4 cylinder turbo mileage towing

Dvanz · July 27, 2023

I have a travel trailer that weighs about 3700lbs. I’m getting about 8.5 mpg when towing in relatively flat highways in Michigan. Anyone doing better? I have transmission in drive with my tow/haul setting on & two wheel drive.

CamGTP · July 27, 2023

How fast are you going?

Dvanz · July 27, 2023

60 for about 150 miles, 70 for about 200 miles.

4banger · July 27, 2023

what's the trailer? big frontal area? also have you towed it with anything else? if so what was the other engine and what mileage did you get?

I tow 3000 dry trailer a lot, but small frontal area v-nose as it's a 6' wide x 6' interior height cargo trailer done as a van life off grid 4-season build. my truck is 4x4 with 4" lift and 985 lbs of fuel and gear added to it, and depending on missions we are adding a few hundred lbs to maybe 1000 lbs of gear etc. between the truck and trailer. Just went from edge of prairies across the mountains to northern tip of Sonora desert and back 445 miles one way and back at a good clip, I pass like I'm empty on the passing lanes etc. and will run it up to 80 mph plus to get around the semi trucks on the climbs etc. but typical speeds are 68 mph and we averaged about 19.8 l/100 km going there and 22.0 coming home which is 11.9 mpg and 10.7 mph. We did some 200 mile trips to chase sturgeon on the prairies and fast two lane speed limits where I averaged around 75 mpg and got 24 l/100km (similar to when I had a 6.2 rental and flogged it home for 800 kms at those speeds btw) which is 9.8 mpg....so there's something seriously wrong with your number imo. I'm in a 2022 refresh and you can see my rig below. We can boogie at left lane traffic speeds anytime we like and that motor can pull the power required to do so...like either of the v8 options, and correspondingly it will pull the fuel but 8.5 mpg...no, that's 27.7 l/100km, that would be wide open throttle climbing hills or doing 90 mph down the road imo. my rig should be pictured in my signature for reference...my towing mileage if I really behave is stated in my signature, as high as 12.7 mpg, at 60 mph and 70 mph you should 11-13 mpg in my guess, I use tow/haul mode most of the time also, sometimes I forget, truck doesn't care with my trailer...you sure you're 3700? is that dry, is it a full 8' wide big ole travel trailer? it should still pull double digit mileage even if you were 5500 lbs wet

Edited July 27, 2023 by 4banger

4banger · July 28, 2023

also I'm running 33x10" load range e tires about 36 psi front and 40 psi rear...not sure it's a factor but some guys put serious fatties on their rigs that could cut mileage down some too?

David Van Houzen · July 28, 2023

11 hours ago, 4banger said:

also I'm running 33x10" load range e tires about 36 psi front and 40 psi rear...not sure it's a factor but some guys put serious fatties on their rigs that could cut mileage down some too?

I’m sure my loaded weight is higher. The 3700 lbs is dry weight of trailer but I would say loaded it’s about 4500 lbs. The travel trailer has a front end that’s about 10’ high x 8’ wide. It is curved at the top for aerodynamics. Ps, thanks for your response.

David Van Houzen · July 28, 2023

My friend, who is a retired GM engine guru, says my tow mode is probably blocking my turbo from locking? He suggested to try staying out of tow mode and see if that improves my mpg.

David Van Houzen · July 28, 2023

the wanderer · July 28, 2023

Turbos suck back fuel when working hard. That is the price you pay for owning them vs a N/A. They're slightly better MPG when driven calmly, but slightly worse when driven hard.

I would NOT disable tow mode to try and save a few bucks. Tow mode is designed to be used towing that kind of trailer, whatever the transmission does in tow mode is going to save the life of it.

Maybe your 8 speed is different, but my 8 speed (from ZF/ram) definitely locks the torque converter in T/H mode. TH basically changes the shift points to keep the RPMs up for more power, and downshifts sooner when braking to give more engine braking.

If you're new to towing, these tips may help:

Try to stay below 65 mph, and stay off the pedals. Every time you brake, you're wasting energy as you will need to dump more fuel to get back up to speed again. So keep a large distance in front of you and just try to slowly accelerate and slowly decelerate. Drive like you have an egg between your foot and the pedal. Don't use cruise control as it will try to hold your speed constant instead of allowing you to coast and cruise up and down hills varying your speed.

newdude · July 28, 2023

2 hours ago, David Van Houzen said:

My friend, who is a retired GM engine guru, says my tow mode is probably blocking my turbo from locking? He suggested to try staying out of tow mode and see if that improves my mpg.

Turbos don't lock.

Are you thinking torque converter? Because the torque converter locks with or without tow/haul on.

Try driving with it off, and put the transmission into "L7" so shift all the way down, press the "+" on the rocker on the shifter until you see "L7". This will lock out 8th gear which will put you at about 2000rpm at 60mph so out of the low RPM lug and more into the meat of the torque. Also, speed. 70mph with a brick behind you creates a LOT more wind resistance than that same brick at 65mph and 60mph and so on.

Tow/Haul Mode Description and Operation

Tow/haul mode is a function within the vehicle's software/calibration that optimizes transmission gear selection for operation during towing or with heavy loads. This optimization includes improving acceleration performance during launches, reducing shift busyness, assisting brake performance and speed control during engine braking situations, and improving vehicle speed control while requiring less throttle pedal activity.

In general, tow/haul mode maintains lower gears longer and increases shift pressures. It is designed to be most effective when the vehicle and trailer combined weight is at least 75% of the vehicle's Gross Combined Weight Rating (GCWR). Operation of tow/haul in a lightly loaded or non-loaded vehicle will not cause damage. However, there is no benefit to the selection of tow/haul when the vehicle is unloaded, and use of tow/haul mode during unloaded driving conditions will decrease fuel economy and may generate shift feel concerns.

4banger · July 28, 2023

there was one stint as I recollect where I saw that sort of mileage with my rig, we left town into a very strong headwind coming out of the mountains while we climbed into the mountains that first 60 miles or so on 4 lane traffic was ripping so we stayed with it around 75-80 mph....then I saw about 27 l/100 km but by the time we reached our destination 3x further away it calmed back down to normal...still sounds like something is up, you do have a lot of frontal area, what are the rpms like while you're towing? is the thing constantly in the 4000 rpm range and sounding like its working hard?

could be something else like the trailer brakes dragging? just thinking out loud, your trailer doesn't look that bad, you should get down the road at 65 in double digits like 11 mpg imo

Edited July 28, 2023 by 4banger

David Van Houzen · July 28, 2023

That’s right, it was torque converter (we were having a beer on their boat) I forgot! Anyway thanks to both of you, I’m heading out next week and I’ll try some of your suggestions.