I Have A 1990 Ford F-150 Custom With The 4.9 In It..i Have 33's On Her An Gas Is Just Crazy I Go About A 1/4 Tank A Day But Im 16 So I Drive Every Where Of Course An Have A Heavy Foot Buyt Latley I Been Easyin On The Gas An It Still Aint Much Better.i Kinda Scared To Put My 36's Super Swampers On There In 2 Weekd..would Like To Know The Average Mpg.ther Supposed To Get..thanks,

 

Dude your shift key must be worn out...Well 1/4 tank doesn't really say anything unless you tell us the miles that you get out of 1/4 tank. What gears do you have too?

 

I had a 87 with the 4.9l str6 - yes, it is a gas hog!!!!!!!!!!!!
how many miles on engine?
i had to change air filter and plugs often
depending on the driving conditions it needs a lot of air so watch air filter

 

I would be more worried about breaking the rear end or drive shaft u joints with 36" tires than gas mileage. the bigger the tire the more unsprung weight-unspung weight is hard to manage from a suspension dynamics point. I doubt that the stock supension/shocks are capable of providing enough damping to handle 36" tires. its your gas and your truck- so hose it up any way you want.

 

omg... i have a 96 4.9L I6 F150 (see sig) and i watch my gas go down daily... it has 2 tanks but 1/4 a tank in 2 days is not rare at all... so its really 1/8 a tank... but for a 6 cylinder i think im doing something wrong.. when i first start it up... the engine sounds like a train when im accelerating for 5 or 10 mins..... you can hear it under the exhaust

 

I have had 2 300's and my dad has had two. His 95 2wd SWB 5-Speed gets around 16-17, not sure on the '81 but it was Carbed and a 4-speed. My 92 2wd Flareside 5-Speed got the same. My 95 4x4 Longbed 5-Speed gets 14-15 around where I live then around 17 when I drive to Joplin or Springfield.

 

One of my TAC officers just rebuilt his 91 w/ a 4.9 staight six and 4 speed. He has twin tanks and still burns through that (he does a lot of hunting at West Point, I have gone with him a couple of times) and he gets 10 on a good day. Don't fret they just eat gas, and as an ex. Tanker 1SG he is used to 9 gallons to the mile He even has a light foot but that 4.9 staight puts out so much torque it just screams for a 5th gear it will never see on the highway. They will chew gas so either get used to it or you will cry all the tme (not trying to sound rude)
~Phil

 

customrider
There were several tank options, so you haven't told us anything about how much gas you're using. Measure your actual MPG, but remember that, for your original odometer to be anywhere CLOSE to accurate, you have to install the correct speedo drive gears in the trans/t-case tailhousing. There are calculators all over the net to help you figure what color gears you need. I recommend finding a GPS to check the odometer calibration before & after swapping the gears.

buzz
Your fan clutch may be stuck.

 

if that is part of the transmission... I doubt it.. remember how you helped me a lot with transmission problems... My tranny was overheating from mud and started leaking FAST I took it to the place they almost voided warrenty but thanks to my mom being single parent with no money *wink wink* they fixed it for free... same day I got home it was leaking.. said it was the coolant line or something... then 2 weeks later they said some pully was hand tied and it was not strong enough.. its now been about 2-3 weeks with nothing wrong at all and seems fine.. im sure if the fan clutch was messed up it woulda been fixed by now or they wuolda said something.. ALSO, we have had this truck since 107k miles.. it now almost 17k miles... I can't recall any time we changed air filter or done anything like that.. just oil changes really.... my mom doesnt know a lot about cars so its kind of hard for me to take optimal care of it. :P

 

No, it's the aluminum finned part that holds the fan to it's pully. Normally the fan just freewheels at a slow speed until temps get hot enough, and when needed the clutch locks bringing the fan to engine speed. You should be able to easily spin your fan without the belt and pully turning with the motor off.

Adrianspeeder

 

so adrian if i just reach down after opening my hood, i should be able to spin the fan easily? if not, the fan is prob broken?

 

so the fan doesnt freely spin, the fan clutch is most likely broken? how much would this part cost to be replaced?

 

imo, the most overrated motor in history.
i all screaming 129 hp of my 84 f150 that got 10-11mpg.

sure if it had a stick and 4.10 it pulled great, but what dosent pull great with a stick and 4.10's

 

heh... the 4.9 will outlast any 5.0 or 5.8 v8 if you dont drive it like a viper

 

I have 3.55's and a stick. I've pulled a 1987 Chevy Monte Carlo SS, I'll pulled a '91 3/4 ton Dodge out of a ditch. Not a single problem on either occassion.