I'm curious to see if anyone is knowledgeable in this area. I know that the lighter the vehicle then the better gas mileage it will yield. However, how much of a difference does weight make? If my car was to weigh 2800lbs and averaged around 25mpg, then what gains in mpg am I to expect if I reduce weight by 100lbs, 200lbs, 300lbs, etc? anyone know?

 

Depend on usage... or how you drive the car.

Weight contributes to rolling resistance drag. Lighter the car, less rolling resistence of course. The faster you go, the bigger the rolling resistance too and the relationship between speed and rolling resistence is linear.

Another thing weight matters would be the inertia... naturally the heavier it is, the harder it'll be to accelerate it.

So if you're usually cruising on the highway, weight isn't all that important.

Aero drag plays a much bigger roll when you speed up. Aero drag also goes up significantly as speed increases... rolling resistance drag will end up being rather insignificant at hwy speeds. Things that cause the most aero drag are the wheels.

This is why SUV mileage is a lot worse than vans even cruising on highways. Both may weigh about the same, but vans are far more aerodynamic than suvs because vans have smaller wheels and they are not as exposed to the air.

When driving in the city's stop and go traffic, mileage of comparable size suvs and vans will probably be about the same.

For a 2800 lb car, I doubt you'll be able to see significant increase in MPG even with 300 lbs of weight savings. However, for sure it will improve you acceleration and track time by a few seconds... considering one lap will probably take you 2 minuntes on an average race track? Couple of seconds out of 120 seconds is a very small percentage, but when you're racing, obviously every single ounce of weight savings counts..., you will probably save about similar percentages in fuel, but can you really see the difference in 1% savings in fuel?

Bottomline, please don't gut your car to save fuel. It'd make sense on the track, but makes little sense on the streets.

 

Thnkx for the response. I must admit I am not expecting great increases through reducing weight, and have no intentions of gutting my car at all.

I know weight plays a huge roll in bottom end acceleration as little up top compared to the cars aerodynamics, but I recently read an article where a car was getting 100mpg!
The main focus of the makers was the weight of the vehicle which is what they stressed the most in the article. While the car had a hybrid motor(sorry I do not recall from what vehicle) they focused on creating a light weight vehicle overall. according to the article weight is the key factor in fuel economy. They also went on to sate that almost all auto companies can have there cars ranging near that 100mpg area if they would use light weight materials(carbon, etc.), but is something that will never happen due to the costs involved.

Myself I am stuck in LA where I see a lot more bumper to bumper then I do normal highway cruising(especially on my routes). I know the biggest benefits come from going with light weight wheels which will improve acceleration as well as the initial inertia. aside from that I was curious to see if studies were done to detemine gains in mpg through vehicle weight reduction under identical driving conditions.

For example my S was getting around 200 -210 average on a fuel tank with normal driving when was stock. after adding Intake/Header/Test pipe/Exhaust/flywheel my S began to get around 240-250 on a full tank with the same driving. Now was this due to the fact that my car was making more power, or because of the reduction in weight due to the lighter parts? I think it was a combination of both, but am curious as to what made the biggest difference.

 

Its not the extra power its that the engine is less restricted making it more efficent, thus giving you better milage.

Now to say that you added ~50 more miles just because of the mods is probably unlikly. I'd say driving habit might come into play as well.

Its very hard to say "I drove exactly how I did on my last fillup." Statisticly that means nothing as you could imagine

Unless you in a controlled enviroment, the driving will always be different.

So to answer the question, yes I am sure it helped but I don't think THAT much