Long trip fuel mileage

[DHayden]

Took a trip to Thousand Oaks CA from Las Cruces NM. First nice long trip I was able to do a lot of calculating. The lie-ometer was actually pretty accurate (overall). Leaving NM I started at about 13.2mpg and went up to 13.7 as I got close to AZ border.
Once in AZ mileage steadily increased to 15.9, strange because terrain is pretty much the same (flat) and winds were mild if any. On the west side of AZ into CA mileage increased to 16.3 and even hit 17.2! I had never seen the lie-ometer ever go above 15mpg with my regular driving around NM. Traffic turned to crap in CA of course and for the last 150 miles of the trip highway traffic was stop and go, crawling along mostly under 10-15 miles an hour if not stopped period.
I might expect a big swing in mileage if the fuel was different from state to state however, I have the 75 gallon transfer flow tank and all fuel was purchased at the same station in NM. I also installed the 40 gallon aux tank out of the 2001 which I just topped off the 75 gallon tank for the way back.
trip there 865 miles, Lie-ometer says 15.5mpg avg, calculated by gallons used 15.3mpg
trip back 859 miles, Lie-ometer says 15.2mpg avg, calculated by gallons used 15mpg
There was more stop and go traffic on the way back. The mileage decreased in reverse of its increases on the trip there. The whole trip is (mostly flat) so elevation is the main factor I can think of. I have calculated a lot of miles over the years and I'm having trouble trying to put this mileage swing into perspective. I know it could be off because I am using the trax 4 system to tell me how many gallons I used total but it seems pretty darn close to me between the trip there and the trip back.
Thought it was pretty good mileage for a 4x4 dually with 19.5s and loaded up with fuel and coolers. I NEVER would have though it would have crossed 16mpg much less 17mpg.

 

[Azbeachbum]

2022 3500 SRW 3.73 6.7HO 18.86 by hand calc. 400 mile RT in AZ running 75 empty

 

[CoastyAV8R]

Took a trip to Thousand Oaks CA from Las Cruces NM. First nice long trip I was able to do a lot of calculating. The lie-ometer was actually pretty accurate (overall). Leaving NM I started at about 13.2mpg and went up to 13.7 as I got close to AZ border.
Once in AZ mileage steadily increased to 15.9, strange because terrain is pretty much the same (flat) and winds were mild if any. On the west side of AZ into CA mileage increased to 16.3 and even hit 17.2! I had never seen the lie-ometer ever go above 15mpg with my regular driving around NM. Traffic turned to crap in CA of course and for the last 150 miles of the trip highway traffic was stop and go, crawling along mostly under 10-15 miles an hour if not stopped period.
I might expect a big swing in mileage if the fuel was different from state to state however, I have the 75 gallon transfer flow tank and all fuel was purchased at the same station in NM. I also installed the 40 gallon aux tank out of the 2001 which I just topped off the 75 gallon tank for the way back.
trip there 865 miles, Lie-ometer says 15.5mpg avg, calculated by gallons used 15.3mpg
trip back 859 miles, Lie-ometer says 15.2mpg avg, calculated by gallons used 15mpg
There was more stop and go traffic on the way back. The mileage decreased in reverse of its increases on the trip there. The whole trip is (mostly flat) so elevation is the main factor I can think of. I have calculated a lot of miles over the years and I'm having trouble trying to put this mileage swing into perspective. I know it could be off because I am using the trax 4 system to tell me how many gallons I used total but it seems pretty darn close to me between the trip there and the trip back.
Thought it was pretty good mileage for a 4x4 dually with 19.5s and loaded up with fuel and coolers. I NEVER would have though it would have crossed 16mpg much less 17mpg.

What speed were you driving and were you empty or loaded?

 

[bcbender]

I found on my 04, (305/555 with 4:10s),. If I stayed around 60 she could kick down 20s door... but who does that.

My new 6.7 is reliably returning 16 combined... I've seen as high as 18~19 but not unless Im driving miss daisy, and I never spend enought time on the highway empty steady state to see what the true top is... But all in all, she is just about as thirsty as my 04 was; and I am happy with that.

