1994 Ford F150

[david85]

If you were to look to some of the stick shift 300 powered pickups back in the mid 80s before fuel injection, they were getting the mid 20s for MPGs. The EPA has since revised its testing method and updated older ratings to show lower numbers, but some are still rated at 23MPG. You can actually track the MPG ratings over the years and there is a distinct drop when fuel injection was installed (along with a slight bump in power and torque). This is of course a 2wd, half ton, likely regular cab pickup with a clark 4 speed overdrive manual transmission (I think it was the clark....).

Generally, the 300 will get better MPGs than a 302, but I don't know if it will ever pay off for you. I've read over on FTE that headers and a well sized dual exhaust can help the 302, but I never tried any of those mods with my truck. Right now its a spare work vehicle that is parked most of the time since the diesel gets better economy and much more power.

I know some one over on oilburners.net that converted a 2wd stepside f150 to a 7.3 IDI diesel and that thing gets close to 30 MPG on the highway with 3.55 gears and 5 speed stick.

[Execut1ve]

I don't expect the 4.9L will offer incredible improvement in mpg, but I expect it to be noticeable. the plan hinges on me being able to sell the engine currently in the truck for as much as it'll cost to buy the 4.9L. I also envision a manual tranny swap in conjunction with the engine swap to net a further mpg improvement

[Execut1ve]

I just did a very rough number crunch and I'm fairly sickened by the results... with gas at roughly $3.75/gal and diesel at about $3.95/gal (in these parts anyway), and assuming 10k mi of driving annually, if I paid $1k to swap a diesel into the truck and managed to average 30 mpg with it, the fuel savings would pay for the engine in just over 10 months

[cleanspeed1]

Originally Posted by Execut1ve

I just did a very rough number crunch and I'm fairly sickened by the results... with gas at roughly $3.75/gal and diesel at about $3.95/gal (in these parts anyway), and assuming 10k mi of driving annually, if I paid $1k to swap a diesel into the truck and managed to average 30 mpg with it, the fuel savings would pay for the engine in just over 10 months

Told ya.

[david85]

It could get worse then that. First, the transmission also needs to be swapped since diesels (in fords at least) are a different bolt pattern (don't believe anyone that tells you a 460 is the same - it isn't). Also, if you are doing lots of short trips with a proportionally large amount of warmup time on your miles, you may actually get mileage comparable to a gasoline engine and in some rare cases slightly worse. The F150 I mentioned, got those numbers on a cross country trip over several consecutive fillups with average speed of 60-65 MPH if I remember right.

The 6.9/7.3 engines also require twice as much oil per drain interval. Other maintenance is generally lower, but I need 10.5L of oil with the powerstroke style filter I run (twice as large, and finer micron rating).

I was lucky with my F250 since it was already diesel and I use it mainly for highway driving. When I first swapped the rear end gears, the mileage improvement was such that they broke even in three months. The transmission swap took longer but did pay off after a couple years.

[Frank Lee]

You aren't gonna get 30 even with a diesel. Do you enjoy torturing yourself? I keep visiting here, I must like it.

It's a moot point though, because you don't have $1000 anyway... RIGHT?

[Execut1ve]

david I actually considered both your points... yes it would mainly (until I move or get another job) be short hops to work, and you are correct that the engine would not bolt up to the tranny, although there are adapter plates that can be purchased. Not that I'm that fond of my current tranny anyway though lol

To be completely fair though, I did not count any money I get for selling the current engine against the price of the diesel, so it's still a toss-up. In all probability, if I do any engine swapping, it'll still be to the 4.9L simply because everything bolts up and if I can get $500 for my current engine I"ll have no net cost but it's sure nice to fantasize about a diesel swap, especially one of the 89-93 12V 5.9L Cummins

[Frank Lee]

Why aren't you fantasizing about a Metro or a diesel Tempo?

[Execut1ve]

diesel tempo? for reals? surely that's a DIY swap lol

I already have the civic to fill that hole in my life, and unfortunately I'm ashamed to say I've gotten a bit into the truck culture I really have enjoyed working on it, although to be fair I might enjoy working on some other car just as much. I just have no experience with that because the Honda has been so trouble-free.

[Frank Lee]

The Civic is not filling any "hole" because YOU don't get to drive it.

I have to laugh at that "engineer" who put up a thread "I drive a big truck and I like efficiency". Yeah, in my engineering world, using a 4000 lb device to move 200 lbs is not in any way, shape, or form, efficient.

OK, so maybe this psychological problem is insurmountable. Would a small truck still project a manly enough image? Cuz then 30 mpg is attainable.

Diesel Tempos are for real. You can read about them here on EM.