How much gas would a 200lb reduction in curb weight save?

[Submariner]

Let's say you have a typical 200lb car and you were to shave 200lbs off it's weight (without affecting running gear, tires, etc)  Is there any way to roughly calculate the gas it would save?

[FlatBlackCaddy]

I thought that once at speed, fuel mileage was largely due to drag coefficient, rolling resistance and mechanics(gearing, thermal efficiency?). If that is the case, then it really shouldn't change much if at all. Maybe a little bit because it would be less mass to get moving from a stop.

[Submariner]

I thought that once at speed, fuel mileage was largely due to drag coefficient, rolling resistance and mechanics(gearing, thermal efficiency?). If that is the case, then it really shouldn't change much if at all. Maybe a little bit because it would be less mass to get moving from a stop.

Let's say we are talking about a city car...maybe something like a Smart or a 500 that is doing a great deal of stop and go driving. 

[FoMoJo]

Let's say you have a typical 200lb car and you were to shave 200lbs off it's weight (without affecting running gear, tires, etc)  Is there any way to roughly calculate the gas it would save?

It would be easy to test if you put a 200 lb. dumbbell in your car a drove around with it and then did the same driving without it.

[MX793]

Highway mileage would be largely unaffected, but city mileage would improve because it now takes less energy to accelerate the car, and you therefore use less fuel in stop-and-go.  How much?  Too many factors to pin it down quantitatively.

[Rupert]

Pretty sure that if you have a 200 lb car and you shave off 200 lbs, you'd be sitting on the ground making engine noises and shifting with a stick you find under a tree.

[MexicoCityM3]

Pretty sure that if you have a 200 lb car and you shave off 200 lbs, you'd be sitting on the ground making engine noises and shifting with a stick you find under a tree.

Beat me to it. It would save all gas.

[hotrodalex]

I think it would have a higher mileage gain in cars with smaller engines. But still only like a 1 mpg difference.

[MexicoCityM3]

It would be easy enough to ADD 200 lbs in the trunk and carry them around in the trunk to measure the impact.

[hotrodalex]

Which is 1-2 passengers. Not much of a difference.

[Rupert]

I used to notice that my Miata handled differently with a full-size passenger in it, and my old old Novarolla was much slower.

[hotrodalex]

Both small cars with small engines, thus my first post.

You don't really notice another passenger or two in a CamCord.

[Rupert]

Aye. You need more than 500 lbs to notice any difference in the Explorer, and probably 1000 lbs to notice a power difference. And it's not a particularly powerful engine.

[12,000 RPM]

I did something like this with the Z. Drove up to NYC with wifey and all her stuff, drove back down solo (she flew back earlier for work). Don't remember any difference in gas mileage.

I think weight has a much bigger effect on dynamics. My 1st Accord was relatively softly sprung and in my youthful ignorance I ran lowering springs with stock shocks. I also had 2 12s and the trunk, which with an amp weighed about 90lbs. I got used to it at first, but eventually I got tired of the subs/weight and took it out. The rear end felt more responsive and the car definitely accelerated faster.

[MX793]

I did something like this with the Z. Drove up to NYC with wifey and all her stuff, drove back down solo (she flew back earlier for work). Don't remember any difference in gas mileage.

I think weight has a much bigger effect on dynamics. My 1st Accord was relatively softly sprung and in my youthful ignorance I ran lowering springs with stock shocks. I also had 2 12s and the trunk, which with an amp weighed about 90lbs. I got used to it at first, but eventually I got tired of the subs/weight and took it out. The rear end felt more responsive and the car definitely accelerated faster.

On a long road trip like that, you likely spent the vast majority of your time cruising relatively steadily on the highway.  In which case, weight doesn't play a significant role.  When accelerating, such as in stop-and-go, weight plays a much larger role in fuel consumption.

[2o6]

I only start really feeling it in the Yaris after more than one passenger.

[AutobahnSHO]

200lb probably wouldn't make a huge difference,

https://www.google.com/?gws_rd=ssl#q=gas+mileage+weight+calculator