20.5mpg? Something's not right here...

[D-Day]

I know something's not right here, and it annoys me. I filled up on the 29th, and topped off the night of the 30th. I added all my errands I did those days and I can only account for, roughly, 211 miles.

I wrote down I filled up on the 29th at 54,661. Filled up the night of the 30th at 54,986. That's 325 miles. I had to have messed up a number when I wrote something down - that or my odometer is running fast somehow. However, I've done a lot of short runs since then, as well as one today, and it comes up to 54,990. So it seems fairly accurate. I just don't remember where I racked up those other miles.

I filled up my tank the night of the 30th as mentioned, and got 15.8 gallons at $3.93/gallon; total $62.39 The price paid per gallon and how much I bought does add up to 15.8. That's not inaccurate.

Right now I'm going nuts wanting to know if I actually got it. I have attained 16mpg on the highway at 75-80mph+; is it possible that driving at 55mph for long periods of time (most of what was done with my trips in those roughly 30 hours) gave me 4 more mpg? I don't believe it. I can't. I know it's not entirely out of the realm, but not being able to account for those miles, I'm gonna have to chock it up to error and assume I just got around 14-15mpg.

Sucks. Guess I'll never know.

[rfmaster]

Originally Posted by D-Day

I know something's not right here, and it annoys me. I filled up on the 29th, and topped off the night of the 30th. I added all my errands I did those days and I can only account for, roughly, 211 miles.

I wrote down I filled up on the 29th at 54,661. Filled up the night of the 30th at 54,986. That's 325 miles. I had to have messed up a number when I wrote something down - that or my odometer is running fast somehow. However, I've done a lot of short runs since then, as well as one today, and it comes up to 54,990. So it seems fairly accurate. I just don't remember where I racked up those other miles.

I filled up my tank the night of the 30th as mentioned, and got 15.8 gallons at $3.93/gallon; total $62.39 The price paid per gallon and how much I bought does add up to 15.8. That's not inaccurate.

Right now I'm going nuts wanting to know if I actually got it. I have attained 16mpg on the highway at 75-80mph+; is it possible that driving at 55mph for long periods of time (most of what was done with my trips in those roughly 30 hours) gave me 4 more mpg? I don't believe it. I can't. I know it's not entirely out of the realm, but not being able to account for those miles, I'm gonna have to chock it up to error and assume I just got around 14-15mpg.

Sucks. Guess I'll never know.

Get a GPS unit (Garmin, Tom-Tom, etc) They are excellent for calibrating speedos with different tire size, gear ratio.

//RF

[DavesRide]

Yes it does make a difference on how far you push the pedal down. It might just be natures way of telling us all to slow down. I feel confident that you are getting better mileage going slower. I read the other day that some, if not most, get best MPG@42 or so MPH. I have been trying to practice this myself by accelerating slower and stopping slower. My truck is for "use" as a truck and is parked most of the time and I drive the econo VW van back and forth for daily use. In it I can spend $35.00 currently and drive all week long to my "needed" places I.E. kid to school, grocery, old truck hunting, work to and fro twice so I can eat lunch at home, and to the ex's (80 mile round trip once a week). I do pay attention to pedal pressure as it does make a big difference. If you get a VW look me up also on the SAMBA.COM or the VWVORTEX.com. It is working for me to be able to afford it all. My van was $500. and can carry at least 15 4X8 pieces of plywood at the same time all inside. Bash a vw if you want, David. Type in BNWNTA into Google and you will find me there.

[streetstar]

how did this turn into a VW van discussion in just a handful of posts

[impalamark]

litle off topic and a possible hi-jack but reminds mew of
a friend who's father in the 70's gas crunch kept worrying over his gas mileage
so his son would sneak out at night and add some gas to the tank
with out him knowing
was funny till the son fessed up had to wash and wax the car every weekend for two months
Mark

[DavesRide]

No hijack. My truck costs $.70 per mile and I only use it for work. It is true about letting up on the gas pedal. 75-80 MPH? Pay for it. Everyone is doing it. And *****ing about MPG, everyone is doing that also. This gas thing is real and now. Just a suggestion not a hijack. The math thing is not that hard to figure out but is really out of the ordinary. Not from your math but from the price of gas. David

[killthewabbit]

If 20 mpg is wrong, I don't wanna be right.

