UPDATE: gas in car diesel?

Posted by TalTay13@reddit | askcarguys | View on Reddit | 26 comments

So the post went viral I'd say😅

Many asked for an update and pictures of the car broken and destroyed after my brother put gas in a diesel car (and yes, here in Italy there's diesel corollas). Someone even said I'd be car shopping this weekend 🤣<3

Well, the car is completely fine, runs smooth, actually even better than before. No weird sounds or stuff. I didn't syphon the gas out cause I was afraid of damaging it more since I don't know ANYTHING about cars (it was night, couldn't bring it to the mechanic. And plus, I didn't know how to do it properly).

We just topped it with diesel like the mechanic and some of you said. Drove gently today and no problem!

Thanks a lot for all the advice! It was very appreciated and useful!

And rest assured, he'll never drive it again! Hiding the keys as we speak😄

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RickySlayer9@reddit

I did this once in my ford f350. Put 9 gallons of gas in the 36 gallon tank. Realized my mistake and put diesel in.

The gas is a solvent. Diesel is a lubricant. Many parts, like the fuel pump, and injectors on a diesel require lubrication which it gets from diesel fuel, and gasoline actively strips this away.

I solved the issue by just filling it back up to the top every 3/4 tank for the next 1000 miles. It actually ran better.

Diesel engines can run on anything remotely flammable, as far as the physics behind it are concerned. Just worried about the supporting components

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No_Brother_2385@reddit

No, in a diesel fuel system diesel is not a lubricant. It's fuel. For instance, fuel pump moving parts are sealed from the fuel.

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Admiral_peck@reddit

Tell me you've never seen the inside of common diesel injection pumps

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Nutella_Zamboni@reddit

My coworkers think im crazy when I add a little leftover diesel, gas, or mixed fuel to the "wrong" tractor. Never had an issue and I always top off the fuel with whatever it is "supposed" to have. The only think I haven't done is run diesel in a 2cycle.....

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Initial-Reading-2775@reddit

Once I accidentally fueled-up a lawnmower with kerosene. It was nearly flying.

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RickySlayer9@reddit

Honestly I wonder what ratio of diesel to gas would be needed to make a 2 stroke work?

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SailingSpark@reddit

I can see why a small amount of gasoline made it smoother. It thinned the diesel slightly and probably cleaned out the pump and injectors

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Happily-Incorrect@reddit

Got it. Stick a litre of unleaded in my diesel once a month yeah?

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RickySlayer9@reddit

Harmless bordering on helpful

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Admiral_peck@reddit

Depends on what high pressure pump you have. This will quickly kill a bosch cp4 pump

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karlowolf05@reddit

You can just use 2 stroke oil for the same purpose, works great.

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WoodenNet8388@reddit

Instructions unclear, filled my tank with DEF. I should probably pour some sugar in there now to soak up the DEF right? This is for a 2007 Chrysler 300

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ThatPimpAtStarbucks@reddit

You can't ruin a Chrysler 300. It comes factory ruined.

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Forward-Concern403@reddit

makes sense, gasoline does act as a solvent for diesel systems. Just don't make it a habit since long term it can damage seals and reduce lubrication properties that diesel provides to the fuel system components.

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Gubbtratt1@reddit

If an old diesel doesn't pass emissions testing, one of the ways to make it pass is to mix a liter of petrol in the tank.

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Monotask_Servitor@reddit

2L of gas into a whole tank of diesel probably doesn’t change the fuel composition enough to be outside of the range that the engine is designed to be run on anyway. Much more than that and you’ll start to get issues

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Taredmonkeh@reddit

Twenty-year-old diesel engines are indeed rugged; swap in a recent high-pressure common-rail engine and that gasoline might have generated four-digit repair bills. Old mechanical pumps are less finicky about fuel.

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Numerous-Major5878@reddit

It's 2026. 20 years old = 2006, more-or-less all diesel cars had high-pressure injection in 2006. VW was the hold-out against common-rail at that point, using Pumpe Duse -- i.e. one high-pressure pump per cylinder built into the injector, so still a high-pressure system.

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Numerous-Major5878@reddit

Keep topping it up with diesel to dilute the petrol.

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B5_S4@reddit

If you have a high pressure fuel pump, which if it's a modern corolla I assume you do, it may not enjoy the thinner fuel. If you lose the hpfp you'll ruin the entire fuel system. On cars they sell here it's a $6,000 repair. If I were you'd I'd find a diesel lubricity additive and put that in the tank as well.

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JCDU@reddit

2 litres of gas in a 40+ litre tank of diesel one time is not going to harm it dude, I dare say winter diesel is similarly thinned.

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AlaskaGreenTDI@reddit

OP guessed the car at twenty something years old in the other post, so there was some ambiguity of what fuel system it might have.

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SurlyJohn009@reddit

In America, I'm in Oregon. I have had 3 different people I've known put diesel into a gas vehicle. Filled the tank each time as the diesel nozzle fits in the fuel neck on most vehicles. Really bad move.

That can destroy a vehicle engine. You had the opposite, gas into a diesel. Diesel engines are tough as they come, they have to be, no spark plugs to ignite the fuel. Diesels are built to accept the extra pressure needed to ignite the fuel through compression.

I would have siphoned out the gas, but your circumstances didn't allow it. So topping off with diesel is the right move. I'd even go on a long trip, use up most of the tank, then fill with all new diesel.

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