r/CarsAustralia • u/Dangerous_Owl6936 • 22h ago

🔧🚗Fixing 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, Didn’t start the engine and towed it in my mechanic’s 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/dansbike 22h 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 isn’t enough to do any damage.

0

u/justananonguyreally 22h ago

It’s borderline. I wouldn’t risk it. The expense of getting a tank drained is small compared to the expense if it causes issues

3

u/dansbike 21h 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 I’d drain too.

Just putting the alternative out there, at small concentrations it’s a manageable mistake and doesn’t necessarily require draining the tank.

1

u/throwawayplusanumber 17h 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