Bad gas mileage?

[Silence*]

So last week I didn't have a car, so I borrowed my mom's 2002 XLS (4.0L SOHC). I put about 110Km's on it in the day I had it, driving across town 2 - 3 times. It had a full tank when I got it, and when I got home the gauge only read 1/8 of a tank used.

Over the weekend I picked up a '02 Sport with the same engine and it has almost the same mileage of 130,ooo Km's (around 80K miles). I've put 110km's on it in the past 2 days and Iv'e used over a quater of a tank! Mind you it has been alot colder now then last week and I've had the heat on more, but other then that I don't see how it can be so different?

What could be causing this? Bad Air Filter? o2 sensors? Sure my driving style could contribute a little, but I drove my mom's harder then I have mine so far...

 

[shadowless127]

change fuel filter and get a new air filter.

 

[aldive]

Your method of determining gas mileage in extremely inaccurate.

Gas mileage is determined by dividing miles traveled by gallons of gas consumed.

 

[zonianbrat]

Your method of determining gas mileage in extremely inaccurate.

Gas mileage is determined by dividing miles traveled by gallons of gas consumed.

X2 I was going to say the same thing. You can not get a good feel for you mileage on 110km or a quarter of a tank. Listen to Aldive he seems to be the mpg master!

 

[shadowless127]

^^ I didn't think I had to point that out...

Also, the full size X has a slightly bigger fuel tank (1-1.5 gals bigger iirc)

 

[huntersteve61]

still theres a very noticeable difference.. I feel much more then 1-2 mpg.. I'd check o2 vacuum leaks and filters.. good tune up too bro... if it wasn't that drastic I'd say just maintenance sounds like you got a small problem needs attention

 

[tripplec]

Filter

change fuel filter and get a new air filter.

Fuel filter has nothing to do with gas millage, air filter yes. If the fuel filter is plug, poor performance and bogging down or power dying under load and heavy peddle pressure. This is no different than any other vehicle or engines symptoms.

 

[X~FACTOR]

You gotta go through a couple of tankful to get an accurate MPG.

 

[aldive]

Fuel filter has nothing to do with gas millage,

Sorry, but that statement is inaccurate.

 

[Silence*]

Oh I know its an inacurate way of telling, it just seems like its sucking back more gas then It should be. I'm writing down how many Km's I get per tank and I'll check back with those results in a few weeks. I just want to get some advice now so I can budget repairs and what-not.

 

[huntersteve61]

how do the wires look? have you ever done plugs and wires??? air filter? how about your 02 sensors?? you'd be suprised to see that owners who don't do this.... loose a little bit here and there....

As for the fuel filter.. I understand loss in perf, bogging down, possible burning up the pump but if you've lost all this how can you say you haven't lost some mileage?? I doubt this is the only problem.. but I'd tell ya check over everything

 

[Silence*]

I just got this truck and haven't done much work to it. Im getting the same mileage constantly, 265Km's on 55L of gas (= 165 miles on 14.5 gallons I think?). I'm thinking plugs and o2 sensor are culprits, along with a most likely clogged air filter. Maybe a good seafoaming will help too?

 

[shadowless127]

Fuel filter has nothing to do with gas millage, air filter yes. If the fuel filter is plug, poor performance and bogging down or power dying under load and heavy peddle pressure. This is no different than any other vehicle or engines symptoms.

if any filter is clogged it's going to take more work and more of whatever is passing through the filter to get the same job done compared to a clear path... this is common sense...

 

[JDraper]

So last week I didn't have a car, so I borrowed my mom's 2002 XLS (4.0L SOHC). I put about 110Km's on it in the day I had it, driving across town 2 - 3 times. It had a full tank when I got it, and when I got home the gauge only read 1/8 of a tank used.

Over the weekend I picked up a '02 Sport with the same engine and it has almost the same mileage of 130,ooo Km's (around 80K miles). I've put 110km's on it in the past 2 days and Iv'e used over a quater of a tank! Mind you it has been alot colder now then last week and I've had the heat on more, but other then that I don't see how it can be so different?

What could be causing this? Bad Air Filter? o2 sensors? Sure my driving style could contribute a little, but I drove my mom's harder then I have mine so far...

