I agree that frequent engine oil changes are the secret to a longer engine life as this helps to get rid of all the impurities which stop the oil working. But. 'Anti-friction' additives can also have a beneficial effect on top of this - but not instead of it. Molyslip used to be a firm favourite (molybdenum disulphiode) and is slippery in the same way as graphite is. Slick 50 is PTFE (teflon) particles and works a bit better than moly. Either of these used with a good oil (Duckhams) changed regularly is going to give you better than average lubrication and protection. An even better anti-friction additive is called 'Active-8'. I first came across it at a motor show and the demonstration, which you do yourself, is more than just convincing. I have since repeated it at home for friends and this stuff is actually much better than either moly of teflon. It even works suspended in water instead of oil, so you can use it in your coolant to lube your water pump. The only reply I can make to those who dismiss it as 'snake oil' (without really knowing) is that they test it for themselves as it is quite easy to rig-up a demonstration at home. Since I started using it, about 2 years ago, both my Jaguar and Mercedes have returned about 1 mpg better than on Slick-50 - and that was nearly 2 mog better than on pure oil.