If you got a very thick oil, yeah a mix of diesel and oil is good so it would lose on viscosity and would be easier to get it on and into the wood. But today’s engine oils are not really that thick and can be used without any mixing with oil of lesser viscosity such as diesel. Nowadays you can find those very thick oils mostly in tanks (military vehicles) and big machines not your everyday family car.
I mentioned that in particular because the house I’m living has beams that were treated with that mix when it was built, back in the 40’s. And the neither rots nor gets infested. But the added fire damage is there.
If you got a very thick oil, yeah a mix of diesel and oil is good so it would lose on viscosity and would be easier to get it on and into the wood. But today’s engine oils are not really that thick and can be used without any mixing with oil of lesser viscosity such as diesel. Nowadays you can find those very thick oils mostly in tanks (military vehicles) and big machines not your everyday family car.
I mentioned that in particular because the house I’m living has beams that were treated with that mix when it was built, back in the 40’s. And the neither rots nor gets infested. But the added fire damage is there.