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!

[tev123]

Updates: have taken several 130 mile trips and MPG is averaging 10.5mpg, driving about 80 percent hwy at 60-65mph, light elevation changes

[tev123]

ffjeff wrote:
Are you sure your speedo is calibrated to the diameter or the tires your using.

speedo is fine; waze app shows gps speed which is within +/-1 of speedo

[ffjeff]

Are you sure your speedo is calibrated to the diameter or the tires your using.

[tev123]

DenDanger wrote:
I think '90 might be fuel injected. I know the 302 was in '88 but also seem to recall Ford made a 4 bbl version of the 351 quite late so could be?

But good points and I guess I should add for comparison the 318 in the Dodge is fuel injected and has a 3 spd auto. (No idea which one, 904? 727?)

it's fuel injected with separate injectors per cylinder and fuel rail (not throttle body injected)

[tev123]

Updates:

after research and help from this forum, I bought a fuel pressure test kit as most people having similar symptoms on this engine (ford 5.8 windsor) suggest the fuel pressure regulator, fuel filter, or fuel pump;

tested the fuel pressure and it read round 70 psi!!!!, bounced all over the place with the engine running, leaked down to 0 with the engine off.

replaced the fuel pressure regulator ($20 part) and it is a steady 38 psi, engine on or off, and no leak down either, so this may have been the culprit. I have not taken it for a ride yet as I am also upgrading the spark plugs, wires, distributor cap/rotor, and coil. will check the timing while at it too.

will report back once I do a trip worthy of mpg check.

[Airstreamer67]

If you have a catalytic converter I'd recommend you take a look at it.

[tev123]

New info:
just did an 810 mile round trip, with about 1/2 of it mountain elevation changes (Southern NH -> Quebec City -> Montreal -> Southern NH)

- just computed my MPG to 7.4!!! given all the gallons/liters I used
- avg speed around 53
- tires at 80 psi rear / 60 front
- struggled to go up hill slows down to 40 unless I remove the overdrive/kick in down a gear
- normally kept it at 55mph most of the time, 65 down hill, 50 up hill...
- engine temp reached Hot several times while going up hill / kicked down off of OD;
- feels as if it lacks power when the pedal is down all the way (as if the intake is collapsing or it cannot breath - big engine noise, but drives slow)
- check engine light came on / off several times, specially after going up hill and pedal down...

I will be checking engine codes later, timing, plugs/wires, dist. cap, etc;
I used 87 octane gas.

For some of the other comments/questions:
engine is a 5.8L (351cu.in.) for windsor
new throttle position sensor, new oxygen sensor, new air fitler housing, new air filter
transmission is 3+OD; (or is it 4+OD?)
stock wheels (16")
everything is stock

[lucytravel12]

I drove an '87 Dodge Falcon and consistently got about 11 mpg. Usually drove 55 - 60 mph. Be sure to check your tires.
Ditto the earlier post - it the freedom of driving a B that gives the best reward!

[lucytravel12]

I drove an '87 Dodge Falcon and consistently got about 11 mpg. Usually drove 55 - 60 mph. Be sure to check your tires.
Ditto the earlier post - it the freedom of driving a B that gives the best reward!

[DenDanger]

I think '90 might be fuel injected. I know the 302 was in '88 but also seem to recall Ford made a 4 bbl version of the 351 quite late so could be?

But good points and I guess I should add for comparison the 318 in the Dodge is fuel injected and has a 3 spd auto. (No idea which one, 904? 727?)

[omjones]

I think that he has a C3 trans. 1990 went to a 4OD which was the 4 speed overdrive. Also if it's a carb he's probably doing ok at those numbers. I've had an 88 and a 90 and the difference was dramatic with those factory upgrades. My 99 is much better yet.
john 'I am Canadian'

[DenDanger]

He said he has a 5.8 (351) and the Dodge has the 318 so I'd think if anything the Ford would be a bit better since the Dodge is slightly underpowered. My Uncle has an '88 Ford with the 302 and although I think it's actually lighter than my Dodge I think it is worse for gas mileage. Thing is though, I've never done the numbers on his Ford.

Either way, I felt the Dodge was close enough in general to get a ballpark as it seems no one else has any numbers that closer reflect his unit.

Of course the higher speeds could also be a factor.

Cheers all!!

[cbigham]

The Dodge probably has a 360 in it not a 460. You may be able to redo the gearing in back. A 460 is an earlier version of a towing motor like a v10 .

[DenDanger]

It seems a little low to me but not by much.

I have a 1989 Dodge B250 with a similar top. I did take the rooftop A/C off this past winter as I found it was really catching the wind badly in a storm but so far mpg is about the same as last year.

It'll get anywhere from 10 1/2 to 13 mpg in mixed driving as I use it quite regularly as a daily driver. I know the lowest was during the winter at as low as 7 mpg in January but can't count that as it's irrelevant to your driving.

So far this summer it's been getting 10 1/2 to 11 1/2 and though a lot of in town we are in a small village in a rural area so fairly long runs. I do fine that dropping the cruise from about 100 km/h (62 mph) to the 85 km/h (just about 50 mph) will make a 2 mpg difference. Tanks where I've done a lot of back roads and steady at the slower speed will return closer to 13 mpg although I only fill up about once a month so still getting a handle on this summer's mpg.

This may not help a lot but since it is real world driving and I keep track of mpg (U.S.) to the 100th of an mpg I thought I'd throw it on here.

Cheers.