How much does exhaust (mufflers, etc.) affect gas mileage?

[mongo]

o2 sensor

i got a mustang same thing

it was the o2 the computer thinks the trucks running bad so it turns up the fuel

 

[Sidewalk]

cat converters do fail...but not as often as people like to think they do.

I think they get stolen more often then fail

filling up at a different station? they might be rippin you off and youre not getting as much gas as they say.
Its happened before.

I would doubt that. The fines are not near worth the hassle of screwing with the pumps.

i wouldn't hardly call 3 MPG a 'substancial' loss in fuel economy. When mine was plugged i think i burned through 5 gallons in about 60 miles.

15% is pretty substantial. People claim to feel 1% performance increase, I am sure you would feel a 15% decrease.

it was the o2 the computer thinks the trucks running bad so it turns up the fuel

It should throw a code. Usually an old sensor wil just react slowly, not read low.

 

[Bryan22]

closer to 10% on a 2.3 and a plugged exhaust system would display more effects than just a 3mpg decrease in most cases. secondly, it's not performance hes complaining about, it's fuel economy. you don't 'feel' a loss in fuel economy, you notice it when you go to fill up.

 

[Sidewalk]

closer to 10% on a 2.3 and a plugged exhaust system would display more effects than just a 3mpg decrease in most cases. secondly, it's not performance hes complaining about, it's fuel economy. you don't 'feel' a loss in fuel economy, you notice it when you go to fill up.

3/21=14.2%, so I say closer to 15% then 10. But maybe I don't know math anymore.

Fuel mileage is connected to performance. A noticable gain or loss in either will affect the other. Sure, I do not notice a change in performance when I go from 25 to 30 MPG in my wife's PT Cruiser, but that is because I changed my driving habit to setting the cruise control to 55 instead of 65.

 

[DailyDriver]

What about the whole "winterized" gas formula that was mentioned???

I made it to work today without my new muffler falling off . Got to fill up today. Should be able to tell in a couple of days if the muffler makes a difference.

When I took the old one off, it was full of small rusted out holes & it sounded like there was a mix of sand & marbles in there lol. I shined a light in the pipe & looked at the back end of the cat, all I could see was what appeared to be a wire screen.....didn't tell me a whole lot.

 

[DailyDriver]

It should throw a code. Usually an old sensor wil just react slowly, not read low.[/QUOTE]

No codes, however the O2's have never been changed.

 

[Bryan22]

3/21=14.2%, so I say closer to 15% then 10. But maybe I don't know math anymore.

Fuel mileage is connected to performance. A noticable gain or loss in either will affect the other. Sure, I do not notice a change in performance when I go from 25 to 30 MPG in my wife's PT Cruiser, but that is because I changed my driving habit to setting the cruise control to 55 instead of 65.

average MPG for a 2.3 is closer to 25. And i could drop in a 4.0 lose 10 MGP and gain 100hp. Gas milage and power are NOT dirrectly related. that's a dumb assumption, especially since the way you put it is that; power goes up as fuel economy goes up. if that was the case everyones car would have 1000hp at 100MPG.... Like i said the OP did NOT complain about a loss of power, rather a loss of fuel economy. I'd say it either needs a good tune up or the winter blend of gas is messing with mileage.

 

[DailyDriver]

I've gone through another tank of gas & the mileage didn't really improve with the muffler change. I'm not saying the "winter blend" isn't the cause, but I've never had this problem in the 9 years of owning this truck. Besides, I'm not sure if we get the winter blend in the New Orleans area.

Again, plugs & wires only have 17,000 miles on them & they look fine.

This bites!

 

[Wicked_Sludge]

check tire pressure, check for dragging brakes, sheck for a bad cooling fan clutch. how old are your 02 sensors?

 

[DailyDriver]

Tire pressure is 35lbs. O2's are 9 years old, but I thought they throw a code when they go bad? Brakes & fan clutch will have to wait until the weekend.

 

[Sidewalk]

O2's won't always throw a code, but usually will. Usually they don't completely fail, they just start to respond slowly.

Fan clutch is easy, just grab the fan (engine off of course) and see if it will move by hand (there will be some resistance).

 

[DailyDriver]

So if the fan clutch moves by hand with a little resistance it's good to go?

Just curious, how would this affect the mileage???

 

[Wicked_Sludge]

a cold clutch will resist spinning at first, but should free up and spin relativly easy (as sidewalk said, there will be some resistance).

a seized fan clutch will be spinning the fan at full speed all the time. this puts excess drag on the engine, costing you fuel mileage and power. its about the only way fan clutches ever fail.

 

[Bryan22]

I had a seized fan clutch and couldn't tell by oving it by hand. The real giveway a fan clutch is bad, is when you can hear it whirring constanly. A good fan clutch will spin at first start up and should get noticably quieter withing 20 seconds of starting. If the whirring continues after starting and dosen't go away, it's pretty much safe to say it needs to be replaced.

 

[DailyDriver]

Thanks for all the info.