Getting some horrible gas mileage... help?

[CruseadorPT]

Recently bought a 03 limited with almost 93k miles on it and its got some bad gas mileage. Last time i was mostly highway and only got 162 miles between fill up. any ideas on what it could be?

added info:

recently changed the spark plugs for some bosch +2... the ones that have two metal thingys at the end except 1... lol dont know about mechanical terms.

[Candace]

A few things you can do to improve gas mileage is

1. Fixing a serious maintenance problem, such as a faulty oxygen sensor, can improve your mileage by as much as 40 percent.

2. You can improve your gas mileage by around 3.3 percent by keeping your tires
inflated to the proper pressure. Under-
inflated tires can lower gas mileage by 0.3
percent for every 1 psi drop in pressure of all
four tires. Properly inflated tires are safer
and last longer.

3.Use the Recommended Grade of Motor Oil
You can improve your gas mileage by 1-2 percent by using the manufacturer's recommended grade of motor oil. For example, using 10W-30 motor oil in an engine designed to use 5W-30 can lower your gas mileage by 1-2 percent. Using 5W-30 in an engine designed for 5W-20 can lower your gas mileage by 1-1.5 percent. Also, look for motor oil that says "Energy Conserving" on the API performance symbol to be sure it contains friction-reducing additives.

4. I have always been told also that a clogged air filter causes bad gas mileage, howevr, I found this
NEW INFORMATION:
Replacing a Clogged Air Filter on Modern Cars Improves Performance but Not MPG

A new study shows that replacing a clogged air filter on cars with fuel-injected, computer-controlled gasoline engines does not improve fuel economy but it can improve acceleration time by around 6 to 11 percent. This kind of engine is prevalent on most gasoline cars manufactured from the early 1980s onward.

Tests suggest that replacing a clogged air filter on an older car with a carbureted engine may improve fuel economy 2 to 6 percent under normal replacement conditions or up to 14 percent if the filter is so clogged that it significantly affects drivability.


That's a few things you can check,
also driving at a lower speed, such as 55-60 helps gas mileage performance by like 4%.
spark plugs was an excellent thing to do, I would check tire pressure next and be sure I have fresh oil of the proper type reccomended and go from there. O2 sensors ( for my 2001 limited) was about $70, but worth it.

I recently done some research on this subject, and that's the information I kept seeing time after time. Hope it helps.

[quicksilverdon]

Originally Posted by CruseadorPT

recently changed the spark plugs for some bosch +2... the ones that have two metal thingys at the end except 1... lol dont know about mechanical terms.

Did you change the wires? The wires go bad before the plugs do - and you should always do both - wires and plugs. The plugs should be gapped at 0.040.

[mopar_man]

Originally Posted by Candace

NEW INFORMATION:
Replacing a Clogged Air Filter on Modern Cars Improves Performance but Not MPG

I don't know how that's possible. The engine would be working hard to get air through a dirty filter, causing a loss in MPG. If we went by that statement, we would never have to change our filters. Other than that, what you've stated is a good starting point for figuring out the problem.

Is there a check engine light on? It's in the lower left gauge. It's orange and is roughly the shape of an engine. Also, have you had your timing belt changed yet? It's due if you haven't.

[Hooligan]

There is a "sticky" at the performance section that tells you the specs and correct way to change the spark plugs, including the materials to use when doing it.

[Travis2k7]

Just remember you aren't driving a Honda... 20-24 MPG is about all you are going to get in city traffic.

[Hooligan]

Originally Posted by CruseadorPT

Recently bought a 03 limited with almost 93k miles on it and its got some bad gas mileage. Last time i was mostly highway and only got 162 miles between fill up. any ideas on what it could be?

added info:

recently changed the spark plugs for some bosch +2... the ones that have two metal thingys at the end except 1... lol dont know about mechanical terms.

Electrodes is the proper name. You have to figure the mpg you are getting, and then let us know. 162 miles divided by number of gallons = MPG or go to Fuelly | Share and Compare Your MPG and enter the info.

[geronimo]

Just remember you aren't driving a Honda... 20-24 MPG is about all you are going to get in city traffic.

162 miles per fill up is around 13-14 mpg. That's right around h2 mpg range.

These are all great posts with some good advice. Another quick test to perform is to listen for any hissing or suction sounds coming from your engine at idle. If it sounds like there's air being pushed out or sucked in you may have a vacuum leak, which is a big mpg killer.

Some places to check:
1) all Vacuum hoses
2) Throttle body gasket
3) TB shaft warpage
4) Intake Manifold Gaskets
5) Check intake manifold for warpage
6) EGR Valve (not sure if the 03 limited has one)
7) Valve cover Gasket

Hope this helps, good luck.

[Travis2k7]

Originally Posted by geronimo

162 miles per fill up is around 13-14 mpg. That's right around h2 mpg range.

It's actually 10.8 mpg which I knew when I read the original post by doing some quick math... (162 / 15 gal tank = 10 something)

I was just pointing out that AFTER he gets his problem resolved to not expect more than 20-24 mpg because you aren't going to get it city driving a PT.

[edsidders]

Originally Posted by mopar_man

I don't know how that's possible. The engine would be working hard to get air through a dirty filter, causing a loss in MPG. If we went by that statement, we would never have to change our filters. Other than that, what you've stated is a good starting point for figuring out the problem.

Is there a check engine light on? It's in the lower left gauge. It's orange and is roughly the shape of an engine. Also, have you had your timing belt changed yet? It's due if you haven't.

Computer compensates for reduced airflow by adjusting the fuel air mixture , Just loose power -- with carburetors there was no compensation for reduced airflow in most american carbs,just flow the same amount of fuel and less air. The old British SU carbs would compensate to a certain extent....I'd look at a plugged exhaust on this one after changing the plug wires and checking the engine codes..