I bet you just ended up behind a semi or drove easy for that trip and got good MPG. Sounds like you think your odometer is accurate.

[79gmcsierragrande]

Back in the 70s during the gas crunch the “National Speed Limit” was set at 55mph because it was the most fuel efficient higher speed you could go in cars of that time. In the 90s Clinton lifted the National Speed Limit and states were aloud to set them at what ever they wanted. The federal government convinced states to follow the limit by telling them that they would not receive any federal funding for their highways if they did not. Anyways In my truck I can literally watch the gas gage go down at speeds above 55 because the RPMs are so much higher and the 4BBL carb is open full.

[old Rusty C10]

my truck couldnt get 20 mpg if i coasted downhill behind a semi and had my ex wife pushing i cant get better than like ten

[MylilBowTie]

What size tires are you running? I guess 16s but need the tire size like 245/70/16 or something like that.

Then we can figure out the speedometer gears you need. It may not be that far off but you may never know until its checked.

That's a good idea to barrow a gps if you can. It will help to show if the speedometer is off. I would find a long level road and set the curse. Last I knew about gps is takes a few seconds to relay the actual speed. So you will want to drive at a steady pace.

If your speedometer is off it will be more inaccurate the faster you go.

I need to change the speedometer gears in mine. I got a th350 that has who knows what speedometer gears. I also put 33s on the rear with the 3.42 gear its pretty close.

[D13]

Best fuel mileage with a non-overdrive truck is 45mph. stepping up from 68 to 72mpph costs 1mpg on my truck. Running 80 drops 4mpg, particularly on the square bodies.

You don't say what powertrain you have but my 4.3/700R4/3.08 got 23mpg and my 5.3/4l80e/3.43 ext cab 3/4 ton gets 17mpg, same as my 250/3on tree/3.43 3/4 ton.

[Ivan D.]

D-Day, yes tis entirely possible you got that much, I've seen 20mpg from my old '79 short stepper on several occasions - just gotta figure out where the sweet spot for the engine is, my 350 just loved 1/4 throttle at 2000rpms, which with the 33s and 3.08 gears in the rear ended up at right about 60mph in 3rd. Anything over 2500rpms would make for very lousy fuel economy, cause a) the engine was out of its best efficiency range, and b) air drag increases exponentially with speed. By driving slower you reduce both engine speed and air drag, and that can go a long way for the mpg thing.

[D-Day]

It just kind of blows my mind.

As for my truck, it has 245/70/16 tires, 3.73 gears, 700R4, 400 V8 and Edelbrock carb/manifold, Mallory distributor. It's 1973 C2500 crew cab.

It's good to know my truck can get that many miles a gallon; just needless to say I'm a little stunned it's possible.

My speedometer should be accurate, but I will check it anyway. I have two GPS devices. For over 2 years, I actually used one of them primarily as my speedometer because I couldn't trust the gauges. Kept me from getting speeding tickets. Then after I got my new transmission and correct speedo gear for the time I stopped using it.

[Greenlee]

20 mpg is a little surprising, but I can believe it. I have 1976 Silverado with 350 and 700r4, and I have a 2006 Nissan Titan Crew Crab. I get about the same, if not better, mpg with my old truck. You would think after 30 years the new trucks would do better than that.

[MylilBowTie]

You will need a Drive gear of 15 (gray) and driven of 38 (blue). That is the closest setup I could find using what you have.

[1LoC10]

driving 55 on the expressway will def help out alot
I get 15MPG in my crew cab around town driving
but i drive 100 miles a day to work and back on the expressway with cruise at 65MPH and i get 20MPG, and its a big heavy truck

[D-Day]

Nice truck.

Good to know it's possible with my truck. Now...can I restrain myself from driving faster all the time? Not likely; not now anyway. Maybe in time when I need to get somewhere on low cash.