As has already been said, regular oil & oil filter changes are the best way to ensure an engine's long life. I've always halved the interval recommended by the manufacturer, & my Citroën ancienne covered 250,000 miles, sounding as sweet as a nut when I parted with it! The cost of a filter & some oil aren't much, when compared with an engine that runs perfectly for ages. I use Castrol Magnetec 10W/40, without any problems.