Fuel Mileage - While Towing

GMCanuck · April 9, 2011

So I realize that a "Fuel Mileage" discussion on a truck forum is often seen as senseless, but I need to ask...

Our 2006 Sierra, 5.3L gets around 20 mpg on the highway. Today, we picked up our new travel trailer and the mileage at one point dropped to around 8 mpg . So I need to know if this is normal or what the heck is going on...

The trailer is a 24ft, with a dry weight of about 5500 lbs. Speed was around 60 to 65 mph. Slight cross wind and rain, but nothing crazy. Stayed out of OD, RPM around 2500 to 3000.

So should I be concerned here or what exactly is going on???

pink1632 · April 9, 2011

So I realize that a "Fuel Mileage" discussion on a truck forum is often seen as senseless, but I need to ask...

Our 2006 Sierra, 5.3L gets around 20 mpg on the highway. Today, we picked up our new travel trailer and the mileage at one point dropped to around 8 mpg . So I need to know if this is normal or what the heck is going on...

The trailer is a 24ft, with a dry weight of about 5500 lbs. Speed was around 60 to 65 mph. Slight cross wind and rain, but nothing crazy. Stayed out of OD, RPM around 2500 to 3000.

So should I be concerned here or what exactly is going on???

I would say it's fairly normal, my '02 gets 16mpg all around driving but pulling my trailer which weighs right at the same as yours gets on average of 11mpg. I pull my trailer at 60, very seldom over that, no OD and in tow/haul all the time except while in town then it's 3rd gear. I try to be as easy on my engine as I can so keep a close watch on the RPM and downshift when necessary.... I wouldn't worry too much about the 8mpg, it could be better but not much.

music · April 9, 2011

That's a little low, but not much. Speed will affect mpg towing more than anything. If you stay in the range of 60 to 65 on the highway, it helps. More importantly, ST trailer tires are only rated to 65 mph, and can get pretty hot running fast. There is no good reason to drive quicker, but *many* reasons to go slower. When we tow, I plan for a slow drive... which may take an extra day or two of traveling on longer trips, but it's more relaxing. Also, verify tire pressures on truck and trailer, and make sure the camper is sitting pretty level, or very slightly nose down.

I've pulled ours (~6900 lbs loaded / ~5600 lbs empty) on a few 500+ mile trips, and the average has been 10 to 11 running 60 to 65 (maybe higher sometimes by accident). Pulling local, even into the Smokies, I usually average 10+. I use 3rd gear, unless it's pretty flat. Economy may be hurt by ~1 mpg (if that), but the 4L60 is much happier and runs cooler.

Edit: Should also point out that these results are similar for most gas motors when towing. Running higher rpms is generally more efficient when towing, *if* the motor isn't making too much excess power at that rpm/speed.

terzmo · April 9, 2011

So I realize that a "Fuel Mileage" discussion on a truck forum is often seen as senseless, but I need to ask...

Our 2006 Sierra, 5.3L gets around 20 mpg on the highway. Today, we picked up our new travel trailer and the mileage at one point dropped to around 8 mpg . So I need to know if this is normal or what the heck is going on...

The trailer is a 24ft, with a dry weight of about 5500 lbs. Speed was around 60 to 65 mph. Slight cross wind and rain, but nothing crazy. Stayed out of OD, RPM around 2500 to 3000.

So should I be concerned here or what exactly is going on???

That seems extreme to Me...are You "horsing it" when towing ? I get 18 in the city and over 13 towing a loaded one car trailer...with A/C...5.3/6 speed...have yet to go on a long trip without a trailer swo don't know highway mileage

music · April 9, 2011

That seems extreme to Me...are You "horsing it" when towing ? I get 18 in the city and over 13 towing a loaded one car trailer...with A/C...5.3/6 speed...have yet to go on a long trip without a trailer swo don't know highway mileage

Remember, a camper is a wind sail... and a big one at that. The added air resistance eats up 2 to 3 mpg, more so than added weight. In fact, our previous camper was less than 5k lbs loaded, and maybe 22 ft bumper/tongue. I averaged ~1 mpg better with it... so not much.

nbscanuck · April 9, 2011

Sounds about right to me. I tow in fairly flat country, but quite windy. Into the wind 6-8mpg, with the wind 10-12.

wurgs · April 9, 2011

Sounds about right, maybe a hair low but wouldn't worry about it. I get 8-12 mpg towing a 7500lb 26 footer. Like mentioned above its like having a sail attached to the back. Its not the weight but the shape of what you're towing. I can get 14-15 towing a 18' boat

GPSilverado · April 10, 2011

I would think your mileage is pretty close. I tow a 23 foot Grady White boat, which weighs in around 6500 - 7000 lbs when loaded and ready for fishing including trailer weight. My truck came with 3.42 gears, and I towed in 3rd. It took me a full tank (20 - 21 gallons useable) to go to a lake 2 hrs away and back. Actual mileage has always been calculated at 9-10 mpg driving 55 -65. Going to another lake, just a bit less distance, but with Interstate most of the way, I was geting the same results on the tank of fuel, but mileage was down to 8 -9 mpg while running anywhere from 60 -70 mph, but also encountering inclines that were more pronounced, with less flat stretches of road. My rpm's were usually 2400 - 2700 with the 3.42 gears.

