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Fuel Economy while towing

LeeroyJ

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Here is the story of me running out of gas on the first leg of a 3000 mile (4828km) roundtrip from Arizona to Oregon. I have B58 version of the Grenadier with 3/15/70 tires.

I had been driving for about 45 minutes. I was pulling my camper (~7000 pounds, 3175kgs). It was 112F (44.4C). I was on the I10 interstate in Arizona with cruise control set to 65mph (104.6kph). There was a 25mph (40kph) headwind. The grade was slight uphill. I was in the left lane passing an even slower vehicle when I reached an exit that had a sign that said something like, “Last services for 54 miles" (87kms). I could not get-over to exit in time. I could have done an illegal U-turn, but since the fuel gauge still showed 40% fuel remaining, I decided to keep going.

My average economy without towing has been 13.5 mpg (17.4 L/100km). Thinking about it, I thought that at 40% of the ~24gallon (~90.84L) tank I should have had approximately 9.6 gallons (36.34L) left giving me a range of ~129.6 miles (208.6 km) so it should have been no problem even accounting for less range with the trailer. But, the fuel level dropped alarmingly quickly and I started to worry I might not make the next fuel station. I passed a rest-stop and briefly debated pulling over and detaching the trailer to go get fuel, I should have done that.

The gauge finally hit the empty mark with 5 miles (8kms) left to the gas station. At 3.5 miles (5.6kms) to the fuel station (I could see the "Loves Truck Stop" sign and the big American flag) the engine started to sputter, I pulled off the interstate and the engine died. I disconnected the trailer and tried restarting it to see if maybe I could make it. No luck it wouldn't restart. I called USAA roadside assistance and they sent a guy with fuel (87 octane only), who put 3.5 gallons in. (I only had to pay for the fuel. We called other tow companies and they wanted between $250 and $650 to deliver the fuel, plus the cost of fuel, so I was glad we had the roadside assistance with USAA). We had to wait on the side of the interstate for about an hour and a half, but at least we had the air conditioning in the trailer. The Grenadier started immediately and we continued to the fuel station.

On the rest of the trip, I made all leg plans based on 150 mile (241kms) or less stops between fuel stops. That was not easy in some of the remote sections of Nevada, Arizona, California, and Oregon. It also meant I spent a lot of time at fuel stops, and often had to stop when I had only done about 55 miles in order to have enough range for the next longer stretch. I also was forced to get fuel at some stations that were very expensive - I paid from $4.20 per gallon ($1.11 per liter) to $6.40 per gallon ($1.69 per liter).

People talk about range anxiety with electric cars, but that's nothing compared to range anxiety towing with a petrol Grenadier. With my extended tank on my LC200 diesel, I could cover 1500kms (932 miles) (not towing), so this dramatic change in range was a surprise.

My actual fuel economy over this trip while towing worked out to 7.36mpg (31.95 L/100km).

Lessons learned:
1) When the fuel gauge hits empty, it has almost no reserve (1.5miles in my case).
(I'm used to having several gallons in reserve once you hit empty.)
2) Fuel economy drops drastically when towing
3) I need to get an extended tank and carry jerry cans
4) I need to do better route planning based on my actual mileage history.

Here is a screenshot of my fuel stops for that trip. (Note that the first line gallons includes 3.5 gallons from the jerry can.)
1721415165836.png


Some photos from the trip to make this thread more visually interesting:

Out of fuel on the side of I-10:
IMG_8793-X2.jpg

IMG_8792-X2.jpg


Had some great camping though - the high temp when we were on the Oregon coast was only 64F (17.8C).
IMG_8816-X2.jpg

IMG_8840-X2.jpg
 

DenisM

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@LeeroyJ : as a matter of interest what was your "usual" cruising speed on the trip while towing? I'm assuming it's well north of 50mph... Once you exceed about 50mph the inverse square law regarding aerodynamic drag applies well and truly...e.g. at 80mph it takes 2.56 times the energy to overcome the wind resistance compared to 50mph... So say (approximately ) twice the fuel consumption compared with cruising at 50 mph.... Like @bigleonski says, the Grenadier has the aerodynamics of a brick, so no consolation there! ;)
 

Tazzieman

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I don't believe petrol., brick and towing heavy are related to the word economy.
I always thought profligate consumption would be expected, but slightly better than an old Land Rover.
And it's true!
 

BenTN

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I've towed a 3500lb (loaded) camper ~6000mi per year for the past 4 years. Prior to the Grenadier it was towed by a 4-door Jeep Wrangler JLU with the standard 3.6L gas engine. Now I tow with the petrol Grenadier and it is a better experience all around. Both are live-axle 4WD with identical tires (BFG K02), gas engines, and the aerodynamics of a brick. Same exact camper and loading.

