I don`t know if this is only a local reduction but my local asda are doing Castrol Power 1 4T 10/40 for £5.00/L. Usual price appears to be around £30/4L or £10/L.
It's in my local Asda, and it is a good price. But note that this is the regular Power 1 4T semi-synthetic and not the Power 1 "Racing" which is fully synthetic. Interesting that the shelf label at Asda says it's reduced from £7.50 to £5, but it's £10 at Halfords.
