Cummins 4BT & Diesel Conversions Forums banner

1 - 5 of 5 Posts

·
Registered
Joined
·
84 Posts
Discussion Starter #1
I tested the mileage for the first time in my 1989 f150 2wd 4bt on Sunday. I traveled 135 miles. I used 30 pounds of fuel. From what I could find online diesel fuel weighs about 7 pounds per gallon. If that equals 4.28 gallons I made 31.5 MPG.

My f150 has 3.08 gears with a four speed non overdrive transmission. My tires are 235 35 15 and measure about 28 inches across. I traveled almost all highway miles going right around 55 mph. The online calculator puts my RPMS at 2032. Sunday was a near windless day and I was traveling on level ground. I drive like an old man accalerating slowly and planning my stops far ahead of time. I filled my tank completely full with a 5 gallon gas can before I started. After my trip I filled tha gas can, weighed it, (on a bathroom scale) poured most of it into my tank, and weighed it again. I did check my speedometer with another vehicle before I did the swap.

I am pretty confident with my results. I think the biggest wildcard was the bathroom scale but I'm guessing it had to be pretty close. I do plan to switch to an overdrive transmission in the future. Probabally the m5r2.
Please let me know if you see any flaws in my test.

Regards

Cornfeed
 

·
Registered
Joined
·
126 Posts
Cornfeed, that is great news, since I believe your mileage
is going to be even better with refinement of those things
you've mentioned. In the conditions you describe I am willing
to bet your low-load mpg will be best just below the max
torque (max is approx 1800).

As for the bathroom scale, most of those read accurate in the
middle of their range, and they read pretty poorly at the ends.
For example, if the scale has a range of 0 to 300, the best
measurements will be around 150, and poor measurements
will be at 0 to 30 and 270 to 300. So next time maybe have
enough pre-set weight on the scale to total around 150.

(some digital bathroom scales have better readings across the
full range but most don't, it's just the mechanical nature of
the workings inside.)

Keep the reports coming, I am learning a lot here!!!:)
 

·
Registered
Joined
·
696 Posts
Very unusual way of figuring mpg, is there any particular reason for weighing your fuel?. To get a more accurate figure I would fill er up drive till its empty and then fill back up to same point. There are variables in this method also, time of day affects temp of fuel and therefore its density. Fill up 1st thing in the morning and you will get a little more fuel for your money. Then average your fill ups over a month or so and this will give you a fair idea of your mpg. I think this has been covered before.

Gaza
 

·
Registered
Joined
·
2 Posts
Cornfeed,

I'm very excited to hear of your progress as its very similar to one I want to do.

I have an 86 Dodge D150 2wd with a 318, 3 speed and positraction. I'm looking for milaege and towing capabilities.

Do you plan on towing with your rig?
 

·
Registered
Joined
·
84 Posts
Discussion Starter #5
I like your idea on the bathroom scale. I still had the jug with about a gallon of fuel left in it, so I hopped on the scale holding the jug and compared it to just me on the scale. I did come up with the same figure (8 pounds) that I used in my original test. The reason I am weighing my fuel is because I don't trust the flow meter on the tank I am pulling from. For my next test I will run the tank closer to empty. I just completed my swap so I wanted to get an estimated fuel economy right away.
I do not plan on towing with this rig. I have a ford f700 and a semi for that. I may end up putting a slide-in camper on someday though.

Regards

Cornfeed
 
1 - 5 of 5 Posts
Top