1 gallon of gas weighs about 6lbs, so 7x6=42lbs and in the other 105lbs
so.. 3642 vs 3995.. whats the deal with the person racing with cement bags in his trunk?
don't let anyone make excuses about full tank + stuff in their trunk.. that's ricer style excuses. full vs half tank you are talking about a 50lbs difference generally, no big deal really. yeah if you are chasing an ET at the dragstrip you'll want to shed every lbs you can, but in street racing it wont make much of a difference. if you lose very slowly where they are inching away on you, yeah you might have wanted to take the cement out of your trunk.
but a full tank vs half full tank, maybe if you had a 90lbs jockey driving your car you'd win too eh?