Thread: F150 MPG Blues
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Old 07-08-2013, 02:06 AM   #1 (permalink)
Noahfreak
EcoModding Lurker
 
Join Date: Jul 2013
Location: San Diego
Posts: 18

Goldy II - '94 Saturn SC2
Last 3: 26.24 mpg (US)

The Beast - '88 Ford F150 XLT Lariat, Supercab, Long Bed
90 day: 13.61 mpg (US)

Domo - '89 Honda Civic Wagovan
90 day: 30.49 mpg (US)
Thanks: 2
Thanked 1 Time in 1 Post
F150 MPG Blues

Hi Everyone,
I'm new to the forum and already enjoying the wealth of information I've stumbled across. A couple years ago I bought an '88 F150 2wd with the 4.9L I6, Mazda 5-speed and 3.55 rear gears thinking that I'd be able to get decent gas mileage with it. Well, I was wrong, at least so far. My best tank so far has been 15mpg and that was everything I could do that I know of to conserve fuel.
Since getting the truck, I proceeded to mechanically restore it to stock condition before making any eco-type improvements, so I've rebuilt the engine, rear-end (added a limited slip 'cause it only cost another $50 or so compared to rebuilding my original carrier) and I'm about to swap transmissions.
The truck has all brand new ignition, new injectors and as far as I know, the engine is running as it was designed to. Unfortunately, that still means that it's extremely bad on fuel and that it isn't all that powerful.
I have decided to switch from the M5R2 Mazda 5-speed to a ZF wide ratio 5-speed rather than rebuild the current transmission. The ZF has a higher numerical 1st gear for easy starts, especially loaded, and a numerically lower overdrive, hopefully getting my engine below 2000 rpm while cruising at 65 mph. It's also much heavier-duty, so hopefully it will last longer than the current one did.
I decided on all of that before discovering this forum, but man I'm glad I found you guys. My thinking was correct on the transmission mod and making sure the engine is running right, but there's so much more to the puzzle than I originally knew to maximize mpg. There's already a vacuum gauge in the mail for this truck, and I got another one for my 1994 Saturn SC2 even though that thing is already amazing on fuel. I also have a Ford-specific OBDI scan gauge for the truck on the way as well. I think some of the old sensors might be sending faulty signals to the computer. The check engine light is not on, but apparently this could still mean some sensors are out of whack.
There's no way this thing should be so bad on fuel the way I've been driving it. My father's old '77 F250 4x4 crew cab with the 4-speed non-overdrive manual behind the 351M motor would beat this by about 5 mpg, and that's with a carburetor, so there's definitely some improvement to be had.
As far as the Saturn goes, I added a less restrictive intake, hotter ignition coil packs (so I can gap the plugs a little wider), put in new injectors and generally just keep the car well maintained. When I bought it, it was averaging about 23 mpg city and about 26 mpg highway, which is terrible for such a small aerodynamic car. With the cheap mods that I did, it bumped it up to an average of 28 mpg city and a max of about 42 mpg highway. I average in the high 30s on long trips usually. I'm hoping that by adding the vacuum gauge I'll be able to get it into the 30s in the city with daily driving, and bump my best 42 mpg up into the high 40s or maybe even 50 mpg. For the truck, I'd be ecstatic if I could get into the 20s, which I'm sure with some dedicated effort, I will exceed.
I think with the help of these extremely knowledgeable forum members, I'm already well on my way to making these vehicles into the fuel sippers that I hope they can be. Thanks already to those who have provided knowledge. I can't emphasize enough how beneficial that is to the rest of us.

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