Bad Gas Mileage And Thumping-ish Sounds

[Daytona]

Due to the high cost of gas I've been driving even more conservatively than usual the past few months. However, these past 2 tankfuls have gone by much quicker than usual. I usually get @ 24 mpg in my mixed driving but lately am only getting @ 20 and that's with more highway driving than usual, too. Same gas as always - Sunoco 87 Octane. And I'm not running the A/C (duh!) or the heater any more than usual either.

Been noticing a thumpy sound, too, coming from the front end. Not a heavy sound. A rolling muted thumpy sound. I used to associate that sound to my tires being underinflated but I got my defective tires and bad valve stems replaced a while ago and the current set up looks fine. Brakes look okay, too. The hubs were fine this summer when the dealer was checking out all of the sounds and making sure that nothing else besides the tires were bad. I don't know if the sound has been there & I'm just noticing it now due to my being more sensitive to trying to figure out what's wrong, or if it just started and might be conected to my sudden drop off in performance.

Anyone got any clue as to what might be causing this sudden decrease in efficiency? No time right now to take it in to be checked by the dealership.

[misslindseysue]

Winter fuel will make a difference, as will just plain cold weather (both negative impact to fuel economy). Gas gets adjusted around Thanksgiving, usually, depending on the weather in your area. Also, when you have the front defrost on, the A/C compressor is on, so you're using just as much power/gas as you would be with the A/C on.

[Daytona]

I've seen a difference in winter fuel vs. summer fuel but this is even more extreme of a difference.

Plus I haven't been using the defrosters that much (fortunately) on this tankful, relative to how much I might on rainy days in warmer weather.

[doubleN0alero]

i'm in the same boat boss...my mpg has been just down right terrible...not sure why they switch gas down here, but whatever.

[cannaert]

Same thing. But then again I have snow evey were and have the heat on like a mad man tryying to stay warm. But yea iwas at 22-25 now i am back down to 19-22 it sucks.

[misslindseysue]

Damn... I figured 26 on my last tank, driving to the proving grounds and back only. It's a 70 mile round trip, probly 15 miles of that aren't on the highway. I get my gas at the truck stop on 94 now, it's 20 cents cheaper than anywhere else around here.
Anyway, I figured that was pretty decent, for it being so damn cold, on winter fuel, and I drive 80 on the highway. If I don't get close to 30mpg come summer I'll be looking into one of those sweet employee lease deals on a Chrysler product. Since they get such great economy. :rolleyes:

[eag182]

I got 27mpg in 35*F weather on the highway (v6)(avg 85mph)(a few days ago).

(1month after a seafoam treatment)

[Lovestheh20]

I've been getting avg 17 w/ 75% hwy. its bad, I need to get my UIM gasket fixed this break. hoping it will get me back some..

[PlainOldOlds]

I went from a 1994 3.0L V6 (Mitsubishi) Dodge to my 2.4L 4 banger '99 Olds, and still use about the same amount of gas! I love the car, don't get me wrong... but it does eat a lot of gas up for a 4 cyl.

I estimate 20-24 mpg in mine depending on how I drive, mostly slow acceleration downtown. I bet it would do better on the highway than my old car did though.

[Daytona]

Folks,

This ISN'T about how much gas mileage YOU're all getting. This post is about MY CAR and the PROBLEMS I have with it right now so please stay on topic and only post if you have some input into why I'm hearing the rolling thumping noise and my gas mileage has tanked.

Normally I can get around 210 miles by the time I hit the 1/4-remaining mark on my fuel gauge but lately I'd be lucky to reach 170 miles by that point.

And the noise seems to be worse when the car is cold. I don't seem to hear it as distinctly after I've been driving for a while.

[eag182]

If you think this a bad noise is bad enough to affect the efficiency of the vehicle you should really get it checked out by a mechanic.

[Daytona]

I plan on going next week when I have off from work. Too busy last week and this.

[PlainOldOlds]

Yeah, seeing as you're going to get mad... just go get pro help.

[Daytona]

Originally posted by PlainOldOlds@Dec 20 2005, 01:09 PM
Yeah, seeing as you're going to get mad... just go get pro help.
Quoted post


Oh, like you were a BIG help in this thread. :rolleyes:

[jackal2000]

is the thumpy sound all the time or just sometimes? im thinking its just suspension components. i know my car rides "louder" during the winter because of the cold and all.

[Daytona]

^It seems loudest when the car is cold. I don't hear it as distinctly when it's warmed up. The car is 100% stock so at least I have the added benefit of knowing I didn't screw anything up by installing it incorrectly. I can hear the noise and feel it in the car but it doesn't vibrate the steering wheel like a flat or loose tire would.

Could the suspension components be going bad or is it just natural for them to be making the excessive noise in the winter months?

[doubleN0alero]

i've noticed a bunch of extra noise in the winter time as well mitch. I would assume your added noise is amplified by the fact that its cold. Think about it this way. When you wake up in the morning and its cold in the house, do you really feel like moving? And when you do move, how quickly do you move? Rather in the summer and you wake up and its warm in your place...it just seems alot easier to get moving. Same thing goes. I've noticed that when I first drive my car in the morning it feels like i'm dragging about 10,000 lbs behind me...but then she gets to going.. Kind of the same concept.
I would let it ride until it gets warm outside and then see where the noise goes. If it goes away, then you know its just a winter issue.

