dont use the tescos stuff its crap, well not crap but only just better than standard 95 octane and the optimax is better by miles. check out the feb issue of either fast ford or performance ford, they did a comparitive test using 1 engine on the dyno and tescos bp and shell and the shell gave the engine ove 50bhp more than the tesco and could run an extra 13 degrees of advance ignition compared with tescos before pinking. that was infact the third magazine review that ive seen do the test and the results were identical in them all and they all advised that if it is anything but standard dont use teesco fuel