Okay, I've calmed down from the power outage … continuing on fuel economy ...
But first, an old school technique for teaching economical driving was to place a cowbell upright on the floor. (Good luck finding one nowadays.) If the bell clanged (or fell over), it meant you'd accelerated, braked, or turned too fast. (Flying up off the floor meant a bumpy road, in case you hadn't noticed.)
Next up is replacing the air filter element. A dirty, clogged air filter means the engine has to work harder to draw air into the carburetor (or throttle body). This means the engine is expending power that could be sent to the rear wheels instead.
Do you have an open air cleaner (possibly from a previous owner), like the one in the following picture? If so, throw it away. (Or give or sell it to someone else.) Replace it with an OEM-style closed air cleaner with a snorkel tube.
These air cleaners are really only appropriate in large, relatively open engine compartments, preferably without a hood. The carburetor on your motorhome's engine is up in a hot, enclosed doghouse.
For efficiency (i.e., good fuel economy), your engine needs dense, cool air. The air inside your doghouse is hot and thin. The air cleaner snorkel allows the engine to draw in denser, cooler air. (That's why most newer vehicles have cold air intake systems.)
Aside from the engine intake needs, the hot environment inside your dog house is detrimental to engine performance. That's why I recommend one or two small marine bilge blowers, like the one below, and dryer vent hose to ventilate the doghouse. (Highway speeds and the engine fan don't really do much to displace the hot air in the doghouse.)
If you want to get fancy, you can use a bilge blower to (mildly) supercharge your engine, which will make it even more efficient. Just attach the blower output to the air cleaner.
Ideally, the air cleaner should be attached to the blower intake and the blower output attached to the carburetor neck. However, that's likely more involved than what most of you are willing to do. So the preceding is sufficient.
Next is to take a look at the inside of your tailpipe. It should have a white or light grey deposit inside it. Dark grey or black soot indicates a too-rich fuel mixture and wasted fuel. Black smoke coming out of the tailpipe is a sure indication of too much fuel being dumped into the engine. Likely causes are too large jets, bent or broke metering rods, or defective carburetor float.
(Blue smoke indicates oil consumption, usually due to defective valve stem seals, worn piston rings, or worn cylinder walls. Older Dodge OHV engines are notorious for disintegrated valve stem seals, which is the most likely cause of oil consumption. These can be replace without removing the heads -- google replacement procedures or ask me.)
If your engine has a four barrel carburetor, try to avoid using the secondary barrels. During normal operation, the secondaries are closed and the engine relies on the primary barrels for fuel-air mixture. Under brief heavy load, such as climbing a steep hill, the secondaries will open to supply extra fuel to the engine. This is normal and the intended, acceptable use of the secondaries.
Tromping on or flooring the accelerator and hard acceleration will also cause the secondaries to open. More often than not, this is simply a case of the loose nut behind the steering wheel wasting fuel. Steady, slow pressure on the accelerator will usually keep the secondaries from opening. (If they do open, it'll just be briefly before closing again.)
It should take 2-4 seconds to press the accelerator from idle to medium acceleration … continuing to wide-open acceleration will also cause the secondaries to open and waste fuel.
If the secondaries do open, they should close when you reach cruising speed and back off the accelerator. If they don't , it means your carburetor linkage is gummed up and you're wasting a lot of fuel. Cleaning the linkage with spray carburetor cleaner and re-lubing with graphite should solve the problem. If not, you probably have bent linkage or a seized butterfly valve shaft.
Hard braking for stoplights and stop signs also wastes fuel, although that might seem counter-intuitive. Anticipating stoplights and stop signs, and letting up on the throttle, saves fuel. Otherwise, you expending fuel maintaining speed before braking hard to lose momentum. (Easy on and off the brakes when approaching stops decreases momentum while preventing brake overheating and excess brake shoe/pad wear … and saves fuel because your foot is on the brake pedal rather than the accelerator.)
(On manual transmission vehicles, I often get stopped by cops for a brake-light check. This is because I use anticipation and downshifting to slow the vehicle, rather than the brakes. Quite often, I don't even have to use the brakes to come to a complete stop.)
People who keep one foot on the accelerator and the other on the brake pedal obviously have money to burn. It wastes fuel by making the engine work harder to overcome the (slight) brake friction. It also causes brake overheating and premature wear on the brake shoes/pads. (I watched one lady I was following do this for over ten miles -- her brake lights were even on while she was accelerating up a steep hill. She very well could have found she had no brakes, due to overheating, if she actually had to stop.)
Next up is more expensive modifications to improve fuel economy.
