i have a '94 f150 4x4 with a 302 and it is getting TERRIBLE gas mileage..i had a job interview 140 miles away and it used $80.00 worth of gas just going there and 80 back,this is rediculous..a friend of mine has a '97 f-250 4x4 with a 351w and i burn twice what he does on the same trip...ive installed a k&n air filter and new plugs,wires,cap,rotor im all out of idea...is this normal? ive either got to bid this truck farewell or find me a 300 inline 6 to go in there..any ideas would greatly be appreciated

 

You are right: This mileage is nowhere near normal. While you do not say what your price per gallon is, I calculate (based on gas @ $3.30/gallon) that you are getting less than 6 MPG. You have done some of the basics that should help. Check to be sure that your front hubs are both disengaging. How long since you changed your O2 sensor(s)? What is your exhaust system like? Factory? Modified to one degree or another? Either way, is there some form of blockage: crushed pipe or deteriorating catalytic convertor? Is your thermostat working properly? A cold engine burns more fuel than one reaching proper operating temp. What is your base timing? How hard are you driving it? Is your overdrive working properly? What about your fuel pressure regulator? How many miles on the odometer? What is the power like? Perhaps a compression check is also in order.

This truck should be MAF with SEFI; and as such should give MPGs in at least the mid teens; upper teens if you drive with an eye toward economy - and a light right foot.

You do not say how much history you have with this truck, so is this a new occurrence after it having been running better; or is the truck relatively new to you?

Please provide some more info/background and there are many on here who can and will provide you invaluable help.

If your truck were a person, given its excessive thirst, it would be highly likely to be diabetic!

dn.

 

thankyou for your reply,gas here is 3.35 a gallon...yes i forgot to mention it has dual exhaust with no converters,32 inch tires and 3.31 gears,im taking it tomorrow and getting some of the sensors checked out..im about to invest in some 3.73's or 4.10's

 

Lower gears won't help highway fuel economy, quite the opposite actually.

 

the mileage on my 5.0 mustang picked up quite a bit when i changed O2 sensors and changed the fuel filter

sounds like you need a tune up in a bad way. check codes and do a tuneup

 

That's not necessarily true. Best milage is obtained at the highest speed the vehicle will maintain with the lowest rpm and highest vacuum. These trucks have lousy aerodynamics so best milage won't be obtained at speeds beyond 60-70mph anyway. Some of these trucks were handicapped with bad drivetrain mismatches like a 5.0 with 2.73 gears. In this case changing to 3.55 or 3.73 gears(or more depending upon tire size) will improve milage because engine load decreases even though rpm increases. The most extreme example I can think of was a car belonging to a friend of mine, it has a 360 with 3.90 gears and would turn 3500rpm cruising at 65mph, but got 15mpg because the throttle was essentially closed(very high vaccum, very light load).

 

that makes alot of sense...what gearing would you recommend for my setup?..some say 3.73's while others say 4.10,im not sure which way to go...also does a throttle body spacer work aswell? ive heard good and bad about this aswell...oh,i wanted to ask about plugs...ive always ran ac delco R45TS,they have always worked good for me

 

3.73 or 4.10 with the 32" tires, and you need to fix whatever is wrong with the motor, because even with the tires and gearing you have it should get better milage than it is right now.

 

get your injectors flushed. throttle body spacers are a waist of money, just get a throttle body by profesional products or bbk, id check or O2 sensor, wheres was it located? if its after the cat on the exhast thats the problem. in my 95 i easily get 18mpg doing the speed limit with no on comming wind and mines lifted! change the fuel filter also like past mentioned, your timing could also be off so also get it tuned up like also mentioned...

 

the o2 sensor it still behind the convertor...ive had both convertors taken offwith 2 1/4 inch exhaust with glasspacks...i do need to get the injectors flushed and a new fuel filter im sure...i noticed you have 4.10 gears with lockers....is it alot more to get lockers than just a 4.10 open diff?

 

theres ur fuel problem. ur o2 sensors pickn up the wrong reading meaning its trying to compinsate makin ur truck run like a pig... u need a cat in there to fix it, get a high flow one if you got the money... change out the fuel filter is also a good idea.

i have no clue about the lockers being more then open diffs, never looked into them before. I went with lockers because my spider gears were worn out and plus i was going to be doing some 4X4ing on the side of being an every day driver. I have an eaton electric locker up front (wired into my push button 4X4) w/manual warn hubs and a detroit locker in the back... my gears i got through a shop here in Edmonton, Alberta, Canada, called The Gear Center... my lockers came from there too... If I were you, and something i should have done but didnt, upgrade your axles too... mine havent broke yet but they are starting to wear.

 

another thing. i was readin one of your last posts and it said about plugs, get a different set of plug wires and that will help and a fresh set of plugs. If your got the cash, a new distributer would be an ok investment along with MSD spark box... A cheap thing you can also do, rather then getting the MSD box (I was told this but havnt tried yet) was up grade your power/ground wires from your alternator. change it to 4 gauge for stock 8 and it will increase the spark with less resistance (Stereo comp. guy told me this). Id also go with the MSD box just incase