Does anyone use different grades of oil in the summer/winter? My grandad always used to but I've not really seen the point of it with modern multigrade oils.
There is no need to change oils for winter and summer, especially in the UK where the winter/summer temperatures are not that far apart compared to some more brutal parts of the world.
What is important is that the oil stays in grade during its service life. Full Synthetics are hard to beat in this respect, but even some of these can be mis-described. For example Castrol's Magnetec stuff is based on sytheteic technology. It is not a fully synthetic oil. Interestingly, Mobil 1 is the same!
I've long been a fan of Millers oils but have recently defected to AMSOIL's newly introduced fully synthetic 5w/40 diesel oil.
Some cars are running 0w/30 or even 0w/20 oils now, which are incredibly light. I sometimes wonder if fuel economy is championing over engine life but I have no evidence to back up this thought.
Don't be tempted to use oils of a higher viscosity than specified. You'll get poor cold circulation and when hot the oil film can actually tear away from moving metal parts because it's too viscous.
Don't blend viscosities to create your own oil - the additive packs are totally different between grades even from the same manufacturer. And don't mix synthetics with those from other manufacturers even of the same grade. I know of a Jaguar S-type that siezed at less than 20,000 miles as a result of this!
Likewise, aftermarket additives are definite no go areas. The only exception is flushing agents, although they shouldn't be used unless you have a specific contamination problem. The only way to diagnose such an issue is to send an oil sample to a lab for analysis.
There's a good guide here;-
http://www.carbibles.com/engineoil_bible.html
RGds,
Paul.
