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Would diesel fuel ruin a gas engine?

I work as an auto adjuster for an insurance company. Recently, I went on two claims where thieves are now drilling a hole in truck fuel tanks and draining the fuel out of the tank. The last one they drained the fuel out of a diesel truck though. This truck looked like a gas engine. I’m hoping for some just Karma and would the diesel fuel ruin their gas engine?

The gas engine will not run long once the diesel fuel gets from the gas tank up to the motor. Once the motor dies, it won’t restart. To get it running again will involve draining all the diesel fuel from the tank, purging the fuel lines to get gas back up to the motor, and perhaps pulling and cleaning the fouled spark plugs.

As for permanent damage, I think the gas motor can be put back in service but it is a messy job. There can be damage to the fuel injectors and other parts of the fuel delivery system. So, it the motor won’t restart once you have good gas getting into the fuel lines and the fuel injectors then you need to figure out what part(s) of the fuel delivery system are compromised and replace them.

The diesel fuel won’t hurt the block, pistons, cylinder walls, valves, and bearings so the basic critical parts of the motor are still sound. Once you have the motor running again, it should get an oil change with a new filter before going back into service.

If the mixture ratio is high enough (1 gallon gas to 10 diesel), a gasoline engine will not run for long on the mix i.e. only until the gasoline in the fuel lines is used up. If the mixture is low enough (maybe 1 gallon gas to 1 gallon diesel), the engine may start and run poorly. But, severe detonation is a possiblity under load. If the detonation is severe enough holes can be burned in pistons; pistons can sieze to the cylinder walls; rings can be locked; spark plug electrodes melt; valves burn; etc. I would guess that a gasoline engine could survive 1 gallon of diesel mixes with 15 gallons of gasoline but I would only do the experiment with an engine I was willing to sacrifice.

BTW the smell between diesel and gasoline is very distinctive and dissimilar so unless these thieves were really stoned insensitive, they would know they had diesel on thier hands.

Ruin the engine?? No… Depending on the percentage, the gas engine will run worse and worse and will refuse to start when cold…

The Achilles heel in all these new plastic tanks is the ease of puncture.
Dealership lots get hit en-masse at times and cost thousands.
The karma there is dealers don’t keep much gas in cars on the lot so the resulting take is not much gas at all.

I don’t believe that diesel fuel will ruin a gasoline engine.
When I was a kid, I had access to free kerosene. Kerosene is the same thing as Diesel #1 and is commonly mixed with #2 to prevent jelling in the winter. I mixed about half gasoline and half kerosene for use in my lawnmower. The mower engine ran the same as with straight gasoline as far as I could tell, started just as fast when cool and had the same power.

Way back, some old fashioned tractor engines used gasoline for starting and then were switched to kerosene while running.

With fuel system components now resistant to ethanol as well as gasoline and the additives that are used in gasoline plus the anticipated cure all “Mouse Milk” additives that people put into their fuel tanks, that would increase the chances of diesel fuel not being a problem.

With knock sensors to retard ignition timing, it is possible that detonation may not be a problem.

Both of these engines have pretty low compression ratios so they might tolerate very low octane rated mixture. Did you remove the head of the lawn mower engine subsequent to your use of the mixture and visualize the combustion chamber? Did this lawn mower engine have a steel block, piston, and head? Just collecting information.

A while ago, I read a aviation accident report where a twin engine plane came to grief after both engines quit. The airplace, a Chieftan IIRC, was misfueled with Jet-A because the side of the cowling was emblazoned with ‘TURBO’. On takeoff the twin struggled to pattern altitude before the effects of detonation caused the engines to seize. On tear down, holes were found melted through 3 or 4 pistons; all of the cylinders showed galling; all pistons showed heat damage; some piston rings were broken; and exhaust valves were torched.

I would never rule damage out. A lady here inadvertently added diesel to her Subaru and soon after leaving the station noticed the engine losing power and developing a severe knock.
She drove this car into the Subaru dealership that I worked at and it was still running; although knocking like a bandit and smoking like a grassfire.

The one saving grace for this woman was that the station was near the dealership and that she made it into our lot before trying to force that car a long distance.
A longer distance could very well have destroyed the engine.

There’s a limit to what knock sensors can do. I doubt if they can handle a 50% reduction in octane and still keep the engine running.