ive got a 96 cinq sporting . ive had 3 weeks and now that ive filled it up the petrol gauge is dropping like mad. its showing just over 1/4 tank but ive only done 140 miles since this . im a new driving so i havent been razzing around or any thing like that. could the gauge be screwed or is the sender unit in the tank be badly designed . theres no smell of leaking petrol. also what sort of milage should i be getting from a full tank , im reckoning about 3/350 miles total, or is that just mad.