MPG calculator versus hand calculations

[P40hawk]

I purchased my '14 power wagon new and have kept track of my fuel usage for the past three years, (Starting in '15). I have noticed a difference between the MPG calculator on the truck and the hand calculations at the pump. Without looking at the algorithm RAM has in the software I can only speculate as to what the difference may be. On the truck, I have never seen the instantaneous calculation go negative when I accelerate which I know it would, so that leads me to think they are using the absolute valve. The software may also negate idle MPG? Anyway, I thought I would share this with you guys and see if you are similar.
The first year I had the truck ('14) was the best MPG. It was 12.4 MPG hand calculated. unfortunately, I did not start keeping the records until '15. MPG has steadily dropped since new. As you can see, I do not drive my truck that much. It is currently at 16,200 miles.

[FordyceCreekTrail]

It definitely calculates Idle in. Noticed that big time yesterday when I finally got around to doing the initial cable re-spool. Lost like .3 sitting idling while I worked. Seems low to me. I have a new engine still and can average over 12 around town, and just at 14 hwy and thats with mountains and living off-road. If I cruised across Kansas I would be looking for as close to 16 as I could get. Of course that would not happen as I would be cruising at 125MPH to get across.....

[P40hawk]

All of my driving is in town. Wife and I have taken a few trips, but none in '17. Planning a Colorado trip this summer. I'm anxious to see the MPG go up with hwy driving.
Have you taken possession of your '18 yet? Lets see it. You'll like the whiteKnuckle sliders. I have them on mine. First thing I ordered.

[nts007]

Keep in mind that as your truck gets older it gets heavier. I know I know what's that supposed to mean. Well pretty easy to fill a trucks cubbies with 40-50lbs of gear, change, cups, boots or shoes, tools, sliders, tool box. A bed liner would add 10-20 lbs maybe. Even dirt can add 10-50 lbs. hell a romp thorough a muddy area can add 100lns. Bigger tires. It all adds up. Enough you can eventually see a reduction in mileage overall. Weight hurts a gas truck more than a diesel. Or maybe you did an exhaust and you like the sound of it hahah.

[OffroadTreks]

So weird that some people get great mileage and others terrible. There are plenty of us, myself included averaging 14mpg with 37's living in a mountainous area. Hell I just drove from Boise to Portland and got around 15.2 after I added my receipts up.

[Chubbs]

My wife consistently gets about 20% worse mileage than I do for any given vehicle. I have given up being concerned about it.

[olyelr]

I have compared the computer readout to hand calculations at every fill up with my new work truck (‘17 Ram 1500 with hemi). It was dead on once, the rest of the time the computer has read anywhere from .5-1 mpg more than the actual hand calculation shows.

As far as my Power Wagon, if I can muster 14mpg out of a tank I am doing good. Usually more around 12.5 or 13. That is normal country driving though, no highways/freeways etc. With the travel trailer hooked up I havnt seen much better than 9 mpg

[olyelr]

My wife consistently gets about 20% worse mileage than I do for any given vehicle. I have given up being concerned about it.

That is a very good point, too. Driving technique is a huge part of the overall mpg calculation. One person could take the same road, with the same vehicle, and go about the same speed and still get quite a different overall average just from the way they are driving.

Wind makes a huge difference too.

[FordyceCreekTrail]

I posted pictures in the photo string. I have the sliders sitting in my garage. Those will probably kill .5MPG due to weight. Want to do some synthetic line to help off set a portion of that weight.

[olyelr]

I posted pictures in the photo string. I have the sliders sitting in my garage. Those will probably kill .5MPG due to weight. Want to do some synthetic line to help off set a portion of that weight.

A very small portion hahahahahah. The sliders on mine were about 290 pounds together if I remember correctly.

[Reloaderguy]

So weird that some people get great mileage and others terrible. There are plenty of us, myself included averaging 14mpg with 37's living in a mountainous area. Hell I just drove from Boise to Portland and got around 15.2 after I added my receipts up.