Ummmmmm....you actually have zero idea if you are getting different gas mileage. As mentioned above, you have to divide the miles/km driven by the KNOWN gallons/liters used. You also need to average it over more than one tankfull to take into account variances in how "full" the tank is when you stop pumping. There is no way to know unless you do it that way. The gas gauges may be calibrated differently (gas gauges are an estimate of how much fuel is in the tank, they are not accurate), fuel tanks may have been filled differently (one person's "full" may be different than another's, and the gas station nozzles may shut off at different pressures), fuel tanks are different size, etc.

 

[JDraper]

Fuel filter has nothing to do with gas millage, air filter yes. If the fuel filter is plug, poor performance and bogging down or power dying under load and heavy peddle pressure. This is no different than any other vehicle or engines symptoms.

On the newer computer controlled motors, the fuel filter and air filter condition will not affect gas mileage because the MAF and 02 sensors compensate for the air or fuel flow into the motor. Performance will suffer, but However, if the filters are clogged to the point that the computer can't compensate, it will affect your mileage, but you most likely will see a CEL light when the computer can't resolve the a/f ratio to it's satisfaction.

In non-computer controlled vehicles, yes the filters will affect mileage because there is no feedback loop adjusting the a/f ratio.

 

[shadowless127]

On the newer computer controlled motors, the fuel filter and air filter condition will not affect gas mileage because the MAF and 02 sensors compensate for the air or fuel flow into the motor. Performance will suffer, but However, if the filters are clogged to the point that the computer can't compensate, it will affect your mileage, but you most likely will see a CEL light when the computer can't resolve the a/f ratio to it's satisfaction.

In non-computer controlled vehicles, yes the filters will affect mileage because there is no feedback loop adjusting the a/f ratio.

But think about this, if your performance is not as you usually want it, you're going to push the throttle in MORE to compensate on your end; therefore using more fuel.

 

[tripplec]

Well I did some testing this weekend. However it did not work out quite right. Maybe more time is needed. I have a Scangauge which collects computer input and allows me to see what MPG it calculates. I use it to see how the vehicle responds to driving changes.Driving on the Hwy which is a 100k/hr limit at various speeds up to 120k/hr. On grades up it would drop from 26-28mpg to 18-20mpg on slightly more throttle. Quite a drop in my opinion. I have a Grand Cherokee 4L I6 and the difference is minimal. These are NOT hills but super highway grades up and then down. W

Well I though maybe I should let the computer recalibrate. I disconnected the battery and while at it cleaned the posts and terminal. After over half hour reconnected and on the trip back home 200km. It was registering mostly around 15mpg to 17. About 9mpg less than before. I hoped for it to reconfigure itself by the time I got back. The weather as much warmer as well, 6 Celcius back and -8 to -11 on the on the way down. What really puzzled me is the computers indication of engine load was 70-85% on the highway much higher than any other vehicle I have used it on. At idle it was 42% in Park!!! Hmmm

Now what, will it recalibrate itself back and how long?

 

[stsmoker]

Is the only syptom for the low gas mileage the low gas mileage? Any weird noises, any driving difference, RPM's, Engine Temp..

 

[tripplec]

Disconnected battery, now low gas millage

Yes, that is the only symptom. I filled up for the trip back and it used much more visiable on the gas gauge. Drop was almost double and all highway driving 100kph+ except for the last 20km. The same route taken in the past.

Although this is not related. I noticed before the change and now that OD only improved millage in certain level crusing places. OD Off generated higher readings on the slight grades everytime and lower Hwy speeds, as well as some higher situation. Tach variation could be about 500RPM depending on speed in toggling OD on and off at the speed I would be travelling at.

Back to the computer, what does it base its mixture settings on. I have read where people cleaning air flow sensor needed to have the computer recalibrate itself by disconnecting the battery to reset it.

 

[shadowless127]

Yes, that is the only symptom. I filled up for the trip back and it used much more visiable on the gas gauge. Drop was almost double and all highway driving 100kph+ except for the last 20km. The same route taken in the past.

Although this is not related. I noticed before the change and now that OD only improved millage in certain level crusing places. OD Off generated higher readings on the slight grades everytime and lower Hwy speeds, as well as some higher situation. Tach variation could be about 500RPM depending on speed in toggling OD on and off at the speed I would be travelling at.

Back to the computer, what does it base its mixture settings on. I have read where people cleaning air flow sensor needed to have the computer recalibrate itself by disconnecting the battery to reset it.

do yourself a favor, leave OD on unless you're towing.