With the Jeep I was getting about 10mpg (vehicle-reported) towing all day at 70mph. A headwind or climb would raise consumption to ~9mpg and the Jeep was really not capable of pulling at 75mph. It would downshift and try to run at 4500rpm if I didn't force it to stay in a higher gear. The 20 gallon tank meant I had <180miles usable between gas stops. I towed all around the US west for 4 years without needing to use the spare fuel tank I carry.

The Grenadier gets ~10.5mpg to 11.5mpg (vehicle-reported) towing at 75mph. It does not slow down for interstate grades, and with the cruise control set it doesn't downshift past 6th so the rpm never climbs above 3200rpm. Haven't towed in a good sustained headwind yet. My range with the slightly larger Gren tank is >200mi. Plus it is a better towing experience in every way. I am happy.

Physics is a bitch.

Plan lots of gas stops. Stretch your legs and stay fresh.
 

AngusMacG

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Interesting take and good to know about towing. Jerry cans are a must. I have 10 gallons with me at all times even though I’m not towing because I dont trust the gas gauge (the remaining miles is utterly useless). I do rely on the miles driven as i can go about 315-320 miles before filling up and those fill up’s range between 21-23 gallons (varies depending on my average speed primarily)
 

LeeroyJ

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@LeeroyJ : as a matter of interest what was your "usual" cruising speed on the trip while towing? I'm assuming it's well north of 50mph... Once you exceed about 50mph the inverse square law regarding aerodynamic drag applies well and truly...e.g. at 80mph it takes 2.56 times the energy to overcome the wind resistance compared to 50mph... So say (approximately ) twice the fuel consumption compared with cruising at 50 mph.... Like @bigleonski says, the Grenadier has the aerodynamics of a brick, so no consolation there! ;)
It depended on where I was but usually between 55 and 65. Above that it feels too squirly with the trailer.
 

LeeroyJ

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......

The Grenadier gets ~10.5mpg to 11.5mpg (vehicle-reported) towing at 75mph. It does not slow down for interstate grades, and with the cruise control set it doesn't downshift past 6th so the rpm never climbs above 3200rpm. Haven't towed in a good sustained headwind yet. My range with the slightly larger Gren tank is >200mi. Plus it is a better towing experience in every way. I am happy.

......
You are getting a lot better mileage then. I don't exceed 65 when towing and get 7.4mpg. At 75 without towing I'm only getting about 12-13.
 

parb

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I usually drive between 65- 75mph. I usually get 17-18mpg
When in Nevada and Utah and the 80mph roads I drive 85-90mph, I usually get around 15-16mpg.
 

LeeroyJ

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I usually drive between 65- 75mph. I usually get 17-18mpg
When in Nevada and Utah and the 80mph roads I drive 85-90mph, I usually get around 15-16mpg.
I'm not sure why mine is so bad then... I don't drive fast.
 

parb

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I usually reduce speed a bit when going uphill, I find it makes a difference for my average fuel consumption. I do that with most cars though. And I rarely, if ever accelerate hard to get up to speed. I let it take a bit of time.

In my prior job I studied fuel consumption for different scenarios across my fleet of cars. We had amazing telemetry down to the second for anything and everything you can imagine that can be measured. The more smoothly the car was driven the better the fuel economy. I guess I adopted that philosophy in my personal driving style.

Fwiw in my prior job I developed vehicle software for autonomous (self driving) vehicles.
 

Tazzieman

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Every time you use the brakes it ruins your fuel economy.
Don't use your brakes unless you absolutely have to!
 

landmannnn

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I don't believe petrol., brick and towing heavy are related to the word economy.
I always thought profligate consumption would be expected, but slightly better than an old Land Rover.
And it's true!
I had one of those original V8 CSW 90 Land Rovers, average fuel economy was 12mpg (9 mpg US) without towing. Range on a full tank less than 150 miles.
So yes, the IG has better fuel consumption.
 

Tazzieman

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I had one of those original V8 CSW 90 Land Rovers, average fuel economy was 12mpg (9 mpg US) without towing. Range on a full tank less than 150 miles.
So yes, the IG has better fuel consumption.
Yes I had a 95 V8 Disco 1; terrible drinking habit.
But the 2 tonne LWB Landy with it's 1930s design 2.6L 6 is worse. Seriously , it needs to check into a facility for rehab.
 

emax

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Every time you use the brakes it ruins your fuel economy.
Don't use your brakes unless you absolutely have to!
This has been my preaching since 1871.

If you push the gas/diesel pedal, you burn more fuel, obviously. But you basically exchange fuel against kinetic energy. It is not lost like with braking.

And when you brake, you generally don't burn fuel in that moment - but you destroy all the kinetic energy you invested and exchange it for heat, which is distributed in space and is simply "gone", lost forever.

I fully agree: braking is the economy's biggest enemy.
 

Eric

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This has been my preaching since 1871.