There is almost no relevant data in any of these threads. I data logged about 70k miles this year and can tell you exactly where my mileage is peak and where it started to suffer. I have a lot less miles in the PW but I can still tell you. On the highway, if I drive 55mph I get roughly 15mpg (15.5MPG on the computer). At 80mph I get about 11.5MPG. This is in optimal conditions. If I drive westbound on I84 in the gorge into the wind my mileage drops 2mpg to 3mpg. Up hill or down hill almost doesn't matter as long as I stay within those speed ranges. Stop and go traffic under 50MPH I get about 9MPG and less if I floor it from stops.

[Ducky's Dad]

I used to hand calc mileage on my '05, but quit doing it after the first few years because the computer and the hand calcs averaged out over time. Saw minor differences on any given tank because of driving conditions (idling, heavy traffic, big load, air temp, ethanol blend vs real gas, etc.). In the end it's all the same on mine.

[P40hawk]

I have compared the computer readout to hand calculations at every fill up with my new work truck (‘17 Ram 1500 with hemi). It was dead on once, the rest of the time the computer has read anywhere from .5-1 mpg more than the actual hand calculation shows.

As far as my Power Wagon, if I can muster 14mpg out of a tank I am doing good. Usually more around 12.5 or 13. That is normal country driving though, no highways/freeways etc. With the travel trailer hooked up I havnt seen much better than 9 mpg

I've noticed the same. I have not had the computer read the same as the hand calculations, and my results are the same as yours. What bothers me, and maybe I'm just weird, but the instantaneous MPG will never go negative even with my heavy foot.

[KevinABQ]

I posted pictures in the photo string. I have the sliders sitting in my garage. Those will probably kill .5MPG due to weight. Want to do some synthetic line to help off set a portion of that weight.

Master Pull has a sale on their 7/16th superline synthetic (36.5K), . It was $315 shipped for the 75 foot with their winter sale and the WINTER17 code. I'm planning on turning the factory line into an extension without ever using the winch with wire rope.

[TwinStick]

My trucks computer is always dead on..........unfortunately.

[OffroadTreks]

There is almost no relevant data in any of these threads. I data logged about 70k miles this year and can tell you exactly where my mileage is peak and where it started to suffer. I have a lot less miles in the PW but I can still tell you. On the highway, if I drive 55mph I get roughly 15mpg (15.5MPG on the computer). At 80mph I get about 11.5MPG. This is in optimal conditions. If I drive westbound on I84 in the gorge into the wind my mileage drops 2mpg to 3mpg. Up hill or down hill almost doesn't matter as long as I stay within those speed ranges. Stop and go traffic under 50MPH I get about 9MPG and less if I floor it from stops.

I've been using fuely for awhile. I see similar results with speeds as well. Our trip to Moab this past week, he had better mileage going because I averaged 62mph. This time I added an hour to the trip on the return by going a more scenic route and also pushed the truck more around 75mph. And saw a significant decline.

62mph seems to be a sweet spot for me. We don't do enough city driving for me to really track it, I generally track trips. We probably fill the truck once a month when not traveling or about every 3 1/2 weeks.

[nts007]

There is almost no relevant data in any of these threads. I data logged about 70k miles this year and can tell you exactly where my mileage is peak and where it started to suffer. I have a lot less miles in the PW but I can still tell you. On the highway, if I drive 55mph I get roughly 15mpg (15.5MPG on the computer). At 80mph I get about 11.5MPG. This is in optimal conditions. If I drive westbound on I84 in the gorge into the wind my mileage drops 2mpg to 3mpg. Up hill or down hill almost doesn't matter as long as I stay within those speed ranges. Stop and go traffic under 50MPH I get about 9MPG and less if I floor it from stops.

I've been using fuely for awhile. I see similar results with speeds as well. Our trip to Moab this past week, he had better mileage going because I averaged 62mph. This time I added an hour to the trip on the return by going a more scenic route and also pushed the truck more around 75mph. And saw a significant decline.

62mph seems to be a sweet spot for me. We don't do enough city driving for me to really track it, I generally track trips. We probably fill the truck once a month when not traveling or about every 3 1/2 weeks.

