MPG woes

[tev123]

I searched the class b forum for mpg related topics and found/read a bunch.

First far trip on my class-B,
1990 Ford Econoline 250 Intervec Falcon with Ford's 5.8L windsor V8

No check engine lights, passes emissions, recently replaced a few cracked hoses around throttle body and a bad throttle position sensor. No bad ECU codes either.

Did a 135 mile round trip and used up 15 gallons, thus 9 MPG!!!
90% highway at around 60mph. Light wind.
Not carrying anything externally other than what came with the van (roof top/ac) and 2 solar panels that lay pretty flat (about 1" gap between roof and panel)
Tire psi at 60 front/80 rear.

Is this normal/avg? anything substantial I can do to improve MPG?

Thanks!

[mkguitar]

alot of apples and oranges-

The vehicle referenced shows the inferior fuel mixing, spark timing and motor controls of the older vehicle.

could just need a tune up- plugs and wires, timing and dwell- carb adjustments and checks for vacuum leaks.
the catalytic convertor could be clogged- a more open exhaust can often help mpg but make for a droning ride.

mike

[DandD2015]

Our Chinook Concourse (dually, Triton V10) gets 10 mpg very consistently. If we hit 9 mpg, the next tank will probably be 11 mpg. I drive maybe 3-5 above speed limit on highway, very little running of the generator. Considering what these things weigh, that's not bad. I once had a 1976 Pontiac Catalina that only got 9-10 mpg.

[ernie1]

I had a 1989 Falcon 190 on a Ford E350 chassis with a 460 ci engine that was fuel injected and I got about the same mileage as you do while doing 65-70 mph. It had a 4.56-1 rear end ratio and the engine was always revving while going down the highway. I think you need to do a few more trips to ascertain a true average mileage but you might be doing okay as far as gas mileage goes.

[tev123]

thanks everyone for the suggestions, ideas, comments

[topless]

3 things affect mileage the most: aerodynamics, speed and gearing.

You can't do anything about the aerodynamics. Most trucks built back then were designed to run at the 55mph speed limit. However, engine speed will drastically affect fuel consumption.
Too slow causes lugging the motor, too fast puts the engine past peak power. Both conditions use fuel.
See if you can find out the rear gear ratio. It's possible the truck was built with a numerically low rear axle ratio, like 2:52 - 2:73. If so, the engine at 60 mph is running way too slow to use it's power and lugging the motor. That runs the throttle more open to keep speed up.
There are online calculators that will convert engine rpm, vehicle speed with tire size and give you the gear ratio.
For a heavy vehicle will poor aerodynamics a better ratio would be in the 3:30-3:50 range.

[pasusan]

It sounds a bit low to me.

We have the same engine, only with a carburetor and no computer. We get 8.4 towing, which according to others here is reasonable. Not towing it was somewhere around 14 - I checked years ago and never wanted to check again. 😮 We do travel at whatever the speed limit is though - no slowing down...

[schlep1967]

Might try a bug deflector on the front of the hood. It may direct the air up over the top a little more efficiently.

[Happy_Camper3]

a friend of mine used to have a 1991,looked exact same as yours. got 14.3 mpg averaged over 1200 mile round trip. for what its worth.

[RoyB]

The wind drag is what does you in...

[midnightsadie]

had 1998 looked almost like yours ,got 14teen all day long. we don,t drive over 65 mph. my 2007 LTV only gets 20mpg its a mercedes benz 5cyc diesel.

[Sandia_Man]

Other than driving slower there is not a whole lot you can do to vastly improve mpg. We tow our 32' TT and average about 8 mpg if we don't go over 65mph, unfortunately we tend to go a bit faster on the instates out here in the West. I stopped fretting about mpg early on when we starting RVing over a decade ago knowing it is just part of the cost to enjoy this lifestyle. Haven't recorded mpg on a trip in over ten years.

[LadyRVer]

I had a PW, it averaged 12-14 on the highway, normally 55-60 mph. Mine did not have the high top your picture shows. Around town was about 9-10. I agree with the statement, do about 3 fillups, average the 3. Also, if you were running generator, that figures into it

[dave17352]

That mpg doesn't surprise me. For the year and the rig. If your willing to travel at 50 mph you will probably gain a couple mpg.

[Jayco-noslide]

Sounds bad. I get about that + or - 2 with our 30 ft. Class C V-10. But before you give up realize that the way we check MPG isn't real accurate and 1 short trip isn't enough to get close to a true reading. But, if you can't get 12 or 15, I guess why have a Class B?