Hello All,

Just picked up a 99 3.0 im averaging about 10 MPG right now, and I do drive like a old person. It is bone stock, i did just put factory size tires on it (had some mud tires on it before). Any tips and tricks to help it pick up in MPG?

 

Welcome to the forum

Yes, something wrong with the math here, truck wouldn't drive at 10MPG it would flood out 1st with a cloud of grey smoke out the tail pipe

Have you checked the speedometer and odometer for accuracy?
Mile markers on road or GPS APP on phone

Only other thing would be you are leaking fuel or have a neighbor kid with a siphon hose, lol
In the summer months you WILL SMELL a fuel leak, for sure

3.0l was no fuel saver, expect about 18mpg maybe 20 on a long road trip
O2 sensors need to be changed every 12 years or 100k miles whichever comes first, they help computer get best MPG

Pull out a spark plug or two, have a look at the tips, very light brown color is expected, darker color means Rich running, change the O2s ASAP

 

Yes welcome! RonD's advise is spot on. I have a 2003 automatic with almost 267K miles. I have not experienced low MPG as you stated but it was closer to 17 to 18. After replacing the oxygen sensors and staying on top of maintenance intervals including recently sending out the fuel injectors for service I can get 21.5 on 1 hour + trips on the freeway at speeds of 75 or 80. That to me is very impressive.

 

Were the tires you took off to put factory size on, larger or smaller than factory? There is a chance the previous owner re-geared it for that particular size.

 

ill pull one today when i get a free chance. im guessing theyre still factory O2's due to the previous owner admitting he knew nothing about cars.

 

Tires were the same size as factory, but it being a mud tire makes them very heavy compared to an all terrain tire.

 

no smoke coming out of the tail pipe at all. when parked after a drive i can smell fuel closer to the tank. There is no residue of a leak in the fuel tank area.

 

UPDATE: pulled the plugs as suggested above, and they look fine. car is not running rich at all. at this point im leading to a bad fuel tank (could have a small hole somewhere that is allowing the fuel to evaporate)

 

Yes, check filler tube its often cracked so leaks fuel when driving

You can do a simple test with a helper
Get a short hose and damp towel/rag
Take off gas cap
Put end of hose in filler and wrap towel around it to seal it, hold it in place
Blow into the hose, tank should hold pressure
If not you should hear the air escaping, see if you can find out from where

DO NOT use an air compressor for this test, you WILL blow off fittings
Human lungs can generate about 2psi MAX, this will not blow off fittings.........unless you ARE the big bad wolf, lol

 

yes that is my guess, and if its leaking fuel when driving that would explain why i can smell it after driving it.