Fuel Economy!

[XJay]

My fuel economy on my '99 has progressively gotten worse over the last two years, and I've seen a change (for the worse) in the last three weeks. Next weekend, I'm changing the air filter along with Seafoaming the upper end of the engine - would it be helpful to run some through the gas tank/fuel system as well? I'll also be changing the fuel filter, plugs, and wires come February.

My questions are simply, what could be killing my fuel economy, and what else can I do to improve it?

Also, my engine stumbles a bit between 1100 and 1400 RPM, could this play into the problem with the fuel?

One more -will a coldair induction kit improve or worsen fuel economy?

Thanks in advance...

 

[Adverse2Change]

You're taking the proper steps to improve it. A drop in K&N will help a small bit with MPG, as will a CAI. Are you also keeping up with your tire inflation and wear?

 

[02ponypackage]

Check tires, maybe a better intake CAI with K&N or any good filter, fuel filter change, along with ne other needed filter changes

 

[XJay]

I've changed the air filter, fuel filter, and plugs/wires. I've Sea-Foamed the fuel system (via the gas tank) and the cylinders (via the intake vacuum hose). Tires are correct size and inflation.

Still, fuel economy is getting *ridiculously* worse. What else is there to do?????

 

[ChingonStang]

It's probably the gas. This ethanol mix is crap.

 

[232Mustang95]

It's probably the gas. This ethanol mix is crap.

 

[ChingonStang]

 

[V6muscle00]

im with chingon.. the ethanol mix sucks
but more importantly we def need more wookie and maybe some cowbell too

 

[raz54]

You can never have too much cowbell......


Have you had the cats checked to see if any are plugged?

 

[XJay]

I read in another fuel economy thread where someone suggested making sure that the Overdrive is still on.

What is 'Overdrive', and how does it affect fuel economy? I'm assuming that since the light on the dash comes on when it's off, that Overdrive is meant to usually be on?

I know where the overdrive button on my automatic stick shift is, but when I press it, nothing happens (no light on the dash) - what does this mean, and could it be affecting my fuel economy?

 

[XJay]

Help?

 

[232Mustang95]

The bulb might be busted and yes that will hurt your milage if it's off.

 

[ChingonStang]

The bulb might be busted and yes that will hurt your milage if it's off.

 

[Give Me TP]

OD is on by default every time you start the car, so it is unlikely that OD being off is the source of the problem. To comfirm though, find out what the rpm is at a given speed and compare that to what others on here experience with similarly equipped 99 models.

Also +2 on need more kowbell

 

[TheCrazy1]

The rpm should be around 2200 or so at 70mph. At least somewhere in the low 2000 range. If it's way higher, then overdrive has left the vehicle! Sounds like you've done everything there is to do as far as basics to improve the mileage. What exactly is it getting per gallon? My g/f has a 2001v6 with manual trans and she averages about 23 to 24mpg. On a road trip, it'll do around 30! You say it stumbles a bit too... it might be worth your while to replace the coil pack... they seem to go out and cause misfiring, stumbling, etc.... How many miles are on your car?

 

[XJay]

I've around 135,000 miles on my car. I'm wondering if I need to replace the fuel injectors......am I getting ethanol at the pump now?

 

[AP1995V6]

I usually get around 300 miles before I fill up - in the neighborhood of 1/4 tank.

Is your CEL on? Running rich will definitely cause your gas mileage to crap out. Driving habits affect mileage alot. I dogged my car one tank and got around 18mpg. "Normal" driving got me around 22. And Casual driving got me 24. Most of my driving is on interstate or city driving so I never see anything over 25.

Another thing you could do is to pop out the spark plugs and check their appearance. Make sure they're gapped correctly and such. Check brake pads for wear. A siezed brake caliper will make your gas mileage drop as well. Check the emergency brake to make sure it isn't sticking.

 

[XJay]

I usually get around 300 miles before I fill up - in the neighborhood of 1/4 tank.

Is your CEL on? Running rich will definitely cause your gas mileage to crap out.

Forgive me, what is a CEL?

 

[232Mustang95]

CEL = Check Engine Light

 

[jefferz]

Forgive me, what is a CEL?

I think on the 99-04s they will say Service Engine Soon instead of Check Engine...just so you know. I just cant remember off the top of my head cause mines never been on in my 02 GT