Originally Posted by
haz87
5w40 is far too thin for a cvh really. 10w/40 at the VERY minimum, 15w40 being the normal start point for most owners
I do not agree with this statement at all.
5w40 will be thin at low temperatures (which one wants). It will be a similar viscosity at 100C to 15w40.
I am sure temperatures in the UK get near 0 C. I would not want to start an engine at 0C with 15w40.
In the hot summer (if there is such a thing in the UK) 15w40 would work fine.
In any case, at operating temperature of the engine at 100C or close, 5w40 or 15w40 will have the same viscosity. One just provides better cold start up protection.
When I was road racing with the Cosworth 3 liter Pontiac IMSA engines we ran 20w50. Even on hot days we preheated the oil with a plug in heater before we ran the engine.