I have a ford dumptruck that has been getting 5 mpg hauling firewood on one ofe my jobs. 90 mile round trip. leaving for work temps outside have been 17 degrees in the morning, 30 degrees in the evening . I am hauling the same weight load, driving the same speed , same route. I fill up at the same pump every evening. 18 gallons, 5 mpg. today, on the way home, I inadvertantly left my manuel choke on , didn't notice it til about 5 miles from home. truck seemed to run fine, no loss of power, but when I filled up, it only took 16 gallons! 5.6 mgp. do I need to richen up my carb?
Might want to look into the vacuum-operated emissions gadgets that may be under the hood (what year is it?)...make sure they're all operating and adjusted. Also ignition timing...if it's too far advanced and you can't hear the knock then it might behave as described.
it is a 74 with a 477 superduty. no smog. when I installed the carb, I had to turn the idle mixture screws out 3.5 turns to eliminate hesitation off idle. the truck seems to run fine. on a rig like this more power means better mpg. I am doing mountain driving, and the longer I am on a hill, the more gas is used. if slightly richening would give me more power, I would expect better mpg. it is a very low compression engion. timing doesn't seem to cause pinging. right now I have it advanced enough that it backfires going down hill
this carburetor came off a smogged bronco. I don't know what year. I assume it was set up lean for emissions. going up 1 or 2 jet sizes might be worth a try. just using the dumptruck gives me 5 mpg, but when I am pulling my backhoe mileage drops to 3 mpg. the compression on these engines is 7.5:1 so a turbo would be nice, though a blower would be easier. like I said before, more power on the hills means less time on the hill, which equates to better mpg.