Towing van with 2016 D4 3.0 - which gear?

I only have a 2.7 D3, but I can tow comfortably at 100 in 6th. I do note a significant decrease in Oil/Coolant/Exhaust gas temps in 5th. Not noticed a real difference in fuel consumption, but the extra couple of hundred revs makes for a cooler motor.

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Originally Posted by Eric SDV6SE

Torque is dependant on speed and Power is a calculated value from both of these. Keeping speed as the constant (i.e. maintaining same road vehicle speed) both power and torque will vary. As said its a balancing act, higher rpm means less torque but more speed. Higher rpm also means more fuel and wear, but, higher engine rpm increases cooling efficiency of the engine (partly negated as these motors run a viscous coupled fan that locks at temperature presents not rpm).

Makes sense to me to run in a lower gear to increase engine rpm and therefore responsiveness, plus this makes less torque so the engine has less strain, but engine spins faster work harder to maintain speed and you may use more fuel.

Personally I just let the smarts of the car do this and when towing, it's normally in D. We saw flat 13.0l/100km when crossing the continent from West to East and back again. Never contemplated running in S on thr highway. Sometimes in manual when towing off road.

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Sorry not quite correct.

Look at your torque curve [emoji41]

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Originally Posted by Eric SDV6SE

Personally I just let the smarts of the car do this and when towing, it's normally in D. We saw flat 13.0l/100km when crossing the continent from West to East and back again. Never contemplated running in S on thr highway. Sometimes in manual when towing off road.

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Personally I do this too. My camper is about 1.8-1.9t loaded, with water. I never drive over 100kmh and I drive in D. Granted I don’t have an iid yet so I don’t know about exhaust temps but my TDV6 also hasn’t been remapped.

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Originally Posted by John_D4

Personally I do this too. My camper is about 1.8-1.9t loaded, with water. I never drive over 100kmh and I drive in D. Granted I don’t have an iid yet so I don’t know about exhaust temps but my TDV6 also hasn’t been remapped.

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Watch you instant fuel use on dash. Then try the next gear down if doing inclines.

:)

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Originally Posted by Tombie

Watch you instant fuel use on dash. Then try the next gear down if doing inclines.

:)

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Tombie my instant fuel readout shows a definite reduction in consumption - by up to 1.5 lph - when I drop to 7th, all other things being equal. So I figure from that, the engine is working less hard to maintain that constant speed, and therefore wear and tear is less. Am I right?

It means that the engine is more fuel efficient in the lower gear. If the same work is being done then the engine is working just as hard.

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Originally Posted by Graeme

It means that the engine is more fuel efficient in the lower gear. If the same work is being done then the engine is working just as hard.

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By definition that'd be correct. I look at it from another angle. More fuel efficient means less fuel for the same work, so less waste heat being generated (after all that extra fuel has to go somewhere). I also see lower boost pressures, so that'd result in lower combustion pressures which would be easier on both the rings and bearings. So while it's doing the same amount of "work", it's not working as "hard" to do it or to put it another way it's putting less stress on the engine to deliver the same amount of work.

Slightly off topic, i believe 5th gear in a 6 speed Puma is optimal. apart from revs, because it is a straight through shaft & is "stronger"
Do automatics have a "stronger" gear, or are all gears equal

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Originally Posted by AndyG

Slightly off topic, i believe 5th gear in a 6 speed Puma is optimal. apart from revs, because it is a straight through shaft & is "stronger"
Do automatics have a "stronger" gear, or are all gears equal

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Autos don’t seem to suffer this issue.

In our TDCI I still tow in 6th where it isn’t labouring the vehicle. Anything that loads it up (incline etc) and it’s back to 5th.

Sorry haven’t posted for a while and still travelling in FNQ.

I remember reading in the Owners manual that when towing (using tow assist) do not use Sport mode. some have mentioned that they do. Maybe somebody can confirm.

I’m also interested in why that is so.

David