I used to pull at 65mph because that was what the max rating was for ST tires. On the way back from a trip, the truck was having engine problems to I took it real easy to make it home. The max speed was 55mph and I accellerated VERY slow. It was only a 300 mile trip but the difference in the amount of gas left in the tank was shocking.
Now, I usually tow at 60 on the speedometer which turns out to be about 58 mph in the real world. I just stay in the right lane. I've been blown by by people towing rigs as big or bigger than mine and it doesn't bother me one bit. I actualy find it much more relaxing to be the slow guy in the right lane, especially since I stopped worrying about idiots merging without looking or getting up to speed. Eventually they do look and the look is often priceless.
AS far as the original question as I understand it: Due to the huge effect of wind resistance when towing a RV, slower with higher RPMs nets better gas milage than faster with lower RPMs. I try for slower with lower RPMs.
Odly enough, does anyone else find themselves scolding their truck in their heads when it shifts out of OD at the crest of an overpass?
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Towing with a 4.8 or 5.6 gas engine my guess speed makes a big difference. Towing with a diesel that has 300+ HP and 500 lbs of torque I doubt you can tell the difference between 55 and 68, I cant. The only difference I can tell is in the amount of shifting
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OhhWell wrote: I used to pull at 65mph because that was what the max rating was for ST tires. On the way back from a trip, the truck was having engine problems to I took it real easy to make it home. The max speed was 55mph and I accellerated VERY slow. It was only a 300 mile trip but the difference in the amount of gas left in the tank was shocking.
Now, I usually tow at 60 on the speedometer which turns out to be about 58 mph in the real world. I just stay in the right lane. I've been blown by by people towing rigs as big or bigger than mine and it doesn't bother me one bit. I actualy find it much more relaxing to be the slow guy in the right lane, especially since I stopped worrying about idiots merging without looking or getting up to speed. Eventually they do look and the look is often priceless.
AS far as the original question as I understand it: Due to the huge effect of wind resistance when towing a RV, slower with higher RPMs nets better gas milage than faster with lower RPMs. I try for slower with lower RPMs.
Odly enough, does anyone else find themselves scolding their truck in their heads when it shifts out of OD at the crest of an overpass?
No scolding here.
Towing on flat land or hills low rpm"s are fine but when you are cilmbing 3-6 percent passes higher rpm = better economy and lower egt's.
I am in third gear around 2,800 rpm on the 6 percent passes at 55 mph.
Do not lug a diesel!
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Quote: About the sweet spot myth, I would challenge anyone with any vehicle to drive 1000 miles at 70 and 1000 miles at 55 and compare the MPG or you can choose slightly different speeds as long as they are far enough apart to really measure a difference. The low speed is always going to win as long as it isn't so low as to drop the trans down out of the top gear. I think people think their engine has a "sweet spot" because they are used to driving at a certain RPM range and like the way the engine sounds. If they slow down, the engine may seem to "lug" a little so the thought is that it will use more fuel. I don't think so. I don't think you will get better MPG at 65 than you would at 62 or 60 but the difference might be difficult to measure.
As a gasser driver I say get a Scanguage, you will quickly discover there are sweet spots. They can certainly change due to terrain/wind, but they definitely exist. On flatland stretches (we live in IL) our setup gets worse mpg at around 48mph than 55 mph. And I get worse mpg at around 58mph than I do at 63mph. I generally drive around 63, depending on terrain and wind. I would say get very familiar with your setup to get the best out of it.
We bought a used 2002 Coachmen 249. I have a 2004 F150 5.4L. Right after we bought the camper we did a "test" run to find out what it needed and most importantly to do a fuel mileage run.
This is in Florida, end of June. Trip was 310 miles each direction, using the exact same route. We left at the same time of day and weather conditions were almost exactly the same going and coming. Weight was essentially the same.
Driving with cruise control exclusively set at 65 we got 9.8mpg. Return trip, driving without CC, doing slow manual gas pedal control and running at 55 mileage went up to 12.1. I was hoping for a 10% differential, 20%+ amazed me.
