OIL COMPANIES. Buy twenty quid’s worth of groceries at Safeway and you’ll be given a voucher for 20p off a litre of petrol. Send one of your tankers and fill it up with 20,000 litres and save 4 grand. Then sell it at your own petrol stations at the normal price. Safeway are in some disarray at present and are unlikely to work out your scam, and you won’t have to rob your employees pension funds to boost up your profits.