Engine Oil Additives ?

[man of kent]

Originally Posted by Richiemd

Well this is confusing I've just started the car to see if the Waste fuel recirculation system was the tapping I could hear but when I started the car the tapping had stopped ,is it possible the oil and filter change has had a positive affect on the engine ,it had a two hour journey last night ?

Dont forget that as the 'thickening' polymers in the multigrade oil wears out the oil viscocity drops i.e. 10W 40 might be 40 on a motorway running hot but after a lot of miles it might only be 30 or even less. Thats why you have to change oil. I remember when multigrades first came out it was just 10W30 and some engines blew up on motorways because the 30 was too thin especially the long stroke ones like the Ford 1200cc 4 cylinder. (Another reason why long stroke engines are not popular - the piston velocity is so high)Then came the 20W50 to make the oil thicker. Now of course the oil is so much better you can run 10W30 or even 5W30 on new engines. Dont forget that very high mileage engines and especially poorly serviced ones need a thicker oil. It basically fills the worn bearing and ring gaps up! Oil thickness affects the hydraulic tappet clearance so changing oil will change it.