Bad Gas Mileage And Thumping-ish Sounds

Daytona · 12-18-2005, 09:57 PM

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 · 12-18-2005, 10:37 PM

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 · 12-19-2005, 09:47 AM

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 · 12-19-2005, 09:52 AM

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 · 12-19-2005, 11:44 AM

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 · 12-19-2005, 06:04 PM

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 · 12-19-2005, 08:52 PM

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

(1month after a seafoam treatment)

12-19-2005, 09:04 PM

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 · 12-20-2005, 12:00 AM

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 · 12-20-2005, 12:39 PM

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 · 12-20-2005, 12:48 PM

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 · 12-20-2005, 12:51 PM

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

PlainOldOlds · 12-20-2005, 01:09 PM

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

Daytona · 12-20-2005, 01:38 PM

Quote:

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 · 12-20-2005, 01:47 PM

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 · 12-20-2005, 01:54 PM

^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 · 12-20-2005, 01:57 PM

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 · 12-20-2005, 01:57 PM

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 · 12-20-2005, 02:14 PM

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 · 12-20-2005, 07:15 PM

Daytona, for the thumping, check my thread. 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.