[jackal2000]

the way i rationalize it to myself is that since its cold, the parts arent expanding as much so the fit is "loose", hence a thump or dull rattle like i hear. i experienced this last winter as well and this past spring the noise went away when the temps warmed up. granted i hear mine mostly when hitting bumbs, no matter the size, not when driving on smooth surface. i would not jump to the conclusion that your suspension is bad. as far as the gas mileage goes, i dunno man.

[Daytona]

Thanks, guys. Let's hope the cold air is the only real issue and the bad mileage is due to the crappy oxygenated winter fuel (though I've never experienced mileage this consistently bad in the car in previous winters).

[AlbinoMonkeyRat]

Daytona, for the thumping, check my thread (http://invision.aleromod.com/index.php?showtopic=15968). does it have the same symptoms? I wanna know what my problem is too. if you figure out the answer for sure, I'd know too.

[Daytona]

^Funny. I just read your thread before seeing you post here about it.

It's very similar to your issue, however I hear it more when the car is colder than warmer and I can't hear it as well at higher speeds. It's a rotating sound which is why I can hear it better at slower speeds. I, too, thought about maybe one of the wheels' lugs being loose but haven't had a chance to check that out yet. Will have to experiment with braking and see if it does anything to the sound like with yours. Will let you know.

[Neonguy95]

How many miles do you have on it?

I have been wondering latley on mine 01 with 48k, gas mileage bounces around 25-28 mpg mixed hwy and city. What I have been wondering is maybe the 100k plugs aren't doing well with age. It baffles me that Neons (yes my other car used to a be Neon and I still work on them) burn through plugs about 15k-20k how can an Alero or for that matter any other car not burn up plugs in under a 100k.

In mine when the fuel mpg dipped below 25 mpg I cleaned the air filter(K&N) and cut holes in the airbox to allow more air to enter. Yes it is from the engine bay, but with the airflow you get in the engine bay at highway speeds how warm can this air be. ( I could get into a whole 'nother conversation about that) I also replaced the fuel filter and ran Seafoam through it. Gas mileage jumped back up and has been good ever since. This was about 20k ago.

So in short. When was the last time you check your plugs, fuel filter and air cleaner? Air pressure in your tires could also cause a problem and with the cooler air you might check and see if you are underflated.

As far as the clunking or knocking sound can you hear it more with the window down? Have you tried driving Ace Ventura style or in the passenger side and see if you can narrow that down? You may get strange looks, but if you can keep from paying someone to fix it, it maybe worth the embarassment.

Just my opinions.

[Daytona]

Car's got 41K miles on it. I bring it in for every recommended servicing per the owner's manual. My plug wires had to be replaced a few months ago, otherwise no unusual wear internally. Front tires are only 6-8 months old and are holding their air fine.

Noise is more noticeable with the windows closed though haven't tried driving with my head out the window.

[BlackJack]

check the rotors / drums for warpage, and check the wheel bearings. Jack the car up, put it in neutral (key off) and manually rotate the wheels one by one. If you hear a "dragging" or light grinding noise only at certain locations throughout rotating the wheel, then there's your likely culprit. Either one will make your gas mileage go down, and cause a grinding or thumping noise when driving.

Even if your tires are balanced correctly, it will still feel like something is out-of-round.

Also, check the amount of "play" in the wheels by grabbing the tires at positions 9 o'clock and 3 o'clock and jiggle the wheel. If you have an unreasonable amount of movement (light clunking), then higher likelyhood to the wheel bearings being bad or center nut needing to be retightened (check required torque values).

Thirdly, check to make sure all your inner CV's are tight.

[Daytona]

^Thanks for the advice. The dealership culdn't find anything "wrong" with the car that would explain the noise or the drop in mileage but did tell me that my brakes are now borderline and need to be replaced at or before my next oil change. That'll be my 3rd set of front brakes on a car with barely over 41K miles and I don't race the car! Plus they said that my rotors need to be recut and if they can't do that satisfactorally they'll need to be replaced. If my rotors are a little warped, that'll explain the uneven braking sound and maybe the rolling noise. Replacing them would solve that - no? All total I am now looking at over $400 in repairs. Merry F---ing Christmas to me. :pissed:

[brsexton]

Originally posted by Daytona@Dec 31 2005, 09:04 AM
^Thanks for the advice. The dealership culdn't find anything "wrong" with the car that would explain the noise or the drop in mileage but did tell me that my brakes are now borderline and need to be replaced at or before my next oil change. That'll be my 3rd set of front brakes on a car with barely over 41K miles and I don't race the car! Plus they said that my rotors need to be recut and if they can't do that satisfactorally they'll need to be replaced. If my rotors are a little warped, that'll explain the uneven braking sound and maybe the rolling noise. Replacing them would solve that - no? All total I am now looking at over $400 in repairs. Merry F---ing Christmas to me. :pissed:
Quoted post


If I were you I would not pay the dealer that kind of money to use the same subpar GM parts. GM brakes suck and wear fast. I have 46k miles on my 03 and have been through 2 sets of OEM brakes and rotors. The last time, I bought Napa rotors and Akebono pads. I have had them for well over a year and several thousand miles and no sign of wear.

[Daytona]

^Something to keep in mind for next time.