Real world truthful gas mileage

[johnfr80504]

I have kept detailed records of our MPG since purchasing our Monaco Cayman in 2019. I had 4025 miles on it when we bought it.

For the first 5025 miles we were towing a 2007 Jeep Liberty that weighed about 4300 lbs. Overall mileage was 8.21 mpg.

Winter of 2019 we traded the liberty for a Wrangler Rubicon that weighs about 4800 lbs. We saw a significant drop in mileage. For the next 9500 miles our overall was 7.61 mpg.

In Sept. 21, I installed a Diesel Pro Model 12000 performance module. This unit was advertised to improve performance and mpg. We made a 4500 mile trip to the east coast this fall with the module in place. We saw an immediate increase in mpg from 7.72 to 8.4 mpg. On the last leg of the trip I noted a noticeable drop in mpg and power during the final 500 miles.

A trip to the repair shop for oil change and investigation on low power revealed that the electric lift pump was on its last legs and actually failed during trouble shooting. I believe the reduced fuel pressure at the injector pump was the cause of the drop in mpg I noted. The shop believed the fuel pump failed due to the fact the rig sat for 11 years with no use.

Below are copies of my records.

[saddlesore]

ISM-11 @500hp..42k lb coach + tow.. 120k miles 7.1 MPG. most times also have the 10k generator going too.

[Rob_M]

I’ve compared actual fill up to fill up compared to what my scangaugeD says and it’s very accurate.

Everybody drives different so I’m not sure how a forum comparing “real world” fuel mileage helps anybody.

This past Saturday I averaged right at 11 miles per gallon Austin to Tulsa and then got up Saturday and went from Tulsa to St. Louis fighting a head wind and only averaged 8 miles per gallon going 5mph slower.

[High Road Travelers]

With our V10, 6 speed transmission, 34 foot MH, always towing a jeep; we average about 6.5 mpg. That's going through all types of terrain and we drive fairly conservative on state highways and about 65 - 67 mph on interstates.

[paddykern]

22' B+ (C) Sprinter
Average 16.5 MPG
Measured miles/pump gallons.

[Grabcon]

I use a phone app called SimplyAuto and track all of my vehicles. Here are the stats for two RV's

2003 Thor Fun mover, E450 Triton V10, 31 foot toy hauler with two motorcycles inside and a Jeep Liberty toad. 9403 miles, 6.88 mpg. GVWR 14300

2007 Damon Outlaw 3611 Toy Hauler, workhorse chassis, 8.1 Vortex, 37 feet, two motorcycles inside and a Jeep Liberty toad. 2879 miles, 6.83 mpg. GVWR 24000

[bentjm]

2005 MADP 4032. 32,300 lbs when not towing. 37,600 when towing.

I average 6.7 mpg when towing with the generator running. Run around the speed limit.

Not towing and not running the generator, I get 7.5 mpg.

So, real world, I can comfortably go 800 miles with my 150 gallon tank before I feel the need to fill up.

[Country Road]

What I’ve found is that the newer the vehicle, the more accurate the computer mpg is. Years ago, my 2000 Ford dually would always give me readings several mpg off from actual hand figured mpg.
New vehicles are very accurate but readings need to be computed over the entire trip.

[yeloduster]

Yep, I do keep records on actual mileage. Attached is a spreadsheet with my numbers. Note, I keep track of the generator hours and calculate the amount of fuel the generator uses and back that out of the total fuel. I think my algorithm for generator fuel usage is about right because the reported MPG seems to be unaffected regardless of generator usage.

Some state that their fuel economy is less when driving in the mountains. Mine is not really affected by terrain. What goes up must come down. I get really poor mileage going up and really good mileage going down and it averages out! I live in Colorado so all my trips have a bunch of up and down.

I think my really good mileage is when I had a stiff tailwind and really bad mileage is when I had a stiff headwind.

If you look through the spreadsheet you will see that my best MPG was 10.7 and the worst was 5.3! As you can see the overall average is 7.1 MPG

2003 34' Georgetown on a W20 Workhorse chassis. 8.1L V8 and Allison 5 speed. I added a UltrRv tune somewhere in there. I don't think it made a difference in fuel economy.

[dizcom]

Wow! Some people really go to town to get exact figures! We don't track our mileage. I wouldn't know what to do with the information if I did. So my coach gets exactly 7.216 MPG on average. That means that I sometimes get more and sometimes I get less. It doesn't tell me what my range is because it doesn't factor, hills, traffic, weather, extra stops for the dog, extra stops for the driver, rolling resistance over different blends of asphalt, wind, use of the AC, or anything else that would change the mileage up or down for that day's driving.



Is there anyone out there that actually uses these precise numbers to figure out where to refuel? Or would a big round number work just as well? Anyone use anything after the decimal, or do you just figure range using the rounded whole number and then leave yourself some cushion? All very scientific, of course. Anyone using those extra digits to determine the length of your next leg? How often are you wrong? Does anyone use them at all? For what??? I don't get a lot of things that people spend time on, but this one has me boggled. Bragging rights? Just guessing now. Someone enlighten me.

[Killtimer]

Here's a shout out from one of the little guys. LTV W24RTB AWD on a 2020 Ford Transit 3500HD chassis, V6 ecoboost, 10 speed. 16.5 liters per 100 km, 17.12 mpg (Imperial), 14.25 mpg (US). Lots of wind, some mountains and about 50% of 2000# trailer towing. Usually running the rig in "Eco mode" ECU setting.


On the subject of manual/factory fuel economy reporting, both of my ecoboost Fords dashboard readouts were about 5% optimistic until I adjusted the bias through the accessible engineering screen. They're both now within 1% constantly. I'm using an app called Road Trip on my phone to track all trip expenses including fuel. Great app.

[Killtimer]

Originally Posted by dizcom

I don't get a lot of things that people spend time on, but this one has me boggled. Bragging rights? Just guessing now. Someone enlighten me.

Nailed it!!!

[momdoc]

We have logged over 24K miles in our DP rig (2018 Tiffin RED 37PA) and depending on type of highway and terrain over the last 3 years we have averaged 8.3-8.8 MPG.

[yeloduster]

Originally Posted by dizcom

Wow! Some people really go to town to get exact figures! We don't track our mileage. I wouldn't know what to do with the information if I did. So my coach gets exactly 7.216 MPG on average. That means that I sometimes get more and sometimes I get less. It doesn't tell me what my range is because it doesn't factor, hills, traffic, weather, extra stops for the dog, extra stops for the driver, rolling resistance over different blends of asphalt, wind, use of the AC, or anything else that would change the mileage up or down for that day's driving.



Is there anyone out there that actually uses these precise numbers to figure out where to refuel? Or would a big round number work just as well? Anyone use anything after the decimal, or do you just figure range using the rounded whole number and then leave yourself some cushion? All very scientific, of course. Anyone using those extra digits to determine the length of your next leg? How often are you wrong? Does anyone use them at all? For what??? I don't get a lot of things that people spend time on, but this one has me boggled. Bragging rights? Just guessing now. Someone enlighten me.

I can't speak for anyone else but I do it because I can and I am a little OCD!

What do I do with the numbers? Changes in MPG can be a precursor to a problem. Maybe get it fixed before it breaks! But really...it just because I am a little OCD!

Oh yeah. I also do it so I can answer the OP's question!