Slightly off topic but your oil question initiated this response.
I have owned many cars (36 to date) in my 25 years of driving since passing my test at 17. The one thing I have done with every car purchase (bar brand new ones) is a full service on purchase, then added ZX1 Friction Eliminator to the engine oil, water coolant, brake, steering fluid and fuel tank.
I have never had an engine failure, water pump failure, gearbox or clutch failure, cam belt snap or any other serious problem. I attribute this to this product, this additive is brilliant, it increases fuel effeciency, makes the engine quieter and I believe it genuinely works. It was first formulated for off shore drilling to lubricate the drills but then refined to combustion engines and other applications.
Just my two penneth, I'm sure there'll be some negative posts following this comment............