Why I add 12% (one gallon) of gear lube at every oil change...

[RStewart]

This is great info. I also read the thread about the oil bypass. I was interested in the bypass & extended drain intervals. After reading these two threads I've decided to go ahead with the bypass but keep my regular interval. I have a 2011 Freightliner Cascadia with a DD15 in it. Manufacturers recommends 10w30 oil changed every 50k miles. I've been running 10w30 Delo 400 synthetic blend & I change it every 30k miles. I also thought oil sampling was a great tool but now I'm thinking just sampling for info but changing the oil every 15k-20k miles.

I'm really interested in what weight of oil you use & what gear oil you add. This really makes sense to me.