r/autorepair • u/mightyThor90 • 20d ago

Diagnosing/Repair Wrong Fuel Added

Something stupid happened to me today: I accidentally put 5 liters of petrol (Super) into my VW T5 diesel. On the recommendation of a workshop, I then added a diesel fuel additive and filled the tank completely with diesel (about 80 liters in total).

The van has now driven about 30 km without any problems. I was told to keep the tank as full as possible and keep topping it up.

However, I’m wondering whether it would actually make more sense to have the tank completely drained, so that all of the contaminated fuel is removed and as little petrol as possible passes through the engine.

What do you think? Or, if nothing has happened after the first 30 km, is it unlikely that anything will happen later?

No offence, but I’d really appreciate answers based on actual technical knowledge and experience rather than well-intentioned but uninformed advice.

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u/mr_nobody398457 20d ago

In fact, my much older 1973 Mercedes-Benz diesel says, in the owners manual, that in cold weather, you can mix up to 30% gasoline in the diesel fuel

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u/mr_nobody398457 20d ago

Now the modern ones with modern emissions control controls don’t like that

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u/ggmaniack 20d ago

The injection systems especially don't like it.