Friday 20 April 2018

What to do if you put petrol in the tank of a diesel car?

Eddie Cunningham

Eddie Cunningham

What to do if you put petrol in the tank of a diesel car?

LOTS of readers have recently asked what they should do when they discover they have put petrol in a diesel car.

The blunt answer is: get help and advice before you do anything but do NOT turn on the ignition.

There is a school of thought that you'll get away with it if you've only put in a small amount.

But how much is a 'small amount'? A litre, or two or three?

I'm fearful of categorically saying that a small sup will not do damage. I know some people add a drop on purpose to 'reduce' emissions. Let them. I'll tell you what happened to me a long time ago.

I put half a gallon (yes it is that long ago) of petrol into a quarter-full tank of diesel. I then topped up with diesel. I drove 50 miles in fourth gear to keep up the revs and topped up on diesel again. I drove another 50 miles and topped up once more. The idea was to dilute it as much as possible. I had it checked the next day and was told there was no harm done. I took their word for it – but I still don't know.

However, many of today's diesel engines are far more sensitively tuned, balanced and set up so even small amounts of petrol can cause damage.

I have had several emails from people who recently did more or less what I did all those years ago and reported no harm.

However, the strong advice is this: when you realise your mistake do not go into a panic (easier said than done).

Please do NOT turn on the ignition or start the engine – that will push the 'alien' fuel through the system.

Call your garage or mechanic and tell them the exact quantities and circumstances involved. If it's only a small amount, they may reckon you'll get away with it. Every case is different. The age and condition of car, engine etc are crucial factors, obviously.

If it's a good few litres, you'll almost certainly have to get it drained – you have to balance the potential high cost of damage/repairs against the lesser price of draining the tank and flushing the system.

The danger with petrol in diesel is that it reduces lubrication. That can increase damage to the pump because you have more metal to metal contact.

Again: do NOT turn on the ignition until you get advice from a mechanic. That gives you time and expertise before any harm is done. Let me know of your experiences, please. Twitter: #ecunninghamcars

Irish Independent

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