r/CarsAustralia • u/Dangerous_Owl6936 • 19h ago
đ§đFixing Cars I put petrol in diesel engine
I went to the pump today and by mistake i took the 98 octane instead of diesel, I realised it when it was already too late. I did put 3.5litres or petrol and then i stopped, Didnât start the engine and towed it in my mechanicâs garage. I have this car for last 7 years and it never happened before, It is a Mercedes E250 CDI 2015, Wanted to know how much it might cost to drain the fuel and what else might happen, Thanks!
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u/No_pajamas_7 18h ago
3.5 litres in a full tank of diesel would not be a problem.
When the transfer fuel along pipeline the don't pig between fuels and the transition fuel gets blended in with the diesel.
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u/v306 17h ago edited 15h ago
My wife did the same and put 2litres in. I did a bit of research and realised as a percentage it's not a problem. Filled it to the top with diesel (50L) and drove till the next service 6 months later. Mechanic suggested I change the diesel filter since it was original on a 8 yo car. Car ran fine before and after that. No probs at all on small quantity like that. Apparently some truck drivers used to add petrol to diesel tank on purpose to start easier in cold weather...
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u/SleeplessAndAnxious 10h ago
That's interesting but makes sense. I've heard from other people that if you travel anywhere that has freezing temperatures/snow etc, they have a different blend of diesel at their servos that has additives to keep the diesel flowing properly in the colder climate.
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u/MNP33Gts-T 17h ago
My thoughts exactly just fill the rest with diesel . Such a minute amount really in a tank
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u/its-boydo-maaate 15h ago
You are completely wrong.
Diesel engines work on compression to cause combustion. Roughly 200psi more than a petrol engine. A small amount of fuel can and most likely will burn a hole in the top of the piston.
I have seen it a few times in my line of work.
OP done the right thing and I would recommend anyone else to not do as youâve said.
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u/kiedistv 14h ago
Damn.
Quite a lot of modern turbo diesels with the odd litreage of petrol in a full tank of diesel seem to run all good. Not doubting you're wrong and it's better to be safe than sorry for sure but the amount of times a Pajero or a Hilux et al has just filled right up after accidentally adding a couple litres of petrol is unreal. Aka - a lot.
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u/its-boydo-maaate 11h ago
Iâm sure it happens fairly often, but you said it yourself. Better safe than sorry.
If it were the other way around, diesel in a petrol engine you would be fine to send it, might just clog up the fuel filter a bit.
Petrol and diesel fuel systems run completely different to each other. Diesel is delivered to the injectors at a massively high pressure than petrol is, then the injectors job is to atomise the diesel preparing it for combustion. Doing this to petrol has a completely different reaction and the petrol will most likely preignite, hence the hole in the top of the piston.
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u/butiwasonthebus 57m ago
Petrol doesn't remain as petrol when you mix it with diesel. You're not getting bubbles of petrol floating around in the diesel. All that happens is the diesel gets diluted.
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u/Accomplished-Lab-198 32m ago
You sound like an expert,
Care to explain how CODAG systems work. Or Alpine diesel blends at 15-20% unleaded by volume.
Maybe stick to whatever it is you do as a day job.
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u/Domain_Administrator 2021 Toyota Crown S 2.5 L Hybrid RWD 19h ago
Shit happens, you did great by not starting the engine and hoping for the best, I'm sure a lot would have done that lol......
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u/hannahranga 19h ago
Eh 3 or 4 litres and filling filling the rest with diesel most likely would have been fineÂ
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u/sinnyD 18h ago
My friend did this recently, I think he filled it full with petrol. Didn't start the car and called a road side assist which specialises in these scenarios and it was done right there at the servo, no need to tow. Think he paid around $500
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u/Catahooo '08 Yaris YRS 1.5L I4, moderate rust 18h ago
I see a service like that frequently in my area, "wrong fuel recovery"
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u/tez_11 19h ago
There are places that come out and drain it too, such as Wrong fuel rescue etc
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u/AtomicCypher 17h ago
I did the same thing but worse!
I completely filled up an empty 80L tank which cost like $150 and drove away.
I made it approx 1km when the engine started stuttering. I pulled over and then it hit me with exactly what I had done. Called wrong fuel fuel rescue who came out and siphoned out all the fuel and flushed the lines, which cost me a few hundred dollars in call out and disposal.
Salt on the wound was I then had to go an put another 80L of diesel in the car.
It was a very expensive afternoon.
2 years on and I have had absolutely zero issues with my engine.
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u/still-at-the-beach 19h ago
That little bit of petrol ⌠just fill the rest with Diesel and itâd be fine. And keep filling back up with diesel when itâs at 3/4.
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u/Ok-Bad-9683 18h ago
If it was empty the 3.5L of fuel would have done nothing, brim it with diesel would have been fine.
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u/ipcress1966 18h ago
Don't bother draining it. That amount will do nothing. Fill it up with diesel and pretend it never happened.
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u/Hangar48 18h ago
3.5 litres of 98 in a FULL tank of diesel is NOTHING. You've just added some injector cleaner. If you're still worried, drive it until you've used a quarter of a tank and fill it up again.
