I don't race them, but the point is I don't get in their way either. I'm usually in a hurry but I don't drive fast just for the hell of it.

I have a 2.73 R/A so I don't use the Mazda's 0.8 OD in the city.

 

The 300 does just fine with a 2.73 R&P. I wouldn't tow with it and I wouldn't haul a LOT with it (just because of the strain on the transmission) but the 300 paired with a manual transmission and high gear ratio nearly always equals great fuel milage. Especially with the carberated 300's.

The 302 also does real well with a high R&P but not so much. It's a V8, and only being held back with a high gear ratio. All 302's should have come with a 4.56 gear from the factory. They love to rev and make great power doing so.
Unfortunately, the fuel mileage takes a big hit with gears that low - no matter which engine, let alone a V-8.

 

It's the 4wd. It kills mpg's even though it's disengaged, you have all the extra weight, plus you're still turning shafts, and the front diff. 4x4s weren't destined for high mileage.


On another note. My 5.0 with 3.55s used to only get 14 at best. Then I got some bad gas with ended up plugging 2 injectors. So I rebuilt them, and now I can cruise all day at 70mph and get 17mpg easy. Maybe you should run a high concentration of injector cleaner through it. I couldn't hurt.

 

My XLT has a curb weight of 4186 lbs, so it's not a light weight truck. I have the 4R70W tranny with 3.55 gears with the 5.0 V8.
I think that some of the variances of MPGs can be explained by the different curb weights of regular cab vs. XLT and the different gears. I did everything that I could find out to try and improve the MPGs but had no success. If the injectors are clogged, I gotta do something more drastic because I already Seafoamed the engine. I was getting 13~15 MPG before but my last check showed right at 12 MPG
The one thing that might have killed my mileage was that the AC compressor started locking up and you could feel the changes of idle speed. Also, the shop where they tested it (and found it damaged) let it idle for a long time while they checked the AC. Now that the AC is not working, and I'm not letting it idle for 45 minutes or more, maybe my MPGs will go up

 

I changed the O2 sensor the other day and I checked the mileage. Driving stop and go in the city I averaged 14.8 mpg. That seems to be an improvement from before. However, I just drove 70 miles since filling up. I might have to carefully refill the tank and try again to see what happens. I might try to go camping so I'll have at least 160 miles of highway driving.....

 

Ahh.. Nope! On these trucks when 4wd is disengaged all of the front drivetrain is disconnected so it is exactly the same as a 2wd. But yeah all that heavy drive gear is still under there and you have to push it around which will have a negative effect on city fuel consumption. My XLT Ext cab 4x4 with 3.55/30" tire and the 5.0 weighs right at 5000lb and it manages 14-15mpg mixed right now which is pretty good. The 2wd reg cab trucks are at least 1000lbs lighter and that is why they can get good milage with tall gears, put 3.08's in the axles of my truck and fuel milage would go right in the toilet and I'd have to forget the transmission has overdrive because I'd never be able to use it.

 

I have 3.08's in my reg cab 2wd that has been lightend to around 3800#. With my truck in overdrive and crusing at 70-75 it doesn't even think about changing gears crusing over hills and average 17-19 mixed.

 

What are some ways to lighten these trucks in a significant way? I have a '94 XLT extended cab, 6.5' bed. What can I remove that will make a difference? My truck will definitely shift out of OD on some longer uphill sections of the interstate. I have a 3.55 gear but I think there is not enough power to keep it from downshifting some times.

 

Smog, cats, iron manifolds, shorten up exhaust routing, correct size tires and wheels, no extras-running boards, nerf bars, toolboxes, drop in liners, etc. I even removed the spare, jack, etc. Other ways are to lighten would be to replace some of the parts with fiberglas parts and the rear glass with polycarbonate. a

 

i had a truck like yours for awhile. 233k on the clock and i got 20-23 mpg on the highway before i sold her.

my current truck in my sig however is a different story.. 12 if im driving and behaving, 10 if im playing a good bit with my foot in it.

 

I'd be really surprised if it's that light, it's the same truck as mine minus the 4wd components and there's no way that adds up to 814lbs.

 

There isn't enough power.. or more correctly TQ at the rpm range you end up in at those speeds. Longtube headers will help quite a bit but the better solution is a gearing change to 3.73... which may have a negative impact fuel milage of course. The bottom line is 5.0 isn't enough motor for the heavier trucks.. given the transmissions available, a 5-speed auto would improve highway performance while still allowing the use of taller gears, but that isn't an option so there's no sense discussing it. The 5.8 I had in my truck got quite a bit better highway milage than the current 5.0, it was amazing the hills it would climb without dropping out of OD.

 

If it's been run very long with a miss the CAT is probably toast.

 

i average around 16-17 in mixed driving with my 300/4-speed manual. i, too, have heard of people getting 20+ but no matter how i drive, i just can't make my 6-popper get that...even on the freeway. maybe if i drove 55? i usually do 70-75 and keep up with the slower traffic...

 

You are probably right. I just quoted the published specs. Pick up trucks are pretty heavy anyway and this truck of mine is particularly heavy, at least compared to any of the cars I've owned.

And you are also right about the 5.0 not having enough guts to propel that truck