We are getting ready to do a 10,000 mile run around the US and that kind of mileage differential is substantial. We have now put new tires on both trailer and TV (thankfully we actually made it back, as 2 trailer tires were starting to separate upon return), new bearings, new brakes and added a raised topper to the truck bed, so will be interested to see if any changes happen now. Hopefully, for the best.
daveesl wrote: We bought a used 2002 Coachmen 249. I have a 2004 F150 5.4L. Right after we bought the camper we did a "test" run to find out what it needed and most importantly to do a fuel mileage run.
This is in Florida, end of June. Trip was 310 miles each direction, using the exact same route. We left at the same time of day and weather conditions were almost exactly the same going and coming. Weight was essentially the same.
Driving with cruise control exclusively set at 65 we got 9.8mpg. Return trip, driving without CC, doing slow manual gas pedal control and running at 55 mileage went up to 12.1. I was hoping for a 10% differential, 20%+ amazed me.
We are getting ready to do a 10,000 mile run around the US and that kind of mileage differential is substantial. We have now put new tires on both trailer and TV (thankfully we actually made it back, as 2 trailer tires were starting to separate upon return), new bearings, new brakes and added a raised topper to the truck bed, so will be interested to see if any changes happen now. Hopefully, for the best.
dave
A test like this is probably not accurate.
Small elevation changes can make a big difference and wind direction even more.
Enough room for error to completely wipe out the advantage that you experienced, and even reverse it some.
Not saying that your test is 100% faulty, but I would not bet a paycheck on it.
For example. Going from Phoenix to Tucson, Empty my truck gets about
19 MPG. The return trip about 22 MPG. Done this trip many times, and this is the norm.
This trip appears flat. But there is a small gradual elevation change that causes the MPG difference. Loaded, the difference would be even more signifignant.
Huntindog
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To some extent the exact gear you run will not affect your mileage much (In high gear, you burn more gas to generate more pressure in the cylinders, while if you drop down one gear you need less gas for pressure, but more gas to deal with more engine displacement as the engine spins faster.)
...and to some extent mileage is 'all' about drag- if you want better mileage, you should go slower- period.
For these two reasons, one would have an argument that the sweet spot is something of a myth.
...now, that being said, with a typical TV you would not want to make your trip at 5 mph in first gear- that is outside (way outside) of the sweet spot...
Yes, there is a sweet spot- and it depends, it depends on your engine, your gears, your wind resistance...but if you really, really want to have better gas mileage, you could custom build a smaller motor and a different transmission where the sweet spot is 5 mph and save gas with the greatly reduced wind resistance.
If diesel I would say the "Sweet Spot" is where your EGT's & Boost are at thier lowest levels. Mine settles in to it's sweet spot at about 62 MPH indicated, but at 60 MPH the EGT is actually a little bit higher as well as the boost.
Huntindog wrote: 75MPH. Life is short and I'm busy. Got things to see and people to do.
You're right. Life is too short to put others at risk. What makes you think that your driving skills and equipment are so far superior to the standards and limits?
LOL. In AZ 75MPH IS the limit. And it is my standard. I drive in the high speed lane with the flow of traffic.
I am Canadian, and just towed accross the US. 6000 miles. I agree with his prior statement that going 55 is a far greater hazard on the interstate. 90% of the traffic is around 75, 55 is a rolling obstacle. I would have loved to travel 60, even that was dicey. People closing at 80, side by side, trying to find the passing lane before rear ending me, semi's passing, etc. To ignore the median speed of traffic and how a person towing fits into that is assinine. 2 vehicles going the same speed rarely crash. I settled on 70 mph, as that seemed like a good, safe comprimise.
And all this whining about trailer tires being rated for 65. Right.
Trailer tires are flex resistant heavy duty tires, have a far larger tolerance band than passenger care tires. Properly inflated trailer tires on good condition should not fail purely on account of speed.
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