Super bad gas mileage
 

Over the past few months, I have put in a new o2 sensor, mass air flow sensor, air filter and most recently a new fuel filter, and ran a bottle of fuel system cleaner through. I run my tires at 35 psi, but my gas mileage keeps getting worse and worse. I havent found any leaks along the line. Most recently, 3/4 of a tank of gas got me 200 miles, thats about 10.65 miles to the gallon. I have the 4.6L V8. I cant figure out why its doing this bad, espically when i have had all this stuff done to it. Ive heard something about gas being switched over to a summer formula? I dont know too much about this but i dont think it would make my mileage go down that much. Any idea, im really lost on this one.

I have a big problem with my gas mileage as well. I have a 4.2L V6 engine and I get the same gas mileage as you. I just recently changed out my O2 sensor so hopefully it will make a difference. I normally get about 11.5 city and 14.8 on the highway. If this doesnt work I Need Help.

when was the last time you changed your spark plugs?perhaps they r worn out and you arent burning like u should b

last time i had the plugs changed was in december of 04, also had new coil packs installed as well. I recently put on a mac products cold air intake, a raised throttle body and a pulley underdrive kit. On my 4.6 V8 i now average 18mpg with highway, city and off-roading. I usually do atleast 30-45 minutes minimum of off-roading on each tankfull, average highway speed is 70-75, city makes up the rest. Signifigant increase in mileage id say, love the 30+ extra horses too :). havent gotten a chance to see what just highway would be but im going to college in pa in october so ill be able to figure out my highway mileage then and i will let you know what it turns out to be. I also installed a toneau cover but sadly the thing is a piece of junk and 7 snaps have already broken off so i havent had the opportunity too see how that helps out. ive heard it adds about 1-2mpg. I am ordering an ignition booster within the next few days so hopefully that will help out as well. the numbers posted for the ignition booster are 10-12 horse power and lb-ft of torque and close to another mile increase in fuel economy. REcently started adding marvel mystery oil to each fill up. ill let you know how it goes. My goal one day is to be able to get 25 mpg out of my 4.6 on highway, i know it sounds like a long shot but there are still many more things to do to increase mileage. thats all for now 8D

p.s.
tire pressure is 40 psi on p265/75/r17 cooper discoverer atr's (great tires)

I was just gonna say put the tire pressure at manufacturers specs unless the tire size is differant than run 5-10 lbs less than max the tire says. With radials you want the correct air pressure or your working against the tire and not with it.

I am currently getting about 22-25(25 on a good day) all city in my 2.0L 4 Cil Focus. I should be getting from 25-28 city. My girls Focus with 2.3L 4cil was getting about 30-31 highway and I think she just pulled close to 35 out if it by staying under 70MPH and under 3G RPM. I got 23mpg when I drove in the city and very rarly brought the car over 2G RPM.

go check out the 4.6 Mod motor forum to see what the guys ofer there say.

A moderator is gonna come in here soon and say the same thing anyway.

Hi Mr. Moderator :)

Well as of now the truck has been holdin steady at 21.5-22mpg on the highway. i just put a fuel additive called XTane into the tank. it claims a 20% minimum increase in gas mileage on any vehicle and up to 35% maximum. Im driving up to michigan from PA later on tonight so ill let you know how it goes.
still on my never ending quest for better gas mileage

-keyul

hey, hate to keep reviving this but i figure ill keep letting you guys know about mileage on trucks and what really helps. i tried out that xtane stuf, i ordered the 4 pack, 4 total fluid ounces per bottle. i used all 4 of the bottles. my mileage jumped up to 23.5 on the highway at 60-65 mph. had i ordered more and kept using it that number probably would have been higher. next up is intalling my igniton booster, long overdue but i went to install it and realized the store sent me the wrong unit. im gonna be heading home for thanksgiving so i will be able to see if the booster helps out any. i know it will help out with power but with gas, im not so sure. best other upgrades to get that will help out with gas and power are gonna be an electronic radiator fan and a set of headers, plus exaust. ill let you know how it all goes when i get it done. i hope this information will help you in saving some $ on gas as it has helped me. by the way, whats gas runnin out there back home in ct? out here in pa its been 2.17 for about a week and a half now.

-keyul