[QUOTE 5325228, member: 9609"]and the rapidly increasing cost of fuel would suggest your money is best kept in your tank, although I suspect the extra rolling resistance due to the weight increase would work out a little more.
typically 40% of your fuel goes on rolling resistance, so an extra 30kg of fuel in a vehicle weighing 1200kg =2.5%, 40% of 2.5% =1% ~ 8000 mile per annum at 50mpg (£1.25 a litre) so that extra fuel is may be costing you £9 year to pointlessly haul about. not much really - BUT - if all 30 million cars on our roads were doing that then that works out at an astonishing 500,000 tons of CO2 pointlessly being created. (which is about the same CO2 savings of over a 100 wind turbines))[/QUOTE]
I'm no physics major but I think that bit in bold seems dubious so any inference from its calculation is probably not correct (probably, because there is a chance one can attain the correct answer but by using incorrect maths, just by chance).