I was a little concerned to read that a Ford dealership in Bristol had consulted with Ford, and suggested that seized spark plugs could be “smashed out of the head”. Why? Hardly good engineering practice. The problem with spark plug seizure is very common. This first came to my notice about 15 years ago, when my technicians experienced difficulty in extracting plugs from early Fiesta iron cylinder heads. Evan in those days it was apparent that if the plugs were removed more regularly than the service interval suggested, and the threads lubricated they could easily be removed at a later date without difficulty. On examining the plugs on later Ford models it was apparent that the plug manufactures are reducing the wall thickness of the spark plug, this with the corrosion found due to water and other pollutants, is eroding the thin wall of the plug and making them difficult to remove a times without damaging them. The majority of vehicles that we service do not suffer from this condition as we ensure that all vehicles serviced by us from new have their plugs removed and lubricated well before replacement is necessary. Most of the vehicles that come to us these days with plug seizure have been serviced by independent repairers, who have no knowledge of this concern, and therefore fail to apply thread paste. Many of these vehicles have been affected by water dripping from the washer pipe as you suggested, but many more are damaged by water leaking via weeping core plugs in the head. A good percentage is used vehicles, these have been steam cleaned around the engine bay and have water in the plug wells. We have developed our own process and extractor to remove stubborn plugs, we rarely need to remove heads these days, and if we find this necessary we carefully spark erode the damaged plug from the head without damaging the cylinder head itself. I had also been intending to write to you for sometime about a pet subject of yours, frequent oil changing, this is obviously very sensible but any benefit from this is frequently negated. In particularly by fleet operators and hire companies using independent dealers these days to reduce service bills. These independents are not using the correct specification oil in turbo charged diesels engines that use exhaust gas after treatment systems. This frequently leads to repeated turbo failure on these vehicles, which the manufactures are reluctant to cover under the terms of the vehicle warranty.