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A businessman who borrowed a friend's luxury car and filled it up with the wrong fuel was left facing a whopping £15,000 repair bill.

Alan Thompson borrowed pal Elizabeth Moulton's Porsche Cayenne SUV for a weekend and to say thank you, courteously returned it with a full tank of fuel.

Unfortunately his good-will gesture backfired spectacularly, after he brimmed the £47,000 car with petrol, unaware that the sporty 4x4 actually ran on diesel.

Mrs Moulton immediately noticed the car was in poor health and quickly drove the spluttering Porsche to her local dealership in Stratford, East London, where she was left shocked and angry after being presented with a quote for £14,600 to fix the damage done.

Speaking to the Daily Mail, Mrs Moulton said: "I was dumbstruck when I was told the cost, I didn't know what to say or do. I couldn't be furious with Alan but I was furious with Porsche. I just thought 'for goodness sake'."

She then approached other official Porsche dealers and received quotes ranging from £5,000-£10,000.

She later had the remedial work carried out at a local garage for a much more reasonable £1,000.

Mr Thompson has since accused the German manufacturer of attempting to fleece the pair.

'We all make mistakes but I do object to being ripped-off to such a ludicrous extent by Porsche who I have found to be unsympathetic, inefficient and unhelpful," the blundering 64-year-old complained.

"It is a common and very easy mistake to make when especially when you get to my age, when one frequently makes mistakes."

However, Porsche has defended the eye-watering quote, which included replacement of most of the car's fuel system, as a recommended measure to prevent further damage to components sensitive to the wrong type of fuel.

However, the garage that undertook the work merely removed the fuel, changed the fuel filter and flushed the system with detergent before re-filling the tank with diesel.

Costing a grand total of £1,103, the work has left the car driving as it was before the fuelling mishap, according to Mrs Moulton.

Around 120,000 absent-minded motorists fill their car with the wrong fuel each year, with each case typically resulting in costly repairs. A number of manufacturers are now fitting devices to prevent the wrong nozzle from being inserted into the fuel filler pipe.