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Old 11-14-2022, 07:15 AM   #1
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Running high RPMs for long periods

I tow a small TT (18' total length, 3,300 lb GVWR) with a mid-sized crossover (2010 Toyota Highlander SE, 3.5L V6, AWD, tow package rated for up to 5,000 lbs towing). My TV has a 5 speed automatic transmission. When towing, I lock it out of 5th gear such that 4th is my highest gear (otherwise it would hunt constantly).

On flat roads with little or no wind, I can cruise along at 65 mph in 4th gear turning around 2,800-2,900 RPMs. No problem. But throw in rolling hills, a modest headwind, or even a long, slight grade, and it's either hunting between 3rd and 4th gear, or staying mostly in 3rd gear. I can end up driving for long stretches turning around 4,000 RPMs in an attempt to maintain a reasonable highway speed. I'm not talking major mountain passes; everybody expects to slow down/gear down for those. I'm just talking garden variety hills and grades.

As an example, we did a cross-country trip this past summer. One stretch of highway that we traveled was from Thermopolis to Meeteetse, WY. No big mountain passes, but it's mostly uphill, with lots of small rolling grades, and there was a pretty stiff wind blowing with the outside temp above 90F. I drove 50 miles in about an hour with the car turning 4,000+ rpms in 3rd gear most of the time (not close to redline, which is about 6,400 rpms). The engine temp gauge stayed well within the normal range, though I could feel lots of heat coming out of the engine/trans compartment when we stopped. That was probably the worst stretch of the trip, but there were many other segments when the car spent extended periods of time turning high RPMs in 3rd gear.

I have a notion that it is not a good practice to do that type of driving on a regular basis, though I don't really have any objective information to back up that notion. My thinking is that most cars and light trucks are designed for carrying modest loads at highway speeds in high gear while turning around 2,000-2,500 RPMs. Yes, they're capable of turning much higher RPMs, but that usually happens in quick, short bursts (e.g., passing or merging on to the interstate).

My highway gas mileage when not towing is about 22 mpg, but towing drops it to around 9.5 mpg. So it's using 2.3 times as much gas when towing, which translates to putting 2.3 times as much energy through the drive train. I'm thinking that has to equate to increased wear and tear on drive train components, leading to a significantly shorter lifespan of those components. Aside from that issue, it makes for a very tiring drive day when my TV is struggling to maintain speed the whole time.

But I hear lots of folks on forums and Facebook groups say it's no big deal to run smaller engines at high RPMs for a long time. They say the engines are designed to run that way. And I have to concede that my car did not blow up on this 4,000 mile trip.

So I'll ask the towing experts here, am I putting my vehicle's longevity at risk, or am I just exhibiting a personal preference for an easier towing experience?
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Old 11-14-2022, 07:33 AM   #2
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2010 was a good year for the Toyota Highlander. It should last 250,000 miles easy. That is, unless you beat it up which you are doing by towing with it. It would be better if you camped at the local State Parks. But no - you want to tow cross country. The Toyota Highlander really is not made for that.

The Toyota Highlander is a people mover that you can tow a little bit with. Keep local and the Highlander will last longer. Running high RPM's will wear out an engine.
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Old 11-14-2022, 07:39 AM   #3
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Towing anything shortens the vehicles engine/drive train built in mfg duty cycle life span.
Even a 450 hp/1200 torque new LDT diesel truck.

Just a fact of life when we put a hitch on our tow vehicles.

Listening to a high rpm engine noise doesn't bother some folks but does others. I'm with the "others" crowd so I drive a diesel with lots of low end grunt for pulling various size trailers from 3k up to 16k gross weight.
I do't like noise anymore.
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Old 11-14-2022, 08:03 AM   #4
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Whether your using a grunting low RPM diesel or a high reving gas engine, engine life is guaged by % of HP used. Ask for more power, expect shorter life.

Commercial engines have charts and ratings that demonstrate engine life based on % of HP used.
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Old 11-14-2022, 08:10 AM   #5
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Sort of in the same boat. Silverado with a 4.8 towing within capacity but at the higher end. It drops out of 4th on a long overpass and the revs are above 4000. My current strategy is drop 2 mph when revs hit 4300. It shifts and if the load is still too much drop another 2 mph. This keeps me going at 58 to 65 in almost all cases. Oil pressure and all temps never get higher than acceptable parameters. My mpg is 16 empty, 11 loaded. I did an oil analysis this year and got excellent numbers, no metal or any signs of oil breakdown even after going 10K on the oil when normal is 5K. Not going with a bigger camper on this truck or heading to the rockies but I am comfortable with the motor working hard on the hills.
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Old 11-14-2022, 09:36 AM   #6
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Tow vehicle

I towed a bigger camper for a couple of years with a 2016 Chevy Colorado Z71. It had a similar engine, the Chevy 3.5L, V6, 305 HP but with a 6 speed transmission. The Colorado had a tow package (external transmission & oil cooler) and a “Tow Haul” mode for the transmission.
The tow haul mode adjusts the transmission shift schedule when trailering, so the engine is not constantly hunting for that next gear when towing.

It worked but I had the same concerns. The transmission would shift down, there was a significant increase in rpm‘s and suffering gas mileage.
Not towing was 22mpg, towing was 10….. In addition, it was just not a comfortable drive when towing.

Last year (Nov 2021) I made the decision to upgrade my tow vehicle. I purchased a 2022 Ram 1500 Big Horn with 3.92 towing gears in the rear end. It has the 5.7L V8 HEMI Engine with an 8-speed transmission and the tow package.

