applications and use of the equipment may vary greatly for one truck to another, and this may throw that balance off.

For example: I don't live in northern-Canada and don't have to worry about my oil getting too thick for the pump to handle,.. for someone else... that might not be the case. If I did then I would have been using a full synthetic to prevent it.