I have a 94 F150 with a 4.9, 4speed with OD manual trany and 3.55 rearend. I do very little towing. Mostly city driving with some trips in to the mtns. I get about 15 miles to the gal. I would like to get more if possible. Would swaping out the 3.55 rearend to a higher set. Would be worth it? Any thoughts?

 

Your not gonna get much more if any with a 3.23 or a 3.08 gear set. Your actually getting better mileage than most of us here with the six. My 93 with 3.08 will get 14.5-14.8 consistantly on either tank not towing and 12.3-12.6 towing a 4200# trailer thru Maryland & Virginia. But I'd love a 3.55 set in the rear to bump my Towing Capacity another 1000# and possibly my mileage towing.

If I were you I'd leave it alone. Don't do a thing other than regular maintenance, etc.

Larry

 

I drove a '95 F-150 with the 4.9L I-6, 5-Spd, and 3.55 gears for about 2 years, and 15 mpg was about average for combined city/hwy driving. Straight highway driving was better I'm sure, but I didn't take too many long trips.

My dad has a '92 F-150 Super Cab with the 4.9L I-6, automatic, and 3.55 geras. On a recent 250 mile trip, it got something over 18 mpg averageing 70mph. So it is possible to get some fairly respectable numbers, but I think if I were you I would keep it stock and just stick to routine maintenance.

 

I have 2.73s and no, it won't get you any better mileage unless you do lots of highway.I get around 14 in the city. The only time it comes in useful is when I'm doing 75+ on the freeway.

 

Glad I didn't get the six when I bought mine! I get up to 18 mpg on the highway and usually around 14 in town. 302 AOD 3.55 gears.

Made a consistent 9.5 mpg pulling a 6x12 enclosed U-haul through the mountains on my recent 1400 mile move to Arizona from North Dakota. Oh yeah, heavy topper on the pickup was also loaded to the top, poor old girl was about 1/2" from the bottoming out bumpers...

 

I got 17.7 mpg front tank (equal city/highway) and 14.5mpg rear tank (light hauling/stop & go) in the first 455 miles I owned my 1988 300/m5OD/3.55 longbed. Stock, tailgate up, A/C, maybe a dysfunctional EGR and a small vacuum leak. I drive with a pretty light foot.

I hear a tonneau cover or bed cap will give you a few extra mpg, as will a less restrictive muffler. Looking at EPA mileage estimate, the 300 with either overdrive tranny will give you the best mileage, 16city/20hwy.

Some people swear by the 302/overdrive combo. I know a 1990s conversion van that does respectable MPG numbers on the highway and is approaching 400,000 trouble free miles on original components, fluids changed regularly.

 

bed cover, k&n, cat back, taking the pulley off of the air pump that all help a lot

 

Agree with that 100%! I also bumped base timing to 12 degrees, and did a little something to the Cats that magically makes them sound "hollow" .With these mods, my longbox, 2 wheeldrive, 5 speed, 3.55 geared truck has seen 22 mpg down the interstate with my heavy foot. Its always averaging in the upper 18's.

Routing the belt to bypass the airpump can be a little tricky. It takes a little modifying of the alternator bolt and bolt spacer.

 

The air pump takes a very small amount of power and will end up causing more problems by removing it on a stock setup.

 

Well put... Should be noted that the pump is a requirement if your Converters have not been illegally tampered with and for proper EGR functions. But, when people are in search of maximum milage, that very small amount of power is just a little bit given back to the motor, and every bit helps, especially when its free power!

 

Would you recommend a tonneau cover or a truck cap for the best mileage?

I'm going to leave my emissions system intact and functional, though maybe not OEM parts. We have bad traffic in Northern Virginia and no cross-state breezes like they do in Florida. I'd just as soon not show up to work brain-dead and high on gasoline vapors.

If the smog pump is taking lots of power, it probably needs attention. It's not moving that much air, I don't think.

 

Truck pictured gets around 16 combined. Seems the faster I go the better it gets. Would a lower gear than 3.55 help mileage???

 

My truck on my last tank of gas when I filled up (today) got 18mpg in almost complete highway. 29" Tires, M5OD, 300ci, and a 3.08 rear end. I was so proud of her.

 

Actually, by removing the air pump from the system you will get worse fuel economy. It helps the cats stay clean, prolonging their life. If you want to help by changing the emissions controls do it the legal way and use a high flow cat.

 

A couple of things that you could do to improve your mileage. One, reroute your belt around your steering pump. You'll pick up several ponies here, and with those also a bit of efficiency as well. There are a number of people here who, when their power steering pump failed, they just rerouted it and picked up higher mileage numbers. Also, electric fan. Both of these are basically just trying to free up drag on the engine. You can either do big mods to improve the efficiency, or you can reduce drag to do the most with what you've already got. I doubt you want to go the way of big mods.

Tonneau Cover
Power Steering Pump Reroute
High Flow Catalytic Converter
Higher-flowing Exhaust
New Intake Airbox & Filter

The above are all the 'quick' things that you can do to pick up power. Tonneau cover will run you probably 200 plus (right? Bedcover may be quite a bit less though..), New belt will be 25 max, Catalytic converter will be 50-70, rest of the exhaust 150-200 dollars at a good exhaust shop, new intake will be 15 dollars (home made) or 50 or 60 dollars, and the filter will be between 20 and 60, depending on if you go with K&N or a competitor - I doubt the 300 will really care which one.

Besides this, just remember the speed limit. Especially with your 4-speed. 15mpg with a maximum of 1:1 in the gear box is pretty damn good, if I might say so. With my 5 speed and a 3.08, I can only manage 3mpg more (though I have a feeling my actual numbers are 19mpg highway/10-11mpg town), so don't worry about it. Going the speed limit will be your greatest help. Stick right at 55, and right at 65 when applicable. You lose roughly 1mpg per ever 5mph over 55 you go. Just food for thought. Happy hunting, and good luck.

Btw..I just figured above I'd recap everything that has been said, in addition to my own. ^_^