hey ya'll

I have question about the mpg on my truck. I'll give you my specs and maybe ya'll can tell me if its normal or if not what i can do to better it.

i have a 1998 4.2 auto f150

tires=265-80-16

intake= modified air box and K-n-N filter <----new

rearend= not sure but its original.

trany=auto newly rebuilt

millage=100500

driving style= like i just stole it!! haha

the truck is in nearly mint condition with little to no blemishes.
plug wires look great with no cracks and are still very plyable.

fuel filter i think was changed last at 57000.

when i got the truck i was getting 300 miles per tank of gass. then i put on new tires 265's from the original 255's and it droped to 260 miles per tank. then i added the air filter and box mod and am now getting 300 again. Almost all of my driving is highway at about 75-80 miles and hour<-- which is normal seeing that the speedlimit here is 70. i drive 100 miles a day 50 miles each way to my office or somtimes farther if i have to go visit one of my other offices. i think my tank is a 25 gallon tank. when i fill it i only use 93 with the occasional fill up of the cheap stuff. when i fill it i can only get in about 22 to 23 gallons and i figure theres always 2 or 3 left in it so i think its a 25 gallon tank.

anyhow if thats normal for my set up to be getting let me know.

if not what can i do or what should i look into getting fixed
any info would be great.

PS i am more then willing to scrifices alittle performance for beter millage if that helps ya'll with any ideas. i used to have a four banger ranger with 38 inch tires and that thing got almost the same millage as this stock truck so i'm really buged about it


thanx
Keith

 

Well, I don't claim to be an expert on the subject, but I think I can help you out a little bit:
First, if you really drive like you just stole the truck, there is your first problem.
Also, it appears that your tires are larger than stock, so bear in mind that even though your trip odometer says 300 miles, it may actually be slightly off. I don't know the exact way to calculate it, but basic reasoning says that if your tires are larger they are not rotating as many times as your smaller ones, so the odometer may be a little bit off. Look around this site a little bit and you should be able to figure out the exact difference from your stock tires.
Next, if your fuel filter was changed at ~57,000 and you're now at over 100,000 using the same one, then changing that should help.
Now, even though 75-80 mph may be legal in your area, that kind of speed is not the best way to maximize your mpg.

 

Replace the fuel filter, clean the MAF, and enjoy driving your truck.

Do you have a chip that makes use of that 93 octate gas? The factory chip is programmed to run 87 octane.

 

well i do not have a chip but i cant stand all the knocking and pinging that i get when i use 87. everytime you step on the gas when i use 87 it will hessitate and pink and it drives me nuts. besides i liek to think of it like this. if 87 cost me 1.57 a gallon and 93 cost me 167 in the end its only a bit of 2 dollars more for a ping free truck. well worth it as far as i'm concerned. in my area they even have 102 octane at the pumps. its like 50 cents more a gallon so i never bother with that stuff.

 

Change your fuel filter as mentioned above, and go back to P255/70/R16 tires. A dual exhaust will help your milage a little too. Considering you drive 75-80 mph, a dual exhaust will help your engine breath better, and run more efficient especially at those speeds. Those 3 steps will gaurantee you better mpg.

 

thats why you dont but premium in the first place because if you switch back you are going to here the pinging, so dont do it unless you have a chip, and a dual would help....