Petrol in a diesel van - what should we do?

My son in-law put 1/4 of a tank of unleaded petrol in his Fiat diesel van before realising he had made an error and then filled up with the correct diesel fuel.

He has driven the van since and has two conflicting pieces of advice on what to do now: one garage says he must stop driving the van and have the tank and system drained - at a cost of £150 - and the other, an independent mechanic, says the ration of diesel to petrol makes it less critical and he can continue driving but not to over rev the engine but to add upper cylinder lubricant regularly. What do you suggest he

Asked on 15 January 2014 by Neil of Three Oaks

Answered by Honest John
I have got away with 10 litres of petrol in a 60 litre diesel tank. Absolutely critical to keep adding lubricity additive, run only on Shell V-Power Nitro Plus (because it has the most lubricity of any diesel) and never to let the tank go lower than half full. The reason for that is that the lighter petrol will float on top of the diesel until it gradually gets dispersed into the diesel. This could take 2,000 miles. But I can't guarantee this will work so if he is worried he should pay to have the tank drained.
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