What Happens When You Mix Diesel with Gasoline?

Some old timers might suggest adding “a splash” of diesel to the tank of your gas-burning engine for one of several reasons. More than likely, they’re recommending you do so to lubricate your fuel system and engine, or perhaps they’ll tell you it’s to smoke out the mosquitoes in your yard. Either way, it makes for an interesting result, as you can see in the video below.

What you’re seeing is Tom Gorak’s Dodge M37 billowing white diesel smoke after Gorak added a little (too much) diesel to the tank. While the smoking will more than likely clear up on it’s own once all of the diesel has been run through the engine, there is a chance that adding diesel fuel to your gas can cause damage to your fuel system, as diesel is formulated quite differently from gasoline and has quite a bit of lubricant, whereas gasoline does not.

The same old timer that told you to try this is liable to tell you he had a car back in the 60’s that had so much compression that it could run off either diesel or gas, but we’re willing to bet that’s an outright lie, as that was a common boast back in that era to illustrate just how “hot” an engine was, though it seems nearly impossible that any engine could switch between the two formulations.

Regardless of what you’re told, we can find no manufacturer of any gasoline engine that recommends you use diesel to lubricate anything in the fuel system or the engine itself, nor can we find any reference from diesel manufacturers recommending that you add gas to “burn out the carbon deposits”. If there’s anything to take away from his whole deal, it may very well be not to trust old timers you don’t already know really well.

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