Many of you i'm sure require fully sythetic motor oil for servicing, top etc..
Mobil 1, is usually the brand by choice but comes at a price! You would normally pay £12.99 a litre, or £40+ for a 4 litre bottle.
Costco, a membership required store, are selling these 4 litre bottles for £21.13.
Unfortunatley, they don't list all their items online, but i'm sure you are all likey to know someone who has a membership card..