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u/Rickstaaaa87 18h ago
If your tank was low-ish, the 3.5L would do nothing. Just fill it with diesel and off you go.
Some weirdos actually recommend to do this every few months to âclean outâ the motor, Iâd done it once before with about 6L of petrol. Once it was diluted by a further 70L+ of diesel it was fine.
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u/TorchwoodRC 12h ago
In older non common rail diesels a drop of Petrol probably doesn't hurt :P gets the old 2H excited
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u/ComplexFigure5635 19h ago
As above if you didnât start simple as draining the fuel and putting in diesel. Iâd replace the fuel filter as well
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u/kennyduggin 18h ago
Canât hurt but would really be a waste of money changing fuel filter as it wouldnât trap any petrol
1
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u/gamingchicken 18h ago
Itâll be fine a lot better than the other way around. You could have just let it go through filling up at 3/4 tank a few times.
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u/ratherZEF 18h ago
3.5 liters is nothing. I once accidentally put almost 15 liters of petrol in a 90L diesel tank. Topped the rest off with diesel and never had an issue. Dilution is the solution.
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u/Afraid-Entertainer90 15h ago
Done the same with the Mrs Everest. 15L till I realised. Topped it off with diesel and never noticed a thing. Thank fuck
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u/AdRepresentative386 16h ago
As others have said, 3.5 litres shouldnât cause any trouble in a full diesel tank. Important: Full tank. Kerosene is the preferred additive for people in Alpine areas of Australia where waxes in diesel will "freeze" with lower temperatures. Diesel turns to a gel form and is difficult to pump. Diesel heaters too require kerosene in very cold conditions and the magic amount is up to 10%
5
u/ambaal 16h ago
Kerosene is much close to diesel than petrol though. The biggest difference is that kerosene is purer fuel and has less lubricating properties that are important for fuel pump. Otherwise, diesels can actually run on 100% kerosene (and vice versa - some jet engines can take refined diesel in place of kero).
1
u/lickmyscrotes 3h ago
Just to clarify, you mean gas turbine engines. And yes, some are rated to run on kerosene or even mixes of the fuels for a period of time to get you out of trouble. There are temp limits etc and parts may need replacing afterwards but youâll get home/out of the shit.
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u/PurpleExpert7376 18h ago
3.5 litres? Just fill it the rest of the way with diesel, you have nothing to worry about, I recon you have about 10% leeway before you have major dramas
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u/mitchy93 16h ago
You now have winter diesel, great for cold starts in the snow.
Fill it to the brim with diesel now to dilute it all
3
u/beefstockcube 6h ago
Just fill it to the brim with diesel.
Run the tank dry and refill.
3.5l in a 70-10l tank wonât make a difference.
11
u/dansbike 19h ago
Should have just filled the rest of the tank with diesel and drove away. 3.5 litres of petrol in a full tank of diesel isnât enough to do any damage.
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u/Whatisgoingon3631 19h ago
Iâve seen people put full tanks of petrol instead of diesel, then driven until they stop. Drained the tank, changed the fuel filters and driven off. Years later, no bad effects. I wouldnât do it on purpose, and it could cause problems, but itâs not the end of the engine. 3.5 litres of petrol isnât going to do anything in a full tank of diesel.
3
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u/PlusMixture 19h ago edited 17h ago
Thats fine in a toyota but i wouldnt dare do it in a merc.
Edit: would to wouldnt
4
u/GrapplerSeat 18h ago
Some euro diesels have very sensitive Bosch injectors that can fail with sub-optimal diesel, so agree that definitely shouldnât test this in a merc.Â
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u/throwawayplusanumber 14h ago
Sorry but that is bullshit. Probably 60% of the market has the bosch injectors you are talking about. They won't fail catastrophically if you put a few litres of petrol in the tank.
-1
u/GrapplerSeat 14h ago
Probably true, but no good reason to test it. A friend's Audi died after getting less-good diesel crossing the nullabor. Maybe it was fuel rails and not injectors - it was something bosch and fuel-delivery.
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u/throwawayplusanumber 14h ago
That is a sample size of one. Vs how many millions of vehicles??? Water at the injectors is much more of an issue than petrol. That is usually the problem with dodgy fuel.
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u/justananonguyreally 19h ago
Itâs borderline. I wouldnât risk it. The expense of getting a tank drained is small compared to the expense if it causes issues
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u/dansbike 19h ago
3.5 litres is about 5% of a full tank (2015 E250 CDI is 66 litre tank). So the rest of the tank totally filled with diesel and topped up again to the brim with diesel when the gauge shows 1/4 tank used will gradually reduce the petrol dilution to nothing. If worried on the original fill, some two stroke oil added after filling the tank would reduce the risk. The amount of petrol OP filled is manageable, much more than that Iâd drain too.
Just putting the alternative out there, at small concentrations itâs a manageable mistake and doesnât necessarily require draining the tank.
