Getting into a big full size American pickup truck doesnt make sense for anyone looking for fuel economy, however things sometimes just work out that way. In my case my commuter car threw a rod bearing and promoted my 1995 F150 into daily driver status.

Info about the truck:
1995 1/2 ton 2wd long bed - regular cab with 3.08 gears. Engine is a 4.9 and trans is the E40D. 128k miles.

Recent maintenance: Plugs, wires, cap and rotor button and thermostat.

Reading on these forums about the 300's and their reliability, steady power, and ability to deliver fuel economy. This thread is going to be my quest to find those above. So far this truck has been reliable! I'm encouraging everyone to post their thoughts and suggestions on what to do next to get this truck returning economy that is better than that of its big engined brothers!

Starting point: My mostly interstate commute is returning me around 14 mpg.

 

Given the trucks axle gearing I'm gonna suggest you keep the trans out of OD at speeds below 60mph, because an EFI motor uses more gas under heavy load(low rpm, open throttle, low vacuum) not less so heavy lugging is counter productive.
Other than that make sure there are no codes or other engine issues, if it's a dual tank truck make sure it doesn't have the crossflow problem, and if the O2 sensor is of unknown age put a new one in.

 

Does your truck still have to stock/original cats on it? If so that is probably the huge MPG robber on your truck. I was getting 7-8 until I bypassed mine with a huge drill bit and now I get a little over 10 Planning or removing them and doing all new exhaust after the first of the year. Just waiting on the time and money. Granted I have some other issues as well. Also going with a free flowing intake like a K&N or Spectre drop in filter will help a good little bit. I have heard of 300s getting 25+ And even pushing 30 but never seen it as I have always needed the V8 power

 

Thanks for the replies so far. I checked into what the crossover problem is and I dont seem to be having that - no fuel transfers between tanks and I havent had a tank overflow yet.

I pulled codes a while ago and had an evap code, I should pull them again and see what it has now. At the time I was looking for transmission codes and didnt pay much attention to the engine code. The check engine light doesnt light on this truck yet.

 

I used my 95 as a DD for my 20 mile commute in and out of Boston. Some days it was all highway driving but most of the time it was 50/50 highway and stop and go. I would check my gas mileage every fillup and I averaged between 16.5 and 17.5 Mpg. My truck is a 300/5 speed/2wd/ 3.08 with 235/75/15 tires. I did use dedicated M&S tires on the rear during the winter months. The truck is all stock except for a couple of tune up mods.
The manual calls for 10 deg BTDC and I have it set to 12. The Autolite copper core plugs are gapped to .050 instead of .045 and I replaced the stock spark wires with Taylor low resistance ones. I use 10w 30 and change it every 5k with a Motorcraft filter. I use 87 octane and fill up at the same station every two weeks. I do have a dash mounted vacuum gauge and try to keep the reading as high as possible. I keep the tires at the max inflation rate and keep idling to a minimum.
Since I drive to Maine during the summer months I was able to get some good highway MPG data too. At a steady 60 Mph I can get a little over 20 Mpg, at 65 it drops to 19, 70 mph brings it down to barely 18. I also have a 4500 lb fifth wheeler RV that only knocks it down to 13 mpg at about 55 Mph in 4th gear.
Even though it has over 250k compression is still good. Best engine ever as long as your not in a hurry. The five speed will give you better mileage around town but shouldn't be that much difference on the highway since the torque converter locks up. The auto trans does weigh much more than the manual.
regards
rikard

 

I got out in the rain today and read codes again, I am still getting 327 for the KOEO.

327 (EGR valve position sensor, Pressure Feedback EGR sensor OR EGR Pressure Transducer - signal voltage too low)

KOER had a pass.

I'm thinking one of my next steps needs to be to check the computer for any issues since I have read that is rather common.

 

Don't drive so fast. If you could go 55-60 mph at most, your mileage should get better. My similarly equipped truck gets 16-22 mpg, but I rarely get over 60 mph. I also have a fiberglass topper to weigh it down a bit. Not driving it much lately account no heat.

 

My interstate speed is generally between 60 and 70 mph. Speed shouldnt be keeping me down that much in economy. And this isnt carrying any load other than me and fuel.

 

I get about 18 in mine. 5 speed and 2.73 rear end. I want to go up to 3.08's eventually. Once I get rid of the crap stock exhaust it may go up.

 

Update!

I havent been driving as much due to the holidays, the one tank full I used I got 14.2 mpg with rather conservative driving. I've got two things on my todo list that havent been checked out yet:
1. Oxygen sensor
2. Engine computer

This truck has some equipment installed where the computer is located so its a little more work to get down to it. Once in there I am expecting to find the source of my egr codes.

Before this last tank I checked the Air Filter and tire pressure. Alignment was checked a few weeks ago too.

 

That 327 code could be from a faulty EVR, or a broken vacuum line. As far as the PCM, it's easier to get to it by pulling back the plastic inner fender, rather than from the top of the engine bay.

To expand on rikard's post about ignition timing, plug gaps, and wires: Search for "sixlitre tune up". It involves installing a hotter coil, lower resistance wires, gapping the plugs larger, installing a performance oriented cap and rotor, and advancing your base timing from the stock 10 degrees btdc to 12-14 degrees btdc. How much you advance it will depend on when your truck pings after advancing. In other words, advance timing, drive truck, keep advancing until you hear it ping, then back off a little.

I was extremely skeptical about the sixlitre tune up until I did it to my 95 5.8l. Mine needed plugs and wires anyway, so I invested a little more for the parts, and consistently get 17 mpg hwy in my F150 crew cab.

 

17 mpg in a 5.8L is what i like to hear, what is your gear ratio?

I was able to get over 16 when I had an older 5.0 with 3.55's and other things that make for poor economy. It might take a little while but this 4.9 will one day beat both these numbers....

 

3.55 gears, E4OD trans, 4x4, 265/70/17 tires (roughly 31.5" tall). Of course, this is holding myself back to 65 mph. She'll easily do 75, at the price of plummeting fuel economy.

 

When I first started keeping track of fuel economy my truck was below 11 MPG of all city driving. Over the holidays I was on some country highways (stopping for small towns) about 75% of the time and in the city for about 25% over the span of two fuel tanks. During that time I was getting mid-15 MPG. Nothing to be excited about, but a decend improvement. Recently the check engine light has been coming on and after running the codes its related to the EGR/vacuum system. I'm hoping if I can run all new vacuum lines that I can get up to your 17-22 MPG range and fix the high idle at the same time.

 

I just bought a 95 F250, 2WD, 5.8L, Manual Tran with 4.10 rear, and driving it 240 miles home, I got 17.3 mpg.

The speeds were between 55 and 70 for most of the trip.

I only used 5th(OD?) when I was traveling above 55 mph.