Yes, it is a much bigger truck however, I do not regret the purchase and do not experience any of the concerns discussed. Towing gas mileage is better than the Colorado. I am getting 11 to 12+ mpg. Not towing is 18+ mpg. The towing mileage is better because the engine and transmission are not working anywhere near as hard as the Colorado.

Not all of us are in a position to purchase the tow vehicle we truly need. However, in your case I think you are asking a lot from your Highlander.


I hope my opinion helps…
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Old 11-14-2022, 09:51 AM   #7
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I'm guessing you're over the trailer frontal sq,ft specs. Most auto manufacturers have a max trailer frontal sq.ft dimension that determines the tow vehicle requirements. i.e rear gearing, tow package, engine size, etc.
You have the HP and TQ for the weight of the TT and it shouldn't be an issue towing where you're towing so my guess is the frontal area is being exceeded and thats whats causing your issues.
I could be wrong of course but just basing my opinion on when I towed a 22' 4050 lb TT that was only 7' wide with an 06 Frontier V6. Less HP than you and a little more weight but I struggled all the time. The clincher was at around 65 mph I couldn't accelerate because the V6 was out of grunt. Probably because of the frontal area being exceeded.
I moved up to a 2010 F150 5.4 3.73 and it was as if there was no TT back there. Exaggerating of course but that's how it felt most of the time.
MPG's went from 8.9-9 up to 10.5-11. Less work by the bigger engine.
Not much you can do except do go where the TV will struggle or get a more powerful TV.
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Old 11-14-2022, 10:15 AM   #8
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Not running at Redline
Oil pressure good/steady
Cooling temps good, not overheating

Enjoy your camping trips


Increase your oil/filter changes
Check transmission fluids ....change earlier then routine schedule
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Old 11-14-2022, 10:47 AM   #9
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Quote:
Originally Posted by Old-Biscuit View Post
Not running at Redline
Oil pressure good/steady
Cooling temps good, not overheating

Enjoy your camping trips


Increase your oil/filter changes
Check transmission fluids ....change earlier then routine schedule
This.

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Old 11-14-2022, 10:59 AM   #10
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Quote:
Originally Posted by tuffr2 View Post
2010 was a good year for the Toyota Highlander. It should last 250,000 miles easy. That is, unless you beat it up which you are doing by towing with it. It would be better if you camped at the local State Parks. But no - you want to tow cross country. The Toyota Highlander really is not made for that.

The Toyota Highlander is a people mover that you can tow a little bit with. Keep local and the Highlander will last longer. Running high RPM's will wear out an engine.
Yeah, if money were no object, I would have already traded for a 1/2 ton pickup.
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Old 11-14-2022, 11:01 AM   #11
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Quote:
Originally Posted by twinboat View Post
Whether your using a grunting low RPM diesel or a high reving gas engine, engine life is guaged by % of HP used. Ask for more power, expect shorter life.

Commercial engines have charts and ratings that demonstrate engine life based on % of HP used.
This is kinda what I was thinking. The Highlander generates max torque/HP and around 4,200 RPMs, so when I'm running in third gear I'm using pretty much 100%.
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Old 11-14-2022, 11:03 AM   #12
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Quote:
Originally Posted by Cumminsfan View Post
I'm guessing you're over the trailer frontal sq,ft specs. Most auto manufacturers have a max trailer frontal sq.ft dimension that determines the tow vehicle requirements. i.e rear gearing, tow package, engine size, etc.
You have the HP and TQ for the weight of the TT and it shouldn't be an issue towing where you're towing so my guess is the frontal area is being exceeded and thats whats causing your issues.
I could be wrong of course but just basing my opinion on when I towed a 22' 4050 lb TT that was only 7' wide with an 06 Frontier V6. Less HP than you and a little more weight but I struggled all the time. The clincher was at around 65 mph I couldn't accelerate because the V6 was out of grunt. Probably because of the frontal area being exceeded.
I moved up to a 2010 F150 5.4 3.73 and it was as if there was no TT back there. Exaggerating of course but that's how it felt most of the time.
MPG's went from 8.9-9 up to 10.5-11. Less work by the bigger engine.
Not much you can do except do go where the TV will struggle or get a more powerful TV.
Owner's manual does not mention any frontal area specs, but yes, I'm pretty sure air resistance is a big part of the issue. When I'm driving in a headwind, pushing the accelerator further gets me nothing.
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Old 11-14-2022, 11:06 AM   #13
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Originally Posted by Old-Biscuit View Post
Not running at Redline
Oil pressure good/steady
Cooling temps good, not overheating

Enjoy your camping trips


Increase your oil/filter changes
Check transmission fluids ....change earlier then routine schedule
I'm in a Facebook group related to the Bushwhacker trailers, and this is the opinion that I hear from many in that group. Mostly folks like me who are towing with a CUV. Some of those guys are even towing with turbo 4 cylinders.

I do keep up with the extra fluid changes that are specified for towing.
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Old 11-14-2022, 11:09 AM   #14
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I tried towing with a 3.5 V6 Honda Ridgeline 5 speed. That thing sucked gasoline at 9 mpg. I traded for a F-150 5.0 V8 6 speed. I got 10.5 mpg towing the same exact travel trailer. IMHO a V6 engine was working harder.

Towing into a wind with a V6 engine is nearly impossible with the frontal area of the travel trailer. Like towing a big box.

Change oil a lot sooner and use synthetic oil with more 'slippy' in it.
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