View Single Post
Old 07-22-2008, 11:07 AM   #82

theholycow's Avatar
Drives: '02 GMC Sierra, '80 Lesabre
Join Date: Mar 2008
Location: RI
Posts: 1,804
Originally Posted by azfan View Post
I must say i am severely disappointed in the cars weight. gas is $4 a gallon. if the V8 gets 15/23 mpg, remember that is even with cylinder deactivation. and that 23 is if you hold steady at 55 mph. what about 65-70? 20 mpg?
i remember when the mustang gt 500 came out at 13 pounds shy of 4,000 i mocked it.
I've been studying this for a while, looking at theory and real world results when people add or remove weight. A few hundred pounds on a nearly two ton car makes ZERO difference in fuel economy. In fact, if you drive reasonably, even larger percentages of weight make zero difference. The main reason that lighter cars get better fuel economy is that they can have smaller, more efficient engines and/or taller gears.

If you accelerate hard all the time and never take your foot off the gas until it's time to shove the brake pedal into the floor, and do a lot of city driving, then a 20% weight difference could give you a measurable fuel economy difference.

As for highway mileage, which seems to be your concern above, weight has almost no bearing on it. Highway mileage is almost 100% about aerodynamic, tire, and drivetrain drag. Even engine size doesn't matter much (with good gears) because large-displacement engines can make the same power at lower RPM, and engine drag goes up exponentially compared to RPM. Blame the aggressive look and the huge ballsy grille of the Camaro for its highway mileage. If it looked like this and was properly geared it would get over 50mpg for sure:

Edit (2008-10-23): Further study has revealed that weight loss can help fuel economy in one situation: A very lightweight car that is severely underpowered. In such a case, it seems that for every 1% weight change, you could see up to or slightly more than 1% fuel economy change.
Removing weight has surprisingly little effect on fuel economy
Engine break-in procedure | Gear ratios
2002 GMC Sierra 4x4 5.3 (190,000 miles and going strong)
1980 Buick Lesabre family heirloom with 36,000 miles
2008 Volkswagen Rabbit 2 door I5-2.5 5spd DD lease
Originally Posted by CamaroSpike23 View Post
she really underestimates the damage i would do to her reproductive organs is the place for all the naughty stuff you can't get away with on this forum...

Last edited by theholycow; 10-23-2008 at 01:27 PM.
theholycow is offline   Reply With Quote