Okay lets start with a valid question. Is it okay to run 100 octane in our cars? I only wondering being that I use to put 100 octane in my old Honda and run it hard to try and help clean it out some. That's just something I was told would help. Not even sure if it did, but it sure was fun.

And for the unique question. What should one do if they miss and fill up a gas powered car with diesel? I saw a family once half fill their tank that way on a Chevy Malibu. I wanted to help them, but the only thing I could think of was to get the sucker towed.

 

I would be willing to put 100 octane in, but if I accidentally put diesel in I think I would purge the tank.

 

I run Sunoco 100 race gas in the car... Not sure it gains me anything, but it doesn't hurt the engine. All the plug tips are still showing signs of a very lean condition (white deposits).

When we were kids we filled an old rotary Mazda with diesel accidentally and trashed the engine within 5 miles... So I can safely say, don't drive the car at all, drain the tank and purge the fuel system. Otherwise you'll be looking at buying a new engine...

 

You can idle a gas engine on diesel but that's all you can do with it.

I believe diesel has a lower octane rating than gasoline. And it also burns easily when in vapor form so it will predetonate extremely quick, which is why they inject diesel into an engine instead of using wet vapor manifolds.
That also should explain why your rotary took a dump when you ran diesel through it. Those seals are fragile while easily destroyed by preignition.