fuel mileage

[96OBS]

Hey guys, I feel like I'm not getting that great of fuel mileage. I have the dual 15 gallon tanks but only use the front because the back one has a hole in it. I think I'm just used to my old Cummins with the one 25-30 gallon tank getting about 450miles to a tank. But in the city I'm only seeing 100-150 miles to half a tank. Idk if that's good or not. I normally don't fill it up I just put $20 in here and there. I filled it completely full once on a 4 hr trip on the interstate cruising at about 65 mph at 2000rpm and I got 242 miles to half a tank. Then I drove in the city with the other half of the tank and got about 150 miles out of it. I drive it easy just about all the time. Shift at 2000 rpm. Sometimes I'll go to 2500 rpm just to hear her roar. But not that often. Does anyone know how I can calculate my mileage?

 

[POWER-STRUCK]

(1)fill it up, (2) reset trip meter (3) drive it (4) fill it up again and document how many gallons to fill it up (5) miles driven divided by how many gallons =MPG

 

[96OBS]

Okay man thanks. I'll try it out!

 

[stroker2]

(1)fill it up, (2) reset trip meter (3) drive it (4) fill it up again and document how many gallons to fill it up (5) miles driven divided by how many gallons =MPG

:whs: But if that doesnt work, install the super duty overhead console and it will tell you your mileage.....

 

[Bugman]

If you have a regular cab with a aftermarket flat bed the tanks are not 15 gallon but 19 front and a 18 in the rear. On my truck I have put 21 gallons in the front and 19 in the rear.

I agree that you can not go by the guage to see what kind of mileage that you are getting. If that was correct then I could get 100 mpg on the front and less than 2 on the rear.

The only way to do it correctly is to do the math over several tanks of fuel.

 

[96OBS]

Well I put the flatbed on myself, i bought it originally with a bed on it and it was rusted so I put a flatbed on it.. So I'm not sure. Its the stock tanks that came on it from factory. So I was just guessing 15 since it had dual tanks. But let's say it is 15 gallons, I know I can get at least 300 out of a full tank divided by 15 is like 21... it just don't feel like I'm getting 21 mpg if I did my math correct.

 

[08straightpiped]

It would be 20mpg and I would be real happy with that

 

[Bugman]

The stock factory tanks were 19 front and 18 rear. They didn't put a 15 gallon tank in a long bed.

Also as I said you can not go by what the guage is saying. I can go 100+ miles on my front tank with the needle not moving but when it hits E in is empty. Likewise on the rear. It will come off of full by the time I pull out of the filling station but I can go a long ways when it hits the E.

That is why you need to do the math. Fill the tank and record the miles. Then when you refill your tank take the miles driven and divide the gallons used into it. That way there is no gessing.

 

[96OBS]

Okay I'll try not to run it out but I'll go to E and see what it says.

 

[Redpower]

FYI- on both of my obs trucks E is empty - out of fuel.
On my 97 F-350 auto with 4:10 rear I might get 15 mpg empty.
My 95 F-250 auto with 3:55 rear, I usually get 15-17mpg on shorter trips.
I think 20 mpg would be tough to get unless you got the gears and open road.

 

[Bugman]

You don't need to run the tanks empty but you need to fill the tanks and do the math if you want to know what the mileage is. If you fill the tank when it hits E and it only takes 10 gallons then you know that the guage is off. You just have to be aware of what the tank actually holds and not just guess.

 

[96OBS]

Ya I had to put a little in today, I didn't have the most ey to fill it up all the way so I'll have to wait to try. I'm thinking more around 15 mpg with a 19 gallon tank.

 

[Aljay]

Best I have seen is 21 with mixed city and highway 4.10 gears and 285/75/16 .

 

[96OBS]

Well I still Ned to get it close to empty to fill it all the way up. Plus I added about 800lbs with the flatbed and I'm running 305/70/16....

 

[jschildm]

It doesn't matter how empty you run it. Fill it up. Write down the miles. Drive it. If you can't fill it all the way up, just keep the receipt so you know how many gallons you put in. When you do fill it all the way up:

(Current mileage - Beginning Mileage)/Total gallons added over that time.

The longer you keep track, the more accurate the number will be.

 

[Petro]

What I want to know, is how does someone not know how to calculate their fuel mileage? Your typical twelve year old should be able to handle the simple math required to figure that out.

 

[96OBS]

Well sorry but at the moment I wasn't thinking...... but I'll just fill it up when I get the money and go from there, thanks....

 

[Kritter]

Be happy with 20 I'm getting 16-18 mpg. I'm also running 4:11's and auto trans.

 

[96OBS]

I don't think its 20. If its a 19 gallon tank then I'm getting 15

 

[OldschoolPSD]

Mine is doing 15.9 right now with 33x12.50's and 3.55's but I have a short in my wiring harness somewhere that is making it act a little funny. That is with the current setup though.

Best I have seen is 21mpg on stage one injectors with 285's pumped up hard all highway.

My 1st gen cummins would do 22mpg on 35" tires with 6" of lift under about any conditions. Around town, loaded, unloaded, didnt really matter. It did 21mpg on a trip to MI with me jamming a stick against the accelerator petal and running 85-90 against the governer the whole way. Redneck cruise control.