I'd like to add sound deadening material to my car. How adversely will it affect MPG?

[Ecky]

The MPG difference should be minuscule, but you might find that you notice the extra weight in accelerating and braking. My car has weighs less than yours, but I really feel it when I have a passenger.

My vote would be replacing your tires, even if it's only the rears. Not all tires are created equal when it comes to noise transmission, and my (uneducated) guess is that you're not hearing noise being transmitted through panels, but rather, it's coming from the suspension up into the frame. Dampening your floors will probably do little to help.

A quick google search returned this:

DIY solution to deadening tire noise

You might also be interested in this:

Lexus LS Wheels Have Sound-Deadening Hollow Spokes » AutoGuide.com News

[GearHead]

I actually have LRR tires that are pretty new. I'm just under 6k miles on them. I can stand the noise. I'm just a tad concerned about the low MPG I'm currently getting with my VX.

[Ecky]

Might want to start another thread on that.

It could be your driving style - my father-in-law gets low 40's to high 50's when he drives my car, and for the life of me I can't figure out how he does it. On the same trips I average 70+ doing nothing but driving at a constant speed (~the speed limit, even), and have pulled 100+ when I'm actively trying.

It could be a mechanical problem - bad compression? Clogged EGR? Brakes rubbing? Tires out of alignment?

It could simply be your driving conditions. Even the best drivers will get horrible economy in stop and go traffic, because any time you need to use your brakes, you're very effectively converting gasoline into brake dust. Compound that with the engine idling while you're not moving, and you're got a recipe for poor fuel economy.

[GearHead]

I'll start another thread .

[GearHead]

Update:

I've been consistently getting 40 MPG all day every day pretty much. I've been pretty happy.

I added sound deadening material to the floors and realize that when it was done, the entire floor was covered. I did the math and I can save about 30 lbs if I remove 75% of it. Is it worth the aggravation of removing the carpet to save 30 lbs?

[Daox]

That going to be a personal preference, but I would say no. 30 lbs is not going to be noticed at all.

[mcrews]

Originally Posted by GearHead

Update:

I did the math and I can save about 30 lbs if I remove 75% of it. Is it worth the aggravation of removing the carpet to save 30 lbs?

you would be better off dropping 15 lbs yourself!

Of course, I don't know you, and you could be skinny as a rail!

BUT. ..most of us could lose 15-30lbs before starting to worry about 30lbs of material on a car.

[GearHead]

Originally Posted by mcrews

you would be better off dropping 15 lbs yourself!

Of course, I don't know you, and you could be skinny as a rail!

BUT. ..most of us could lose 15-30lbs before starting to worry about 30lbs of material on a car.

I am a tad on the skinnier side. So, I must account for something :-D.

Originally Posted by Daox

That going to be a personal preference, but I would say no. 30 lbs is not going to be noticed at all.

Okay, I appreciate that. I wish I knew how much my car weighs now with all the sound deadening material I added, but I think it can't be more than say 80-100 lbs.

The last thing I can do to my car is to clean the injectors and I've done everything I can do mechanically to boost the MPG.

[NoD~]

Depends. 30lbs on a 1500lb car is a lot of weight (2%)! But 30lbs on a 4000lb car is very little (0.75%). This is especially true for your 0-60 times (or just daily driving acceleration).

For MPG sake, it depends on your routes and how you drive. The more you use your brakes, the more weight effects you. Hence, why weight makes little/no difference on the highway. But, the above applies and you really need to look at it in percentages.

Could you tell a good difference in sound when you added it? I'm guessing it was subtle difference. That's been my experience, at least, mostly dulling the noise, but not ridding of it (a lot of drone/low-mid frequency still about as loud). As mentioned in a prior post, 2-leaf system using foam and MLV is far more effective, but also, adds a lot of weight.

[GearHead]

I can't say if it improved the acoustics in the car because my car still isn't completely put back together.

I don't have speakers or door panels in the car right now.

I have to make this decision within the next week if I want to remove some of the material. The rest of the dash is going back in.

Something is just bothering me about having too much sound deadening coverage on the floor.. Only 25% should have been covered, but the installer put down 100% coverage. It's been on my mind for a while now.

I'm trying to get the best MPG out of my car. I just can't see 40 MPG city mixed with highway is the best I can get...