Changing to 4.10 gears actually helped the fuel mileage, and now I use about 1.5 - 2 gallons less on the trip not traveling the interstate, still in 3rd, but at 2500 - 2800 rpm's. The Interstate trips are almost the same, but if I use 3rd, I am at 2700 - 3100 rpm's, so I find myself using Drive more often, which actually uses more fuel, but turns less rpm's. Drive puts the engine below the torque range, and works the engine much harder even though it is turning less rpm's.

I have found that if I can drive around 60mph, in 3rd, I get the best mileage when towing due to less drag from the wind, but increasing the rpm's into the 2600 - 2700 range for more efficient power.

In your situation, you have a much larger wind drag, so lower speed may help, but IMO, I would always want the engine turning somewhere around 2500 rpm for best results.

On a side note, I think the 3.73 would be the best gear for the 4spd trucks with stock tire sizes, since 3rd is still turning an acceptable amount of rpms at highway speeds. I LOVE the 4.10 gears, but I feel the need to drive about 5 mph slower when towing in 3rd on the interstates.

Ironmask555 · April 10, 2011

I would think your mileage is pretty close. I tow a 23 foot Grady White boat, which weighs in around 6500 - 7000 lbs when loaded and ready for fishing including trailer weight. My truck came with 3.42 gears, and I towed in 3rd. It took me a full tank (20 - 21 gallons useable) to go to a lake 2 hrs away and back. Actual mileage has always been calculated at 9-10 mpg driving 55 -65. Going to another lake, just a bit less distance, but with Interstate most of the way, I was geting the same results on the tank of fuel, but mileage was down to 8 -9 mpg while running anywhere from 60 -70 mph, but also encountering inclines that were more pronounced, with less flat stretches of road. My rpm's were usually 2400 - 2700 with the 3.42 gears.

Changing to 4.10 gears actually helped the fuel mileage, and now I use about 1.5 - 2 gallons less on the trip not traveling the interstate, still in 3rd, but at 2500 - 2800 rpm's. The Interstate trips are almost the same, but if I use 3rd, I am at 2700 - 3100 rpm's, so I find myself using Drive more often, which actually uses more fuel, but turns less rpm's. Drive puts the engine below the torque range, and works the engine much harder even though it is turning less rpm's.

I have found that if I can drive around 60mph, in 3rd, I get the best mileage when towing due to less drag from the wind, but increasing the rpm's into the 2600 - 2700 range for more efficient power.

In your situation, you have a much larger wind drag, so lower speed may help, but IMO, I would always want the engine turning somewhere around 2500 rpm for best results.

On a side note, I think the 3.73 would be the best gear for the 4spd trucks with stock tire sizes, since 3rd is still turning an acceptable amount of rpms at highway speeds. I LOVE the 4.10 gears, but I feel the need to drive about 5 mph slower when towing in 3rd on the interstates.

You bring interesting numbers. I just bought a new 4X4 2011 Silverado with 4.8L & 3.42 rear axle, and locked differential.

I tow an 18 boat which weighs approximately 3300lbs. I'd say 4500lbs loaded with gas & equipment. However, I bought the truck and the boat is still in storage. I'm sure you can understand that I can't wait to tow my boat and see the difference from the Blazer (4X4 4.3L) that I used to have.

I'm looking forward to see whether the transmission will be downshifting often. If it does, I'll just do like my Blazer and leave it in 3rd gear.

I have a couple of question that perhaps you can answer:

1- Do you believe the transmission will run that much hotter in 3rd gear versus Drive?

2- What would be an acceptable RPM for my 4.8L to run for approximately 200 miles?

Thanks in advance.

GPSilverado · April 10, 2011

I would think your mileage is pretty close. I tow a 23 foot Grady White boat, which weighs in around 6500 - 7000 lbs when loaded and ready for fishing including trailer weight. My truck came with 3.42 gears, and I towed in 3rd. It took me a full tank (20 - 21 gallons useable) to go to a lake 2 hrs away and back. Actual mileage has always been calculated at 9-10 mpg driving 55 -65. Going to another lake, just a bit less distance, but with Interstate most of the way, I was geting the same results on the tank of fuel, but mileage was down to 8 -9 mpg while running anywhere from 60 -70 mph, but also encountering inclines that were more pronounced, with less flat stretches of road. My rpm's were usually 2400 - 2700 with the 3.42 gears.

