YES
Most readily available bio-diesels are about 90% diesel and 10% vegetable oil. So no, wont hurt.
Yes.
Diesel will not burn in a gas engine, flash point to low; it may clog things up but nothing permanent
It shouldn't, but remember diesel oil is much thicker than regular oil and it will take longer to get into the rest of the engine. I used it once on a ford 302 for several months and it didn't hurt but the rear seal was shot out and leaked like a sive. I don't know what it will do to another make of engine.
how much tranny fluid are we talkin and why would you want to? the only time i would do this is if you have a old mechanical diesel engine then a little wont hurt
run what is recommended. but higher sulfur will not hurt it at all current diesel fuel is 50ppm
No it is fine to switch back to regular oil.
The Navistar 6.0 is junk to begin with, so I wouldn't be too worried about that. As for off-road fuel, it won't hurt the engine, per se, as the 6.0 was manufactured prior to EPA2010 regs, but it is illegal to use red dye diesel in on-highway applications.
Mixing synthetic oil with regular (conventional) oil generally won't harm an engine, as both types are compatible. However, it can dilute the benefits of synthetic oil, such as improved lubrication and performance. Over time, this mixture may lead to reduced engine protection and efficiency. It's best to stick with one type of oil for optimal performance and protection.
A small amount of rubbing alcohol mixed with gas should not hurt your cars engine. The alcohol will burn with no problems.
Drain the whole thing ... the two fluids mix well. (but a few percent diesel will not hurt a gas engine.)
NO