hello, i was wondering if anyone can help me...i have a 96 f250 v8 5.8 reg cab. the truck runs great i have duel exaust and k&n air intake. i filled the tank and reset the trip and figured out my mpg is abut 7 miles to the gallon> i thought for sure i would get at least 10> so i adjusted my driving and im still getting about 7> i havent changed the plugs because the truck runs so good> i did notice that all 4 tires had 30pound of pressure and the call for 65. i was wondering if driving on low air pressure would effect mpg that much...thank you for your time. Louis

 

yes it will affect it that much and ware ur tires out... inflate them back to what the tire says and ur mileage will go up

 

wow. thanks. i got them back up to 65 and i guess having all terrain tires doesnt help. thanks for the reply. i also was wondering how i would know if i need a pcv valve. i got the truck at a auction and there is a brand new one in glove box. i was thinkin the preveous owner never got around to changing it. i know nothing about it lol

 

take the pcv valve out and shake it if it rattles its good and well if its doesnt its time for a new one

always glad to help

 

I beg to differ, 30 PSI presure is enough in 8 or 10 ply tires to carry an unloaded pickup without much if any impact on milage or tire wear, so you have other problems. What size tires are on the truck anyway? If they are anything other than the stock size make sure your speedo is accurate and correct it if it isn't, and then check the milage again. If it's still that low start looking for other problems, pull the codes and check for fuel transfer between tanks, those are the two big things with tank crossflow potentially the biggest problem.

 

That's odd Paul... for if I air my 10-ply's down to 35psi they look quite flat. Softer, nicer ride and all, but way to squishy.

I keep mine at 65 unloaded, 80psi if heavily loaded.

of course this depends on the tire.

 

Yep.. much depends upon the tire. I have had the rear(6ply) tires on my truck go down as low as 20psi without looking abnormal.. of course you won't get away with that on the front because it has more weight on it.

 

If there that flat then yes it can kill your gas mileage... if your running larger then stock tires that can hurt your gas mileage... I would write down what your tires are and look them up on the tires website and find out what psi you should be running. Also a cheap easy way to clean out the gunk in your engine is run some seafoam through your truck. My buddys 94 f150 with a 5.0 got about 1-2mpg increase after seafoaming it because all that gunk will decrease mpg and for $8 a bottle you cant beat it. I have a 95 f150 xlt extended cab with the 5.8 running 31" bfg goodrich all terrains and it has 200k miles on it and im getting around 13mpg. A ford dealership manager was the owner before me and had it sense 95 so it gos to show even after 200k miles if its maintained well you can still get descent gas mileage with these trucks.

 

if ur not smart enough to go by the tire pressure on the side of the tire then have fun with a blow out and poor fuel mileage


finding out what psi u should be running.... OMG its on the side of the tire......




srry for all the sarcasm but really u all are suppose to know this



dont go by the door sticker for tire pressure

 

thanks everyone, yes i have a feeling there are other problems as well, was just wondering if tire pressure would effect the mpg that much...and i know the tires take 65psi i have already put that back in and they didnt look that flat....they are the all terrain goodrich tires>and the front tank does not work when i swith to the front the truck shut down and i dont here the pump prime....i think ill wait for it to warm up to correct some of the problems...its freezing here in new york..but thank you everyone for your help> and hitokori i never said i dont know what the pressure should be i didnt know they were down to 35 psi untill i checked they are beefy tires and did not look low on pressure, i was asking how it would effect mpg not what psi i need. thanks

 

I disagree with you. Its been common practice forever to lower the pressure in 10 ply tires to 50 or 60 psi while empty. I've been doing it for at least 15 years. I've never had a blowout & occasionally tow with it that way. Now on a normal 4 or 6 ;ly lt tire I would say it should probably stay within 5 to 10 lbs of the sidewall rating during highway use. If your off road then go down to 15 psi if you want. I'm telling ya It doesnt hurt anything.

 

Once again, you are spewing wrong information without so much as a clue of what you're talking about. The pressure printed on the sidewall is a MAXIMUM tire pressure for the MAXIMUM load on the tire. You're going to wear out the center of your tire in no time with them aired up to the maximum all the time as well as poor handling. The way to decide what pressure to run is to contact the TIRE manufacturer and ask a representative what you should be running in your tire for the vehicle is it mounted on. Then, when you are hauling loads close to the limit of your tire, then you can air it up to fit the load.

 

well if my information is wrong about everything to hear u tell it.... the funny thing is that when i was in high school all my shop teacher said to inflate it by the tire and oh that also means the army musta been wrong to because when i was in we inflated the tires to what was on the side walls..... and i guess Tire Barn USA is wrong too because when i baught those 35's for the ram i had they was inflated to the air pressure indicated on the side wall.....


so i guess if all of those people are wrong then i have been lied to for like.... ever

 

Hitokori -

Just because someone tells you something and seems authorative, doesn't mean they are correct. That applies to everyone - friends, parents, teachers, co-workers, people on a forum, et al.

Most everyone has tidbits of information and only a few have the complete picture - that's okay as it's simply how it is. There are "experts" and "expurts", and the latter is far more common!

Again, this isn't about intent. Most people with bad information pass it along thinking it's correct trying to be helpful.

Each of us as we post need to be mindful that most of us aren't experts, and we can easily (and accidentally) mislead others by sounding like an authority on a given subject.

Also, it is the responsiblity of the original poster to evaluate the answers given and determine which seem to fit his/her particular set of questions most completely.

Above all else, we're here to have fun, make friends, and enjoy time away from the stresses of "real life".

;-)

 

Yes, they all were in fact wrong. If they were running unloaded at a fully loaded rating, the tire pressure was too high.