I posted this in the 1980-1986 forum and thought some here might be interested.


https://www.ford-trucks.com/forums/1...-9l-300-a.html

 

That was a good read and impressive to hear about your experimentation. A lot of people put rear spoilers on their cars with no positive effect, but in many cases a chin spoiler will improve fuel economy (like you found) and will improve front end grip. Nice find!

 

Thanks for the input, mefast!

 

A bed cover has been alleged to help with MPG. Something that is routinely overlooked by many is keeping the tires pumped-up to maximum recommended pressure.

 

Thanks, Harte3!


For the trip, I did bump up the air pressure a little. Normally [unloaded], I run 35 psi in the fronts and 32 psi in the rears. I looked on the sidewall and the maximum is supposed to be 35 psi. I increased the fronts to 38 and the rears to 35 psi.

 

Bed cover gained me at least 1.5 mpg. Looks pretty sweet too. Don't quote me here but from my understanding increasing the rear wheel pressure essentially increases the tire diameter. Which will increase mpg but will show a decrease in your stats due to a slightly off odometer. Not sure if 2 to 3 lbs of extra pressure is enough to throw it off much but that is what a much wiser gear head explained to me. I do say with certainty , yes to the bedcover. I have also thought about somehow eliminating the parachutes under the body/ rear wheel wells / bumper, with dams or leveling the transitions with sheet aluminum or some other rigid material. In an effort to decrease under body drag. I think it can be done without being noticeable from eye level without looking like an eco-modder. Been threatening to try this for years.

 

The high-MPG models in the early 80s came with "extra Load" tires...which showed a max of 41 psi, and I believe I recall Ford calling for that pressure.

 

Here's a funny thing, proving that intuition doesn't always translate to real-life improvements (nor do ostensibly-"scientific" software programs, for that matter). Some testing outfit, and I think it might have been Consumer Reports, tested fuel consumption of various models of pickup trucks, first with the tailgate up (and no bed-cover), then with the tailgate down, which is popularly thought to improve mpg. Well, some trucks did a little better with the tailgate up, some did so with it down, and some showed no significant difference either way, and it was impossible to predict which would do which, lacking a wind-tunnel. This was done maybe ten or so years ago, IIRC.

Here's another example: Way back in the days of the Mobilgas Economy Run, we learned that the pro and semi-pro teams that took part in the Run always pumped the tire pressure way up. Ah, but sometimes that made things worse! What they found happening was that the hard, skinny, over-inflated tires could sometimes vibrate the carburetor float in such a way that the float needle got to bouncing open and closed, raising the fuel level in the bowl at least enough to richen the mixture and sometimes enough to spill over. Well dang!!

And the trouble is that for any ordinary vehicle owner to set up accurate, repeatable road-tests is not at all easy. Having good instrumentation, such as a fuel flowmeter and a relative air density meter and correction table, would help a lot.