POOR Gas Mileage

[2OOOLS]

Hello People,

I have heard a lot of stories here and there that gas mileage for Grand Marquis in town average is 17 to 18 MPG.

The fuel economy of my 2000 MERCURY Grand Marquis LS is 12.55 mpg in the city!

I am confused
Do you think its normal? If not, whats wrong? Any suggestions?

TIA
2OOOLS

[fredjacksonsan]

If you have a heavy foot, it's certainly possible. What do you get on the highway @ 55-65?

[2OOOLS]

Originally Posted by fredjacksonsan

If you have a heavy foot, it's certainly possible. What do you get on the highway @ 55-65?

Thanks a lot for reply!

I dont see big difference on the highway. Maybe extra couple MPG.

But what do you mean by "heavy foot"? I am trying to be as gentle as possible. Do you think it may cause such poor gas mileage?

TIA
2OOOLS

[fredjacksonsan]

"Heavy Foot": giving a lot of gas to start off, etc.

If you're consistently getting poor mileage, I'd start with the O2, or oxygen sensor. I've seen several posts where poor gas mileage was caused by a bad oxygen sensor. The easy "backyard mechanic" way to check, is to have a look/feel at your tailpipe. Is it black, shiny and wet inside after driving? It may also smell a little like gas. If so, then your car is running too rich and the extra gas isn't being burned, but being put out the tailpipe.

Also, how many miles do you have, and do you have good plug wires and spark plugs? Those can reduce mileage also.

Check your tire inflation, too. If they're off they can contribute to lower mileage.

[2OOOLS]

Originally Posted by fredjacksonsan

"Heavy Foot": giving a lot of gas to start off, etc.

If you're consistently getting poor mileage, I'd start with the O2, or oxygen sensor. I've seen several posts where poor gas mileage was caused by a bad oxygen sensor. The easy "backyard mechanic" way to check, is to have a look/feel at your tailpipe. Is it black, shiny and wet inside after driving? It may also smell a little like gas. If so, then your car is running too rich and the extra gas isn't being burned, but being put out the tailpipe.

Also, how many miles do you have, and do you have good plug wires and spark plugs? Those can reduce mileage also.

Check your tire inflation, too. If they're off they can contribute to lower mileage.

thanks again fredjacksonsan,

Thats exactly what my mechanic first guess was. Sensors.
He also recommended to take Computer Diagnostic. Will it be able to find a problem in my case?

I got it about "smell a little like gas". But when is it something wrong... if my tailpipe is black, shiny and wet or not inside after driving?

Right now I have couple miles over 48549.3. I gased up yesterday. Since last time I filled it up I drove 167.3 miles. So:

167.3 miles / 13.327 gallons = 12.553 MPG

Tire inflation is Ok too. According to label on rear right door opening its gotta be 32 PSI for this kind of tires.

Plug wires and spark plugs I did not check yet

TIA
2OOOLS

[fredjacksonsan]

The computer diagnostic will likely tell you which sensors aren't working properly. Though expensive, it might be worth it.

Hold on a second.....48549 miles? Aren't you still under the Ford 5/50 warranty? If so, it should be a free diagnostic check.

[2OOOLS]

Originally Posted by fredjacksonsan

The computer diagnostic will likely tell you which sensors aren't working properly. Though expensive, it might be worth it.

Hold on a second.....48549 miles? Aren't you still under the Ford 5/50 warranty? If so, it should be a free diagnostic check.

To be honest I am not sure about that.

How can I found out? I bought the car from non-Ford dealer on eBay. As long as they said the car was sold AS IS. Or it has nothing to do with what you called Ford 5/50 warranty and I can get it anyway?

TIA
2OOOLS

[fredjacksonsan]

I would find out if Ford has a phone number to call about warranties, and call to find out if yours is still in effect or not. If it is not, then you are no worse off than you are now. If so, then

[2OOOLS]

Originally Posted by fredjacksonsan

I would find out if Ford has a phone number to call about warranties, and call to find out if yours is still in effect or not. If it is not, then you are no worse off than you are now. If so, then

Unfortunately, after taking all my info, including my cell phone number ppl at Ford told me that I had 3/36 warranty and it was expired...

...but thats ok I did not count on them anyway

[fredjacksonsan]

OK so now we're down to paying for the diagnostic to find out what is wrong. I'd bet on a sensor.

[cobradude360]

on my 92 i get 13.5 city when ive got a case of the lead foot and 15 when im just driveing normal so im right with ya with the bad milage but thats the price u pay for a nice v8 i guess

[jimmytroanoke]

Originally Posted by cobradude360

on my 92 i get 13.5 city when ive got a case of the lead foot and 15 when im just driveing normal so im right with ya with the bad milage but thats the price u pay for a nice v8 i guess

On my 95 I get 19 city and 27 on the hwy. 3 out of 4 O2 sensors are original with 140k on the clock. Get a proper diagnostic done, don't just fire up the parts gun! There are a lot of things that will make you run rich, not just O2 sensors.

[SiZzOuRcE]

I got a 94 and was getting 12-13mpg around town, I dont drive on the hwy much so I don't know what the hwy mpg is. But as soon as I threw in some AutoLite double plat plugs and some warner cables, my gas milage shot up to 15.5-16 around town. And around 19 on the hwy.

I also threw one of those tornadoe fuelsaver things in and it increased the cooling and performance noticibly but kept the mpg the same.

Alot of time also the EGR valve will be the cause of bad gas milage, I know thats why Im getting such poor milage on my car, but Im not going to get it fixed cause I just don't want to pay to get it installed.

Also try buying a K&N air filter, it might be your air intake. My car smokes oil like a bitch tho, I can't figure out why, but Ill find out as soon as I get a check up. I only have 50k mi on my car, so that should tell you something about these types of cars.

[Sparkey56]

Go by your local AutoZone store and get them for FREE to scan your car as long as it 96 and up. Copy down all the codes and then have them look it up in the computer. I used to work for one up in Mass.

[2OOOLS]

Originally Posted by Sparkey56

Go by your local AutoZone store and get them for FREE to scan your car as long as it 96 and up. Copy down all the codes and then have them look it up in the computer. I used to work for one up in Mass.

thanks Sparkey,
I will definitely do that... if they do that in my area!

I went to local mechanic btw and he told me that unless check engine light is ON the computer diagnostic could be pointless because it will not probably find any problem. Is that true?

However,even with check engine light OFF, it may find a problem only if there was problem before and it was not fixed, but deleted (reseted).

Also, we looked under the hood and he told me that I have original spark plugs and wiring, and what I have probably nothing to worry about.

At same time he asked me if I am noticing anything unusual when I accelerate and I said NO, but I do have strange feeling like my "trany sleeps" or like its "loosing a power" somewhere at the start. So I assume there is something wrong with the TUNE UP.

TIA
2OOOLS

PS.I asked one of my collegues, who has similar car but GS, and told him about my problem and he said that my gas mileage is way too bad and he is getting in average 18-19 in the city.