Leaderboard

A bad cheap battery won't damage your electronics but may cause issues and throw up a lot of electrical trouble codes. It won't last as long and could leave you stranded. Rather than disconnecting a battery if you're not going to use the car for a while, I recommend using a battery conditioner instead. They aren't expensive and you can get solar ones if you have no mains power supply. Disconnecting in modern cars can cause all sorts of problems which can lead to a lot of things having to be reprogrammed.

Money spinner for service stations IMO. The fact that it says on the bottle to use it on a mileage as small 4K says it all. They want you to buy loads of it. Garage I used to work in sold it. I gave a few bottles to friends to try as an experiment and had no positive results that would make me want to pay for and put it in my own car. The only real way to clean injectors is to remove them and clean them manually. As for cleaning valves and pistons, you can try terraclean or snowfoam but using plain tap water will have the same results at zero cost. Look on YouTube, there's a few videos on decarbonising your engine with water. There was a thread on here about it a while ago too. If you want your valves to really look like new, you need walnut blasting. I don't know anyone here who does it.