Pitiful gas mileage - no indicators?

[Curt Brubaker]

Trying to gauge if I'm off base here with my mileage. 01 4x4 ST.



When I bought my trac they did an o-ring replacement in the intake because it had a CEL and was blowing black smoke.



I had been seeing 300 miles to a tank of gas, on a rarity it'd see maybe 320 miles or so to a full tank (87 octane) after that.



I recently put a shackle lift an did a TT, as well as added 15"x8" dick cepek aluminum wheels with 31x10.5" Mickey Thompson mud terrains on.



I also just replaced all the plugs and wires (motorcraft...I had issues w/ NGK at first) and thanks to this site it got narrowed down.



Anyway, my last tank, I got 199 miles before it was necessary to get gas or walk. I think this seems pretty poor. This has been the norm for the past 6 or 7 tanks of gas. I drive light footed, and it is mostly city so I expect a bit lower, but the 10mpg or so that averages to just doesn't seem right.



Nothing has thrown a code, but I'm pointing at the 02's or maybe a coolant temp sensor? I have a new stock replacement air filter, but plan to put on an open air element type intake/filter on shortly to open it up a bit. I have removed the silencer/snorkel in the intake as my only other mod. Otherwise it's stock as can be, 72k miles.



Anyone have any opinions? I drive about 65 on the highway because I know this heavy pig isn't an aerodynamic nightmare. My other thought was to get a bed cover to help w/ resistance a bit but not sure if it'd actually give me a noticable difference or not.



Thanks all!



Curt

 

[Michael Cacioppo]

If your new tires are larger than you're old ones, you'll indicate less MPG on your odometer. Is your odometer calibrated to you tire size?

 

[Curt Brubaker]

It is not, and I figured this would effect it to a point but not sure how much.

 

[Michael Cacioppo]

Curt what were the two tire sizes?

 

[shawn stonbraker 2]

Putting a truck in the air (even a few inches as you did) and putting bigger tires on will drop the MPG. (both by not reading correctly and also by actual drop due to the bigger/heavier tires) Here is a calculator to show you the difference in tires. (from the one you replaced, to the one you have on)

 

[Curt Brubaker]

I had whatever the rolling stock 15" rubber was, they were original, to a 31x10.5x15 mud terrain.



I'll try calculating it out.

 

[Sean M 2]

Yup tires and lift is what did it.... Your fuel economy will suffer with that setup. Also, the mud terrains have a higher rolling resistance than the originals, also contributing to the lower mileage. Try raising the air pressure in the tires, this may gain you an MPG or so.

 

[Curt Brubaker]

Ok so that calculator states that I went from 698 Revs/mile to 658.



Also states my spedo is 6.1% slower, AKA I show i'm doing 60mph, I'm doing 64mph

 

[Richard L]

Regarddless of your tire size, don't use the fuel gauge to measure your gas mileage. The gauge is notoriously inaccurate, especially in the early models. I had a 2001 Job 1 with the standard 20.5 gallon tank and could regularly put in over 22 gallons when it was not even all the way on empty.



The only accurate way to check your mileage is to fill the tank up until you can see the gas sitting at the restrictor plate in the filler pipe. reset your trip odometer and drive at 100 miles round trip back to the same gas pump and fill up again so that the gas is exactly where it was in the filler pipe when you filled up the first time. Now get an odometer reading to the nearest tenth of a mile and the gallons of gas required to fill the tank again, to the nearest tenth or even 100th of a gallon if the pump shows that (mose new pumps do)



Now divide your miles driven by the gallons of fuel used and you have a fairly accurate MPG for that particular day an time under those specific driving conditions.



Your driving habits will make a big difference, as well as the gas you use. Most gas stations have switched over to the winter blend of gas and that nets less MPG. Sometimes switching to a differnet brand will show an improvement. Also, School is in session, people are out shopping for the holidays, etc so the traffic is getting heavier and the colder temperatures means that the engine will run a little richer until it warms up.



It's probably not one big thing that is killing your mileage but more likely a bunch of little things stacking up against you that is sucking up your gas.



,,,Rich