1651 mi rd trip, pulling 5th wheel about 10,000 lbs + gear, family etc

Day 1) Leave San Antonio > Angel Fire NM: Began at temp 34 F, drove at 66 mph, 349 mi day 1

Day 2) 751 mi temp in the 20's, 66-68 mph, total miles 759 upon arrival.

Mileage: Steady drop from 15.7 down to 8.6 mpg (note this is the LOWEST mpg I have ever got and I usually am hauling heavier around 12,000 lbs on business trips this was vacation, so no inventory.

Day 3 and 4 return) Temps 30's thru 50's, mpg steadily increases to 11.4 then dropped down to 11.0 on day 4 and stayed there, total miles 1651. Averag

Have almost 20,000 mi on truck about 9500 mi in actual towing miles.

I have never seen this variation. Almost always, it starts in the 14's or 15's from local driving, drops to around 10-11ish depending upon traffic and wind and stays there for the duration of the trip, then picks back up when I go local.

I drive at or cruise control a 62, 66, or 72 mph on all trips depending upon traffic and weather.

NEVER saw mpg in the 8's or ever drop down and then go back up?


Any thought on? Long regen maybe????

 

What was the wind like? I get 10-11 most of the time pulling but if the winds hit hard it drops.

 

The wind often is one of the biggest factors on mpg on these big square trucks

 

Should have mentioned, but since there was no wind either coming or going I forgot. Yes that wind can eat your lunch. Even driving into a head wind going to Houston I was still getting high 9's, about 9.8 or 9.6 the worst I have ever exp before this...

 

Wind and some grades are so subtle that you don't realize that your climbing.

 

And I'm guessing that you were climbing in elevation as you went West. It's gradual but it makes a big difference. And wind is almost always a westerly direction. Think of the way back; downhill and with the wind . .

Your variation is totally within the realm of what actually happens.

 

^^ This, probably ^^. You had quite the change in elevation from SA to Angel Fire. Probably 7000' or more.

 

Don, it may seem odd, but I can have variations of a couple MPG just based on what the ambient temp is for any given day. This is making the same exact round trip with the same wind and same traffic, on the same tank of fuel. It seems that temp starts to affect my mileage once it goes below about 60°, and gets slightly lower as the temps drop further. Likewise, they begin to rebound as temps come up. Regen is not an issue for me, so that isn't changing my mileage at all. Since it is the same tank of fuel, it is not summer blend versus winter blend.

 

Subtle grades really get me when I am towing.

 

Several possibilities:

1) It's a long uphill climb from San Antonio (650 ft elev) to Lubbock (~3300) to Angel Fire (8400)
2) (Unusually strong) Headwind?
3) Cold, dry air is more dense than warm, humid air... higher than normal aero drag?

HTH,
Jim / crewzer

 

I recentlyly completed a non towing trip 3,000 miles and noticed a 3% drop in mileage when forced to use B20 instead of B5 or less due to different regulations in different states. Winter blend in northern states could have also been a factor as well as travel was from the Canadian border to California and Arizona. B20 more expensive and lower mileage?

 

It could be a lot of things. Many already mentioned, plus my regens are longer and less predictable (start at 75% and continue for tens of miles after hitting 0%, for example) in the winter. I don't know if that's a fuel difference or an ambient temp difference.

 

I think we can all agree on elevation as it was uphill all the way and we made trips to Red River and Taos putting me up over 9000 ft.

When I used to got Moab to Jeep from Tx I would do a hard reboot on the ECM wen I arrived to force a faster adjustment to the elevation as those old Jeeps and that straight 6 were sensitive to changes.

Thanks to ALL for your contribution, you guys as aways got the answers...

 

I bet you also went from regular #2 diesel to Winterized fuel as you drove west.
Less BTU's in the winterized fuel, So figure that in with the elevation change