This might be more popular than the last deal I posted for the 4.5 litres Asda smart price oil :)
2 litres of Castrol GTX 10w-40 oil £3.98. Therefore £7.96 for 4 litres - a rip off £19.99 in Halfrauds for same amount, or normally £12.87 in Asda stores that sell the 4 litre cans.
They also had: -
GTX Magnatec 5w-30 2L £6.71
GTX Diesel 10w-40 2L - £4.39
General rule seems to be all oil in Asda living is half price, at least in the Leeds Crown Point store.
To find your nearest ASDA living store, click "go to deal" and type in your location and select "ASDA Living" and it will tell you your nearest store. There appear to be 16 of them across Great Britain. Basically it's an ASDA without groceries and more clothes and tellies etc.