So I've done about 8,000 miles and got an AdBlue/DEF warning the other day, it said I had 1500 mls range left.

I had noticed my local Esso garage selling this stuff for £10.49 per 3.5ltr or £19.99 per 10ltr, which kinda sounded expensive to me. So whilst I was passing Morrison's yesterday I took the opportunity to fill up with diesel (£1.33/ltr - blimey when did it suddenly go up in price, I'm sure it was £1.23 not long ago), they were selling 3.5ltr for £7, so I bought two and the warning has gone now, but it still seems like this stuff is quite pricey for what it is.

Does actual real wee work because if it does I might start storing my own like one of those extreme hoarders you see on the telly!