 

[DHayden]

What speed were you driving and were you empty or loaded?

On the highway was between 70 and 75. The stop and go really killed it. I Had about 1600 pounds between fuel, tanks, people, dogs and luggage.

 

[slowmover]

1). Need Engine Hours run against Odometer to see Average MPH.
2). MPG is an analysis tool: How closely one keeps travel speed against the actual average is indicative of skill.

— From here your reported MPG highs indicate stretches with low traffic volume without undue stops: no lane changes, no accel/decel events, time at steady-state highest.

But that road is never empty.

A five-mph speed variance means cruise control not in use? (Or one is one of the clueless running the posted maximum; mixing with car drivers all day).

There’s fuel being burned unnecessarily to achieve nearly the same actual average MPH is a good working assumption.

1). Example is: one is never in a left lane crowd to get around a vehicle in the travel lane. Vehicle control requires maximum spacing from others.
Plan ahead.

Get the whole set of numbers and the analysis of how conditions modify them gets interesting, fast.

THEN the MPG read-out becomes a tool. Mines off 11% at 60-mph (reads high). Knowing that factor I can “see” ACCURATE returns against conditions of road, load & weather. (Exact burn). Doesn’t take a long trip to know how the truck will do, generally.

.

 

[bcbender]

Mines off 11% at 60-mph (reads high).

Both my Ram trucks were about that...I could pretty much count on the EVIC / Overhead being about 10% when hand calculating.

 

[DHayden]

The 70/75 variation was due to the speed limit. I wasnt in a hurry and hadnt even planned on doing 75 when that was the limit but the truck didnt seem to mind. My 2001 really liked being in the 1750-1850rpm range for mileage. I was surprised to see that the 2015 liked being around 2100rpm (I have 4.10 rear). I do have the hour log of the trip also but I should have compiled everything the first 100 miles into CA before the stop and go started. I could have gotten some really good data. Its funny how when your faced with stupid traffic and long waits how you just want to get through it instead of waiting even 15 minutes (to write down calculations) because the traffic will be even worse.

 

[AH64ID]

I had two tanks this month that the EVIC registered low on, one by 1.8% (600 mile tank, 51.4 average but hauling the mail for 400 of those miles and short run city driving for 100 of them) and the other by 3.6% (389 mile tank, 49 mph average with mostly highway driving but some city mixed in).

I generally average an 8% error, but have seen swings from 20% optimistic to 9% under. It seems to have the most error on partial towing tanks. Tanks where I tow for 100% of the miles are fairly accurate at around 3% error and range from 5.9% optimistic to .2% under.

So it seems that the 2018's EVIC has the biggest issue with mixed use.

My 05 was ~17.5% off most years on the stock motor and I got that to drop closer to 10% with the BBi Stage 1's and a new duration table, thou it still swung quite a bit.

 

[slowmover]

So, it’s not a “lie-o-meter”, but a useful tool while underway was the point about understanding some built-in error versus fuel range.

Calculating a new fuel stop versus the one planned last night (trip plan done before leaving; otherwise you just ain’t at all serious about fuel burn) due to maybe a truly terrible wreck jamming highway several hours, an ill passenger, etc, is not falling below 80% empty worst case.

The MPG meter gives me some feedback on how things are going right there, right now. Fill before crossing major metro, or after? That half-hour off-road may matter as traffic worsens. Or, it’s better to stop now and get all things and persons into good order.

 

[slowmover]

I had two tanks this month that the EVIC registered low on, one by 1.8% (600 mile tank, 51.4 average but hauling the mail for 400 of those miles and short run city driving for 100 of them) and the other by 3.6% (389 mile tank, 49 mph average with mostly highway driving but some city mixed in).

I generally average an 8% error, but have seen swings from 20% optimistic to 9% under. It seems to have the most error on partial towing tanks. Tanks where I tow for 100% of the miles are fairly accurate at around 3% error and range from 5.9% optimistic to .2% under.

So it seems that the 2018's EVIC has the biggest issue with mixed use.

My 05 was ~17.5% off most years on the stock motor and I got that to drop closer to 10% with the BBi Stage 1's and a new duration table, thou it still swung quite a bit.

