Mis-Fuel Advice

[lharker]

I have just mis-fueled my 2010 xc90 with unleaded, driven 1/2 mile home and realised my error. Is it ok to drain the fuel or should it go to a garage? Advice also please on the location of the fuel drain bolt. Thanks in advance for any advice

[jimmy57]

You mean you fueled it with reg instead of premium. If that is it do not worry. The fuel requirement would only cause any problem if you are climbing steep grades. The engine power ratings are established with premium. The engine computer calibrations are set with premium. When lesser grade fuel is used the engine computer will adjust for the lesser octane but this will result in reduced power in some situations. Your driving style and the temperature and load of vehicle may make the adjustments noticeable as a slight hesitation. I run lower grade in my vehicles and have for hundreds of thousands of miles, for money savings and the diminished performance is no bother. I usually have no diminished performance that is noticeable except on rare occasions. Do not worry. If it bothers you or you notice anything then fill it with premium when it drops 1/4 tank for a couple of fuelings and the regular will be diluted enough to eliminate any possible compensations for the lesser octane.
Your owner's guide RECOMMNENDS premium for the best performance. There is no text saying you need to visit workshop if anything less is used.

[billofdurham]

lharker, welcome to Matthew's Volvo Site.

I suspect that, as this is a UK car, it is diesel and you have filled up with unleaded. AA statistics estimate that at least 150,000 drivers put the wrong fuel in their car each year – one every three and a half minutes!

If my assumption is correct the advice is not to start the engine.

Diesel fuel pumps operate on very fine tolerances and are lubricated by the diesel fuel itself. Petrol in diesel acts as a solvent – it reduces lubrication and can cause damage to the pump through metal to metal contact.

Some fuel system seals can be affected by the compounds in petrol too.

The further the contaminated petrol goes in the system the more expensive the repair – it can be cheaper in more extreme cases to fit a new engine.

The newer common rail (or HDi) diesel engines are particularly vulnerable – if fuel contaminated by pump wear debris gets as far as the common rail system you may have to replace the low and high-pressure fuel pumps, injectors, fuel rail, line filters and the fuel tank too.

Many systems use a low-pressure electric pump in the tank or sender unit and this begins to work as soon as the ignition is switched on, circulating the contaminated fuel through the pump and rail – so it's important not to turn the ignition on.

I have posted the worst case scenario as a warning to others.

Let us know if my assumption was correct as there is more advice if you need it.

Bill.