Fuel up every 3.5 weeks!!! I'm jealous. The truck I drive mostly gets a tank every 4-5 days haha. Maybe one day ll be able to retire and make a tank last a couple weeks lol

[OffroadTreks]

Wife and I work from home, and shop at Costco, which means, we almost never go anywhere other than on our little road trips.

Right now, I'm on a health kick, so most of my time is spent working out in favor of going out. So yeah, that's mainly why. I imagine if we had to commute regularly or something it would suck.

We do need to get around to buying a second vehicle, but I think we've been avoiding it because we want to move again, despite just having moved here last year.

[Bill2014]

I have compared the computer readout to hand calculations at every fill up with my new work truck (‘17 Ram 1500 with hemi). It was dead on once, the rest of the time the computer has read anywhere from .5-1 mpg more than the actual hand calculation shows.

As far as my Power Wagon, if I can muster 14mpg out of a tank I am doing good. Usually more around 12.5 or 13. That is normal country driving though, no highways/freeways etc. With the travel trailer hooked up I havnt seen much better than 9 mpg

I've noticed the same. I have not had the computer read the same as the hand calculations, and my results are the same as yours. What bothers me, and maybe I'm just weird, but the instantaneous MPG will never go negative even with my heavy foot.

Not sure where you were going with the concept of "negative" MPG... But that would require your truck generating fuel and putting it back in the tank. The lowest MPG a heavy foot can hope to achieve is still 0 MPG

[olyelr]

Not sure where you were going with the concept of "negative" MPG... But that would require your truck generating fuel and putting it back in the tank. The lowest MPG a heavy foot can hope to achieve is still 0 MPG

Well, lets just say the truck averaged a horrible 2 gallons per mile (no, not 2 miles per gallon, but 2 gallons per mile), which could be possible under heavy throttle conditions. What would the readout be for that?

[FordyceCreekTrail]

Can it really get that bad? I don't think under normal operating conditions it would. But say stuck in the mud flooring it...but then you are stuck and off road so who cares. My guess is if you let it idle forever or had a ridiculous off road session it could go down to 0 or 1MPG read out but would not go negative on the display. However, once you hit the road again that lost mileage would be included and it would take forever to get back up to normal.

[olyelr]

Can it really get that bad? I don't think under normal operating conditions it would. But say stuck in the mud flooring it...but then you are stuck and off road so who cares. My guess is if you let it idle forever or had a ridiculous off road session it could go down to 0 or 1MPG read out but would not go negative on the display. However, once you hit the road again that lost mileage would be included and it would take forever to get back up to normal.

Man I hope not

I think he was referring to instant MPG readout. Like when you are taking off towing an 8000 pound trailer, it does get down into the low single digits pretty easily (but never negative).

[Bill2014]

Not sure where you were going with the concept of "negative" MPG... But that would require your truck generating fuel and putting it back in the tank. The lowest MPG a heavy foot can hope to achieve is still 0 MPG

Well, lets just say the truck averaged a horrible 2 gallons per mile (no, not 2 miles per gallon, but 2 gallons per mile), which could be possible under heavy throttle conditions. What would the readout be for that?

Current MPG would likely read 0 and Average MPG would likely read 0.5 Your poor truck

[FordyceCreekTrail]

My Titan got into some real trouble one time. A road we always take that has never been any trouble turned into a nightmare, and I swung too far around someone I was trying to drag out and ended up in a pond. I bet I burned a qtr tank revving that V8 to redline over and over for an hours to get out.(trip canceled) Then another time I got stuck on that road towing and excavator! So mud bogging with an excavator that had to have been bad on fuel mileage. But if you get stuck, having an excavator in tow sure helps Did not even have to unload just push us along while someone drove the truck.

[Low_Sky]

My 2015's lie-o-meter is accurate for highway miles. Where it goes off is in city driving, and paints a rosier picture than reality. In city driving, the truck calculates about 0.5 to 1 mpg better than hand calculations. My guess is that the sample rate of whatever sensor is measuring fuel flow is too slow to catch the spikes that occur during acceleration in city driving. Highway driving is a nice steady condition, easy to measure accurately.