Changing to 4.10 gears actually helped the fuel mileage, and now I use about 1.5 - 2 gallons less on the trip not traveling the interstate, still in 3rd, but at 2500 - 2800 rpm's. The Interstate trips are almost the same, but if I use 3rd, I am at 2700 - 3100 rpm's, so I find myself using Drive more often, which actually uses more fuel, but turns less rpm's. Drive puts the engine below the torque range, and works the engine much harder even though it is turning less rpm's.

I have found that if I can drive around 60mph, in 3rd, I get the best mileage when towing due to less drag from the wind, but increasing the rpm's into the 2600 - 2700 range for more efficient power.

In your situation, you have a much larger wind drag, so lower speed may help, but IMO, I would always want the engine turning somewhere around 2500 rpm for best results.

On a side note, I think the 3.73 would be the best gear for the 4spd trucks with stock tire sizes, since 3rd is still turning an acceptable amount of rpms at highway speeds. I LOVE the 4.10 gears, but I feel the need to drive about 5 mph slower when towing in 3rd on the interstates.

You bring interesting numbers. I just bought a new 4X4 2011 Silverado with 4.8L & 3.42 rear axle, and locked differential.

I tow an 18 boat which weighs approximately 3300lbs. I'd say 4500lbs loaded with gas & equipment. However, I bought the truck and the boat is still in storage. I'm sure you can understand that I can't wait to tow my boat and see the difference from the Blazer (4X4 4.3L) that I used to have.

I'm looking forward to see whether the transmission will be downshifting often. If it does, I'll just do like my Blazer and leave it in 3rd gear.

I have a couple of question that perhaps you can answer:

1- Do you believe the transmission will run that much hotter in 3rd gear versus Drive?

2- What would be an acceptable RPM for my 4.8L to run for approximately 200 miles?

Thanks in advance.

I may be wrong, but I think the transmission will not run any warmer in 3rd than in drive. MIne never runs over 190F but I do have the trans cooler than comes with the HD trailering package.

I think with a 3.42, you'll be fine in 3rd at any reasonable speed you want to drive. Keep it under 75mph, and you'll be fine. I wouldn't want to turn more than 2800 rpm for that length of time, but it would be OK even at 3000 rpms. These engines do great at the higher rpm's when compared to the 4.3 and 5.7 of old.

502ci · April 10, 2011

I agree sound about right. My 2006 5.3 Sierra with a 3.42 gear gets 9 to 10 mpg (depending on the hills) towing a 24 ft. enclosed trailer weighing 8,000 lbs. loaded. It does have a V-nose which seems to help.

bartonjude · April 11, 2011

I have a 07 Classic CC with the 5.3L and 3.73 gears, normally get 16 mpg, but towing a 16' trailer with 3500# of atvs, it drops to 11-12 mpg driving 65 mph, flat land here. The wind drag is what's eating your lunch.

jtramsey · April 12, 2011

my 4.8 with 3.23 gets 12 to 13 towing 4000lbs.I rarely let it get over 2000rpms.

GMCanuck · April 12, 2011

Thanks for all the input guys - looks like I'l ljust have to suck it up (or let the truck suck it up, I guess).

I was talking to a couple of family members on the weekend to see what their trucks (Dodge Hemi and Silverado 5.2L) do pulling their trailers. Both had similar stories, but the best advice I was given - - - - to not look at the mileage computer while towing, just enjoy the holiday...

Seriously though, I guess I'll just keep an eye on this during this upcoming camping season and see what perameters (i.e. speed, RPM, etc.) the truck likes best and try and settle there.

Either way, thanks for setting my mind at ease...

chuckyager · April 28, 2011

Thanks for all the input guys - looks like I'l ljust have to suck it up (or let the truck suck it up, I guess).

I was talking to a couple of family members on the weekend to see what their trucks (Dodge Hemi and Silverado 5.2L) do pulling their trailers. Both had similar stories, but the best advice I was given - - - - to not look at the mileage computer while towing, just enjoy the holiday...

Seriously though, I guess I'll just keep an eye on this during this upcoming camping season and see what perameters (i.e. speed, RPM, etc.) the truck likes best and try and settle there.

Either way, thanks for setting my mind at ease...

I'm jealous...LOL! I have a NBS crew cab Z71 5.3 4-speed 4X4 w/ 3.73 gears and I am seeing a pretty consistent 6.5 mpg. I have LT headers, no cats, a vararam CAI, and a programmer on mine too. I admittedly run my truck like I don't have anything back there either. I pull a 35' travel trailer that weighs 7,500# dry. Add 5-6 people and all the necessary gear for a 3-4 day trip + running 5 over the speed limit and pushing it hard up the hills or into wind and you don't get much in the way of fuel mileage. I have to accept that if I want to keep up w the other people I have to run with that have big duramaxes, I'm going to have to learn to accept that I am going to get horriffic fuel mileage. The up side to this is that the truck really does handle it well considering that I am asking a lot more than this truck was probably intended to do!