Further to your letter from Dan Deakin, he was correct in saying that you do not add petrol in any amount to diesel fuel. I do recall the recent quote from a service manager of an Audi garage saying that it was in a handbook from Audi to add petrol. I was also a service manager in the 1980s, but I never read this. But, if it was written, then I would suggest that there was a confusion in translation, as paraffin in German is sometimes translated as petroleum. In my career, I was a service manager for many franchises, including VW/Audi, Peugeot, Dodge Trucks, Vauxhall and Fiat and I can recall from my truck days that adding paraffin at the rate of five per cent to diesel was in order, with no long-term problems. Adding petrol is a definite no though – any warranty claim, even months or years after, would be voided on any fuel system component that failed and after examination showed any suggestions of petrol damage, whether added by accident at the pumps or otherwise. I have seen very expensive repairs to vehicles, even complete engine replacements, costing thousands of pounds, because petrol had been added. With the current fuel additives, it is not the problem it was. I have run diesel cars since 1986 and not had any problem, and all the vehicles that I have dealt with have not had any issue (other than the accidental fill up). Hope I have added to the debate, and keep up the good work in your excellent section of a brilliant magazine which I have purchased since 1990, and look forward to the arrival every month.
Bill McWhinnie
I think I made it clear that this was a historical situation, and I did not by any means suggest that one should do this today. I hope that it did not read that way! But maybe your suggestion that something was lost in translation in the owner manual is the correct answer. Good thinking Bill.
I guess that I’d better not tell you about when I put some petrol in an A4 1.9 TDI in around 1998, when I had a brief and rather inglorious career working as a sales executive at an Audi dealer. Those mechanical fuel injection engines were a bit less fussy, fortunately, and I think they just towed the car back to the garage (from where it had given up on me), drained the tank, refilled it with diesel, and put it back on the sales display! Always good to hear from long-time readers, and I hope that we can continue to deliver you both entertainment and enlightenment. There’s a huge database of knowledge and experience in our readership though, and it’s great to have information travelling in both directions. Best regards and thanks.
Doc Diesel
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Paraffin was added for anti-waxing protection of diesel fuel in winter driving.
Also drivers of Vintage or Veteran cars with driver-controlled ignition advance/retard systems found modern petrol formulations unsuited to their cars, and were advised to add paraffin to the petrol mix to improve driveabilty