Maxol's new loyalty promotion offering money-off vouchers for Marks & Spencer and Argos sounds like an appealing proposition. However, savvy consumers will be quick to spot that they have to spend £500 on petrol or other Maxol products before they earn a £5 voucher for M & S - which makes for a very expensive pair of socks.

This modest 1 per cent return is, surprisingly, standard for the industry, with Statoil, Shell and Esso offering similar returns. Maxol has spent £750,000 developing the scheme which is the first instant electronic loyalty card which will be accepted in both the Republic and Northern Ireland. The promotion will be supported by an advertising campaign created by agency CDP.