That may well be the first time I've ever seen hard data from an actual experiment. Bang up job!

This pretty much confirms what I've been saying all along -- you need a significant perecentage of weight difference to make a measurable FE difference. Taking 50 pounds out of a 3000 pound vehicle will simply not yield a worthwhile increase (unless that 50 pounds was just wasted space).

So, if you have a 2,300 pound Civic, and you think you can yank out two hundred pounds (more than you'll get from removing the backseat, trim, spare tire, and buying wheels)...go ahead. It might be easier to just drive around with never more than half a tank of gas, which weighs ~6 pounds per gallon.

Can anyone else provide hard data for different types of vehicles? The effect may differ in vehicles with different power-to-weigh ratios, for example, or different MPG-to-weight ratio...

see earlier posts about 5 people in a Grand Prix going over mountainous roads at 55-75mph. 3300lb base, 155lb avg. each person. approx. 200lbs baggage. 380 miles, 34mpg.
With just me and the wife (-3 people) It was 34.88mpg.

so, approx 4275lb in my car net me 34mpg.
3600lbs net 34.88mpg.

Same speeds, same techniques, same distance, same time point to point (almost exactly, off by a couple minutes).

So, where is my car's most efficient power/weight? seems its a pretty broad range for highway cruising.

That's a mere 2.5% change in MPG (seems to be within a reasonable margin of error) for a whopping 19% change in weight. :( That surprises even me.

I know this sounds like approximately the same thing, but I'd really like to see the difference when a car designed to weigh X pounds has its weight reduced to X-Y pounds, rather than when its weight is increased to X+Z pounds. That's much more difficult to test, since significant weight reduction is so difficult.

the problem with an experiment like you described is the money associated with it.

you said before (and I agree whole heartedly) taking out the seats and the spare isn't really that much weight. the only way to do the experiment that you describe is to start replacing body panels with fiberglass or carbon fiber.

I also would like to see the results of a test like that. I once priced a carbon fiber hood for my truck (to make it faster and look cool) to the tune of around 2K. maybe it was where I was getting it from, maybe that is typical, I don't know.

Wow.....really an insignificant difference 675lb makes. Not worth the hastle of taking any necessary items out then.

When I someday get my protege running, I'll put the stock weight back in, probably with some dead weight. I'll run it for a while to get a baseline. I'll then remove the weight to its current stripped out set, and run it again. That'll give me an idea if removing the 300lbs made a FE difference, or just a handling difference.

btw, I have to add the weight back in for the baselines since it has a new motor and different tranny than it did before, so past numbers are meaningless now. It may be a while......

i think the two different experiments show that its different for every car and some cars will significantly lose mpg with added weight, where others may not even flinch. the same is true for removing weight.

when i had my d16z6 in my 94 civic hatchback i was getting mpg that a normal 94 si would never get. granted my hatchback weighed over 300lbs less than the si model of that year.

When I had my metro I stripped about 120lbs off of it and noticed a major difference. That is just MY car, so I can't vouch for others, but 120lbs on an already light car made a difference. Since the car was underpowered on hills, it had an easier time going up them. Actually, that much weight was enough to completely change my shifting pattern. On a hill near my gf's I had to make it scream in 2nd becuase it was so steep and it would dog down in 3rd. After I changed it, I could easily scoot up the hill in 3rd with low rpms.. I would drive up my street in 3rd with moderate rpms. After the weight loss, I drove in low 4rth.

I definitly noticed a gain in mpg AND overall speed, so noone can tell me it doesn't work:D

[QUOTE=thisisntjared;121325]i think the two different experiments show that its different for every car and some cars will significantly lose mpg with added weight, where others may not even flinch. the same is true for removing weight.
QUOTE]

My dad's H2 Hummer didn't budge at all when we towed at 18' speedboat to FL from MD...

Perhaps the pattern is that vehicles with power to spare (like that Grand Prix) won't show a measurable difference, but underpowered vehicles like that Metro that could barely get up the hill will show a difference proportional to the precent of weight removed.