Castrol GTX 10w-40 four litre available in my local tesco petrol station for just £7.88.
The 2l was £10, and I spotted the 4l marked up as £12, so took it the till to pay, and it rung through at £7.88. Woman in there said it had been that price for a while.
Went back and picked up another at that price...
top bargain... hope it helps someone.