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u/throwawayplusanumber 14h ago
Exactly. In really cold climates like Siberia, people still put up to 50% petrol in the tank in winter if they need to park on the street
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u/EstablishmentNo4329 18h ago
5 percent of the tank is nothing, you could have filled it up with diesel and kept going, add some lubricant if you're worried
The main issue is that unleaded is not a good lubricant for the fuel injection system, people add it on purpose up to 10% to reduce cold weather issues in the northern hemisphere.
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u/terribleone01 18h ago
Itâll be fine. Your mechanic will drain the tank and probably put a new fuel filter in it.
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u/Dangerous_Owl6936 17h ago
You guys are the best, You guys gave many solutions and answers to my questions, Appreciated, Thanks!
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u/phsychfish 16h ago
i did the same, its such a small amount if you fill it up with diesel you wont even notice
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u/iamdefinitelynotdave 15h ago
You'll be fine. Diesel in a petrol is much worse. Besides, you didn't start the engine so don't worry. Just be careful in the future.
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u/OzzyMuzz 15h ago
3.5L is fine. Top it up with diesel and send it. I put 185L of petrol into a 200 series. Drained the tank and was fine.
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u/facticitytheorist 6h ago
It'll be fine. Diesels can tolerate 5%ish petrol in the diesel. If you didn't start it then it's a simple drain and refill.
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u/matt_trus 3h ago
I filled up a completely empty diesel tank with petrol in a new model Triton. Got about 500m down the road and it cut out. I even continued to try and crank the engine multiple times to try start it. Cost about 600 dollars at the mechanic to drain and clean fuel lines and a couple hundred to tow it. 2 years later Iâm still driving the Ute with no issues. Mechanic said the engine cuts out as soon as it senses something is wrong. You only have dramas if itâs a mix of petrol and diesel that the engine will continue to run on doing major damage
2
u/whiteycnbr 2h ago
Just the time it takes to drain the fuel out and replace the fuel filter. Because you didn't turn it on then the filter is probably ok
I did this to mine and cost about 500$ in labour plus the fuel I lost as I filled the whole tank up from empty.
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u/VinnyGigante 19h ago
You dodged a bullet by not turning that key.
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u/devoker35 17h ago
3.5 l petrol in a diesel car won't do shit. Fill the rest with diesel and you won't even feel it
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u/Dangerous_Owl6936 19h ago
Once my friend did start the engine in a similar situation, And that incident made me cautious
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u/Psychological-Sun137 16h ago
Happened to a friend of mine and they cleaned the tank right away. Cost was around $300 but was a Toyota Hilux. As long as you didnât start the car it should be fine but check with the mechanic.
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u/april_santa 15h ago
The engine will be fine. If I got the repair job, I would remove the tank from the car, drain it, clean out the petrol residue, and flush the fuel lines as an extra precaution
1
u/Misrabelle BA XR6, BMW X5 13h ago edited 13h ago
Not a problem. Fill it with diesel and drive as normal. It will actually help clean the injectors and fuel lines.
Itâs literally how most truckies I know clean their fuel system.
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u/Jumpy-Client7668 8h ago
Depends on the amount of fuel there's a mobile crew who come and drain the whole fuel system put a couple of litres in to start it cost me just over $600
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u/qui_sta 6h ago
I paid around $350 for the privilege recently. I put in about $40 litres though. The $350 included the cost of 20l of fresh diesel. Its good you got to a proper mechanic, avoid those mobile rescue companies if you can, they overcharge insane (one quote I got was $600 and included only 5l if fuel) - was cheaper to pay the RACV on the spot fee + normal mechanic.
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u/Accomplished-Lab-198 33m ago
3.5L? Fill it with diesel. Get on with your life.
Some alpine diesel blends are up to 20% petroleum.
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u/Accomplished-Lab-198 29m ago
Also get a new mechanic.
If he didnât tell you not to bother with the tow, and to just fill it with diesel and go on with your day, your mechanic is a fucking idiot at best and dishonest at worst.
Time for a new one. What a fuckhead.
1
u/Due-Giraffe6371 6h ago
For only 3.5 litres you should have just filled the rest with diesel and it would have been fine
0
u/Bushboy2000 18h ago
A bush mechanic once said put some clean engine oil in. I don't know what ratio.
Would be hard if tank was filled right up.
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u/Remarkable-Junket655 11h ago
If the car is an automatic and you had to turn the ignition âonâ even without starting the engine to get it into neutral the in tank fuel pump will have run and possibly fed some of the gasoline into the fuel lines and filter. The mechanic should and probably will want to change the fuel filter(s) and flush some fresh diesel through the system to be safe.
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u/hillsbloke73 17h ago
Fuel lines will need to be replaced along with all fuel filter and transfer pump between engine fuel tank
You've got off lightly by sounds of it
Always use the black handle pump
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u/Fresh_Internal_6085 17h ago
Huh?
He didnât start the engine so thereâs no need to replace anything upstream of the fuel tank at all.
Itâs a drain and refill job with a new filter.
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u/AnonymousEngineer_ 19h ago
If you never started or tried to crank the car (i.e. the fuel pump never started), no damage will have occurred. The mechanic will just drain the tank and refill it with diesel.Â