Beware of solidifying screenwash

Posted on January 9th, 2018 by Rob Marshall


An interesting story appeared earlier this winter, where a BMW owner had a manufacturer warranty claim refused, for using an aftermarket screen-wash that reacted with an incompatible type within the car’s washer bottle and caused a blockage.

The owner was quoted saying that the main dealership told him that he should have used BMW’s branded anti-bacterial washer fluid, instead of the supermarket-supplied type that was four times cheaper. When he looked in the owner’s handbook, there was no stipulation that BMW-only screen-wash should be used. I think that this might be because a legal complication might arise. Anyway, the manual did state that different types should not be mixed – something that Auto Express magazine slammed as ‘misleading’ and stated that,

“By this logic, owners should only ever use BMW washer fluid or risk falling foul of this implied warranty clause.”

While this caused a certain degree of outrage and media coverage, BMW neither refunded the customer his £163 invoice to replace the bottle and fine filters, nor changed the words in the handbook. It is a shame that the owner did not commence legal proceedings, because it would have provided a degree of clarification…

Yet, especially at this time year, there is a lesson to be learned – all screenwashes are not equal and, should mixing result in any chemical reaction, the gunge could cause a blockage within the fine filters and tiny jets that are part of a typical modern screen and headlight wash system. Therefore, try to stick with one brand of fluid.


Rob Marshall has served as GEM Motoring Assists’ technical advisor, since 2009, and has provided many hundreds of members with impartial and free one-to-one advice, in their hours of need. He started working on cars from the age of ten years-old and has bought, repaired, traded and sold them ever since. While he holds a variety of mechanical and bodywork repair skills and experience, having worked within the motor sales and repair businesses, he is also involved actively within the motoring media, since supplying BBC Top Gear with a car in 1997. Today, Rob contributes to a wide range of motoring publications, from Car Mechanics to Classic and Sports Car magazine.