If you push the gas/diesel pedal, you burn more fuel, obviously. But you basically exchange fuel against kinetic energy. It is not lost like with braking.

And when you brake, you generally don't burn fuel in that moment - but you destroy all the kinetic energy you invested and exchange it for heat, which is distributed in space and is simply "gone", lost forever.

I fully agree: braking is the economy's biggest enemy.
More interesting I'd like to see how the back brake pads last with heavy towing. My Discovery 4 would go through more/ the same back pads than the front pads with towing. Albeit they tended to be softer material than the front pads.
 

Mountain4x4

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The thing I learned about towing weight, and that Xplore is a beast. Is stop way more then you think, and if you are heavy you should have double or 75% more range then what your miles to empty shows to be safe. I can tow my camper with a lot less reserve then that with my Power Wagon, but go skid steer and dump trailer and it feels like you are stopping in every town.
 
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Here is the story of me running out of gas on the first leg of a 3000 mile (4828km) roundtrip from Arizona to Oregon. I have B58 version of the Grenadier with 3/15/70 tires.

I had been driving for about 45 minutes. I was pulling my camper (~7000 pounds, 3175kgs). It was 112F (44.4C). I was on the I10 interstate in Arizona with cruise control set to 65mph (104.6kph). There was a 25mph (40kph) headwind. The grade was slight uphill. I was in the left lane passing an even slower vehicle when I reached an exit that had a sign that said something like, “Last services for 54 miles" (87kms). I could not get-over to exit in time. I could have done an illegal U-turn, but since the fuel gauge still showed 40% fuel remaining, I decided to keep going.

My average economy without towing has been 13.5 mpg (17.4 L/100km). Thinking about it, I thought that at 40% of the ~24gallon (~90.84L) tank I should have had approximately 9.6 gallons (36.34L) left giving me a range of ~129.6 miles (208.6 km) so it should have been no problem even accounting for less range with the trailer. But, the fuel level dropped alarmingly quickly and I started to worry I might not make the next fuel station. I passed a rest-stop and briefly debated pulling over and detaching the trailer to go get fuel, I should have done that.

The gauge finally hit the empty mark with 5 miles (8kms) left to the gas station. At 3.5 miles (5.6kms) to the fuel station (I could see the "Loves Truck Stop" sign and the big American flag) the engine started to sputter, I pulled off the interstate and the engine died. I disconnected the trailer and tried restarting it to see if maybe I could make it. No luck it wouldn't restart. I called USAA roadside assistance and they sent a guy with fuel (87 octane only), who put 3.5 gallons in. (I only had to pay for the fuel. We called other tow companies and they wanted between $250 and $650 to deliver the fuel, plus the cost of fuel, so I was glad we had the roadside assistance with USAA). We had to wait on the side of the interstate for about an hour and a half, but at least we had the air conditioning in the trailer. The Grenadier started immediately and we continued to the fuel station.

On the rest of the trip, I made all leg plans based on 150 mile (241kms) or less stops between fuel stops. That was not easy in some of the remote sections of Nevada, Arizona, California, and Oregon. It also meant I spent a lot of time at fuel stops, and often had to stop when I had only done about 55 miles in order to have enough range for the next longer stretch. I also was forced to get fuel at some stations that were very expensive - I paid from $4.20 per gallon ($1.11 per liter) to $6.40 per gallon ($1.69 per liter).

People talk about range anxiety with electric cars, but that's nothing compared to range anxiety towing with a petrol Grenadier. With my extended tank on my LC200 diesel, I could cover 1500kms (932 miles) (not towing), so this dramatic change in range was a surprise.

My actual fuel economy over this trip while towing worked out to 7.36mpg (31.95 L/100km).

Lessons learned:
1) When the fuel gauge hits empty, it has almost no reserve (1.5miles in my case).
(I'm used to having several gallons in reserve once you hit empty.)
2) Fuel economy drops drastically when towing
3) I need to get an extended tank and carry jerry cans
4) I need to do better route planning based on my actual mileage history.

Here is a screenshot of my fuel stops for that trip. (Note that the first line gallons includes 3.5 gallons from the jerry can.)
View attachment 7864114

Some photos from the trip to make this thread more visually interesting:

Out of fuel on the side of I-10:
IMG_8793-X2.jpg

IMG_8792-X2.jpg


Had some great camping though - the high temp when we were on the Oregon coast was only 64F (17.8C).
IMG_8816-X2.jpg

IMG_8840-X2.jpg
Great color combo—13 mpg is pretty brutal.
 

Pistaah

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I recently towed a dumper back 180 miles from Leeds to Hereford, mostly motorway, mostly 50mph (endless average speed roadworks) bar the last hour and according to the Statistics screen averaged 23mpg, which I thought was pretty good - diesel engined Utility obvs. not petrol. Pretty happy with that and it towed well!
 

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