Just filled up the truck (1980 F-150 Ranger XLT supercab- 351M engine-110,000 miles) last night as word was out that prices were going up to $1.16/litre ($4.15/gallon). I calculate my gas mileage at each fill up and it's down to 10.5 mpg. Not good in my estimation. I know that she could use a new carb, or at least a rebuild. I replaced plugs, cap and rotor, but not wires yet. Haven't checked the timing on it yet, either. The choke seems to be working as expected. But with that, I'm wondering what else I can do to improve the gas mileage on this otherwise nice truck. Our hard Labrador winter is coming and I'm guessing the mileage will go down to 7 - 8 mpg. All vehicles do much worse here in the winter as it gets so cold and we don't have much road to travel on at all. Any advice is appreciated.

 

A messed up carb will get you bad gas milage faster than anything..

 

Rebuild the carb and get new plug wires. Both will help improve how it runs and should
help mileage.

 

Are you running larger than stock tires? That can affect mileage. Also your driving habits make a difference too. If you drive it easy, you'll get more mileage than you would if you're mashing the pedal all the time.

Believe me, I learned that last one the hard way. lol

 

Some simple, yet often overlooked things are (1) tire air pressure [especially as temperature drops so does the air pressure, causing increased rolling resistance], (2) you mentioned timing - is your vacuum advance working?, (3) do you have pre-heat to your air intake?, (4) seasonal adjustments to the choke are often required [if the choke stays on longer than required, it will adversely affect mileage, (5) is your thermostat functioning and of the correct temperature? (6) is the air filter element clean? (7) are your brakes dragging? (8) is your alignment good? (9) are you using the lightest weight oil recommended for your application? (10) are you carrying any unnecessary weight in the truck?

 

Thanks for the replies. The carb rebuild right now is the last thing I'm able to do. No one does it around here and I'm not confident right now to tear it down. I did adjust the carb to lean it out a bit. The tailpipe doesn't seem as black. My tires are stock size. I just installed a preheater hose to my air intake yesterday, so I'll see if that improves the mileage. Haven't yet checked the choke adjustment. I should install a manual choke, eh? I'm going to install a new 190 degree thermostat. The heat right now is good and the engine and hoses warm up well. The temp gauge registers on the cold side even when the engine is warmed up good. I should track down to where the sensor is and consider replacing that. I have a new air filter, but I hear that K & N filters are best (?). I still need to check the ignition timing. I have a very light foot and am teaching my son to drive the same. All new brakes on the front with no sign of drag, nor in the rear. Front end recently aligned. No exta eight in the truck at all. Mind you, our driving here is strictly "city."
Is there any benefit in bypassing any vacuum lines?

 

If you're serious about increasing fuel mileage add a vacuum gauge and use it. When accelerating or cruising focus on keeping the engine vacuum as high as you can and still maintain the speed you want. You'd be surprised how easy it is to "over fuel" an engine and using the gauge will "lighten your foot". If you don't get a mileage increase I'd be very surprised.

Also keep in mind that wind drag increases exponentionally as speed increases ... less speed, less drag, better fuel efficiency.

Without excessive winds I run ~7.5 towing my 10,000# fifth wheel.

Good luck with it.