On current PACCAR and Cummins (Auto-shift) they’re very slow to acquire tenths of a MPG, but don’t shed them rapidly either (hundreds of miles into a day). Unless the Interstate is more-or-less a metro highway for great, long distances. (Computer checks it’s Sat-Tel database for shift data and decides you ain’t gonna do so well with what’s ahead). Can’t prove it, but you can’t rock it out of feeling depressed (so to speak).

 

[slowmover]

The 70/75 variation was due to the speed limit. I wasnt in a hurry and hadnt even planned on doing 75 when that was the limit but the truck didnt seem to mind. My 2001 really liked being in the 1750-1850rpm range for mileage. I was surprised to see that the 2015 liked being around 2100rpm (I have 4.10 rear). I do have the hour log of the trip also but I should have compiled everything the first 100 miles into CA before the stop and go started. I could have gotten some really good data. Its funny how when your faced with stupid traffic and long waits how you just want to get through it instead of waiting even 15 minutes (to write down calculations) because the traffic will be even worse.

60-mph is a literal wall so far as MPG is concerned. My ‘04 runs 59 at 1,725-rpm +/- That’s where I’m guaranteed 24-MPG for planning purposes despite load, road, traffic, weather, day/night across South-Central US. (Actual is 25).

With a 700-mile range at 80% fuel stops are easy to plan. From the world of truck-driving, they’re huge time-sinks. I’m not ever going to be so stupid as to run that far in a day (everyone’s reactions have gone to hell at mile mark 400 and one has slammed a wall at 600), so it’s E-Z to plan a stop at any point in the day for fuel.

One combines it with the hour lunch break if desired (otherwise stops are 15-20” every two hours). Get fuel and hit nearest rest area (stay out of fast food & C-stores).

Known stops = executing each leg with attentiveness. Clock is a friend, not a master.

The key is maximization of steady-state. Which is while on cruise control. Engage it coming down entrance ramp. Dis-engage when exiting. Find the speed which keeps one OUT of packs forming and dissipating. The stupids will pass you 2-3X in a day. But don’t get there sooner (and why would that that matter?).

Engine hours ON cruise for the day it is surprisingly difficult to meet 50%. I’ve been using CC fifty years and not until I ran for a company where we could chart it did I realize how hard it was to get CC use to 50% (not all OTR truck/driving days are long-distance).

In the CTD, my higher-than-some-of-you-believe numbers are achieved by knowing how to glide around non-highway to/from stops: I’ve used satellite data to choose stops and how to maneuver vehicle in advance. Since I’ve done it for so long, there’s no extra effort in this.

— What’s the best fuel stop among several at a location? The one in the same direction of travel and next to the highway entrance ramp. “Saving” pennies not valid alternative (should have done that the rest of the year). Felt momentum also important. In-Out-Gone

Zero idle time.

You do it right and the truth-o-meter will only lose a few tenths for a break planned in advance. Or you’ll pay for your sloppiness. (7/10s is my good/bad mark).

From disengaging CC slowing for exit ramp (Mark) to re-engaging set speed after leaving stop (Mark). This is the time and the penalty. (Set stopwatch and just learn to observe HOW you’ve been managing stops).

Get out of the trucks way. You steer & brake, let the computer run the drivetrain. Pays

.

 

[JLEONARD]

I got 22+ on a trip from FL to CT and back last summer. 70/75 on the interstate, A/C on, bed maybe 1/3 loaded. Daily I'm around 17 depending.

 

[Alan Reagan]

Last weekend, I got 25 mpg on a 200 mile trip down to coastal Georgia. That was running the speed limit (55 on 2 lane and 65 on the 4 lane). Coming back, same route I cut my speed to 62 on the 4 lane and kept 55 on the 2 lane and got 26 mpg. Of course I wasn’t towing anything. I usually take my tools on a flatbed but this trip, I just loaded them in the bed. Now, if I’m bucking a headwind I drop at least 2 mpg. I make this trip every other week and fuel where I live was $4.50/gal. On the coast it was $5.09. So I run the speed limit or less and save some money on fuel.