When I had my Audi serviced by a local VAG independent specialist recently, the technician told me that they use Castrol 'Edge' fully-synthetic oil for their oil changes as do the franchised dealers. This oil is buttock-clenchingly expensive to buy. (£13-17 per litre is not unusual).

As I like to carry a litre of top-up oil with me when touring (just in case) I searched eBay and bought a 1L bottle of Edge 5W40 for £9.50 which, at the time, I thought was a good price.

However, while filling-up the wife's car at Tesco this morning I saw a display rack of Edge oils all at 25% discount making 1L of 5W40 (for petrol engines) £9.00 (other grades were individually priced).

The offer ends 20 February.