[ThirdOfFive]

Originally Posted by Altavia

Diesel and gasoline are different types of fuel, and an engine that operates with one type isn’t compatible with the other fuel. So, what happens when you put diesel in a gas engine? Just putting diesel fuel into a gasoline car is bad enough. Attempting to drive a vehicle with diesel in a gas engine will cause it to stall as soon as diesel reaches the intake system, potentially clogging the fuel lines and damaging the engine.

What Happens When You Put Diesel in a Gas Engine?

Diesel is thicker than gasoline, and the more viscous fuel can clog and damage a gas engine’s injection system and other components. If you catch yourself putting diesel in a gas car, here’s what to do (and not do):

Do not start the engine. It’s crucial to keep the diesel in the tank and not let it into the fuel lines and cause damage.
Do not panic. Mixing the two fuels is not, by itself, dangerous.
Immediately call a dealership or local repair shop. Arrange for an emergency tow to get your vehicle to the service center.
A mechanic will drain and rinse the gas tank to remove diesel and its residue. If you didn’t start the engine, that’s the only service necessary. However, additional work may be needed if you drove with diesel in the gas tank. If you ran the engine until it stalled, technicians will likely:

Flush the fuel line
Service the fuel injector system
Check the fuel pump for damage
Replace the fuel filter

What Happens if You Put Diesel in a Gas Car? - Kelley Blue Book

Personal experience says the above is questionable. Didn't hurt the '08 Kia a bit at about a 50-50 mix. Gas-burners won't run at all on 100% diesel but I'm here to tell ya that the only injury a 50-50 mix causes is to one's ego. Can't answer for any mix with more than about 50% diesel.