Hell Razor5543 wrote:Fair comment. If you were to get Citroëns' specification requirements for the spark plugs, and take them with you, you can prove ECP gave mis-leading information (especially if you were to print out the details from the ECP website, and drive to their location in the Xantia in question). The exception would be if the plugs they supplied superseded the original spark plugs.
You shouldn't need to go quite that far - a print out showing that type of plug was recommended by their website should be all that's needed.
There are dozens of variations of each spark plug family where most of them are "compatible" to varying degrees, for example different heat ranges, whether they have a resistor or not, electrode number and material etc... They might not last as long or work as well but you probably wouldn't be able to get a refund just on it being a slightly different heat range than recommended for example.
But taper seat versus gasket seat is pretty clear cut - they're not mechanically compatible and could cause engine damage long term (burning at the very narrow contact point) so there is no doubt that they mis-sold them if indeed a number plate/engine search on the website told the customer to buy that type.
I'd certainly phone to complain to get a refund if it was me, more on principle than for cost reasons. It might also prevent some other innocent party buying and fitting the wrong spark plugs if they're made aware of the mistake...