YouTube: Fifth Gear

Can You Run Gasoline in a Diesel Car? Diesel in a Gasoline Car?

We'll start this post off by saying do NOT try this at home. Pumping a tank full of gasoline into your diesel-powered car (or vice versa) is a bad idea.

If you're curious what would happen, British TV show Fifth Gear tried it for you.

First, a very few basics about internal combustion engines. Gasoline engines use a spark to ignite their fuel. Diesel engines use very high pressure to induce ignition. Plus, diesel fuel works as a lubricant for the fuel pump, while gasoline will not.

So what happens when you try to run a gasoline engine on diesel? Watch the video for the whole story, but the short answer is: It's not good.

Fifth Gear host Jon Bentley poured five liters of diesel into a gasoline-powered Ford Escort. The car runs OK for a bit, but soon begins to lurch and jerk. Any permanent damage? Surprisingly no.The car even passes an emissions test.

But are things as rosy if you put gasoline in a diesel-powered car? As Bentley points out, experts would probably have you replace pretty much the entire fuel system if you made this gaffe. That ain't cheap. And, apparently, not always necessary.

Bentley ran a diesel Vauxhall Astra on five liters of gasoline for a good 15 miles. He even observes a bit of performance improvement. But, during the subsequent emissions test, the poor Astra throws in the towel.

Is the little hatchback dead? Surprisingly, after a refill of diesel, the car lurches back to life with seemingly no permanent damage.

But, as Bentley points out, that would probably not be the end result with a newer diesel engine. Higher fuel-pump pressures and closer tolerances would likely mean a newer diesel engine would not survive a tank of gasoline.

Again: Do NOT try this at home. But, if you do, send us a video.

This post was originally published on January 5, 2018.