A BMW driver was accused by the car giant of wrecking his wiper system by using a cheap supermarket screen wash.
Simon Raeburn took his £40,000 motor in to be fixed under warranty after the jets packed up.
The dealer said he blocked them with a 50p-a-litre fluid from Morrisons instead of using the firm’s own make which is nine times more expensive at £4.50 a litre.
Simon was charged £163 to flush the system and install a new fluid reservoir and strainer in the BMW 335d he bought new less than three years ago.
Simon, 60, of Tavistock, Devon, said: “They told me I should have been using BMW’s anti-bacterial washer fluid and should the jets be blocked the warranty would not apply.”
He checked his manual after reluctantly stumping up at Plymouth dealer Ocean.
It did not stipulate using any special product — only that different ones should not be mixed.
Simon said he always used Morrisons fluid.
Car mag Auto Express slammed the “misleading” manual.
It said: “By this logic, owners should only ever use BMW washer fluid or risk falling foul of this implied warranty clause.”
BMW said: “It’s imperative that the correct concentration of washer additive is added during all top-ups to the screenwash reservoir.”