Running high RPMs for long periods

[twinboat]

Originally Posted by Wellibe

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%.

It's not just rpms that create HP and torque, throttle position is a big factor.
If you have the pedal to the floor and struggling to just turn 4200 RPMs then you are maxing out your HP. If at part throttle, no, you are below the maximum.

All dyno HP and torque graphs are recorded at wide open throttle.

[Marine359]

We have a comfortable tow with our 2021 3.6L gasser Canyon. The additional displacement and the new 8 speed transmission makes it suitable for long uphills and downhills without needing to run at high rpm. Rpm will run high on steep downhill in tow/haul mode as tranny allows you to downshift if you’re in low range. On very long steep grade downhills, we use turnouts to allow engine and tranny to cool for a few minutes. With about 12k miles towing across the entire country, no problems yet from engine or tranny. However, I will mention that our TT is only 7ft wide. I don’t think the Canyon would be suitable for a standard width TT. We get 22mpg not towing, and 11mpg towing. Not real happy with 4wd towing through snow deeper than one foot. Rear end tends to wander and slide. But that could be a function of tire type which isn’t aggressive tread.

[Wellibe]

Originally Posted by twinboat

It's not just rpms that create HP and torque, throttle position is a big factor.
If you have the pedal to the floor and struggling to just turn 4200 RPMs then you are maxing out your HP. If at part throttle, no, you are below the maximum.

All dyno HP and torque graphs are recorded at wide open throttle.

I'm not completely wide open. Maybe 2/3.

[Wellibe]

I should have mentioned height/width specs for my trailer. It is pretty small as TTs go, at 6'9" wide and 8'8" high. But still feels like pulling a boat anchor in the wind.

[Mudfrog]

Originally Posted by Old-Biscuit

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 agree, especially since we're talking about a Toyota here!

That is, as long as this is the only concern. It'd probably be better to get a stouter tow vehicle if those higher rpms bug you with the noise and/or make you uncomfortable.

[Old-Biscuit]

As they say
"Run what you brung"

[twinboat]

Originally Posted by Wellibe

I'm not completely wide open. Maybe 2/3.

Then your probably using about 60% to 75% of available HP.

Gas engine airplanes and gas engine boats recommend 60% to 75% power at cruising speed for long life.

[kdauto]

Originally Posted by Wellibe

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?

A Highlander is not the most robust towing platform, and you are likely right at the upper limit (the TRUE upper limit, not what the OEMs tout). It's FWD based, and most FWD based vehicles don't like excess heat for long periods.

A RWD based vehicle with its North-South oriented engine evacuates heat more evenly. The setup also typically allows more room for bigger and better cooling systems, including trans coolers and even PS coolers.

Your engine can tolerate 4000 RPM for hours on end, it really doesn't concern me. Heat is your enemy, and I'd suspect the transmission will go out before the engine does, unless the radiator or a hose busts first and you overheat it.

I run my much larger 6.0 gas at 5500 RPM for minutes at a time going up steep highway passes loaded. Coolant is replaced every 5 years and belts, t-stat and fan clucth are always in tip-top shape.

I'd recommend you don't beat on it too hard. That platform is good for 400 000km-500 000km easy without a trailer. Run it hard, you can cut that lifetime in 1/2. Do trans fluid using genuine WS fluid every 80 000km-100 000km tops, and engine oil at 50-60% of recommended interval if you tow for any appreciable distance.

[Wellibe]

Originally Posted by kdauto

A Highlander is not the most robust towing platform, and you are likely right at the upper limit (the TRUE upper limit, not what the OEMs tout). It's FWD based, and most FWD based vehicles don't like excess heat for long periods.

A RWD based vehicle with its North-South oriented engine evacuates heat more evenly. The setup also typically allows more room for bigger and better cooling systems, including trans coolers and even PS coolers.

Your engine can tolerate 4000 RPM for hours on end, it really doesn't concern me. Heat is your enemy, and I'd suspect the transmission will go out before the engine does, unless the radiator or a hose busts first and you overheat it.

I run my much larger 6.0 gas at 5500 RPM for minutes at a time going up steep highway passes loaded. Coolant is replaced every 5 years and belts, t-stat and fan clucth are always in tip-top shape.

I'd recommend you don't beat on it too hard. That platform is good for 400 000km-500 000km easy without a trailer. Run it hard, you can cut that lifetime in 1/2. Do trans fluid using genuine WS fluid every 80 000km-100 000km tops, and engine oil at 50-60% of recommended interval if you tow for any appreciable distance.

Thanks for the advice. The tow package includes a transmission cooler, engine oil cooler, larger engine radiator, and more powerful cooling fans. I just changed coolant this past spring and don't intend to let it go more than 5 yrs/50,000 mi. I did two drain and fills on the transmission when I first started towing, and am intending to do a single drain and fill every 30,000 mi from here on out (owner's manual specifies 60,000 mi interval for towing). I'm also changing gear oil every 15,000 miles. Engine oil never goes more than 5,000 mi, and I only use name brand full synthetic.

I don't have a transmission temp gauge, so I can't really monitor the ups and downs of transmission temp. But the transmission cooler shares coolant with the engine radiator, so an overheating transmission should show up as increasing engine temp. So far the engine temp has never gotten past the middle of the normal range (it's an idiot gauge rather than an actual thermometer).

Currently the car only has 93,000 mi on it. If I continue long distance towing with it, I doubt I will keep it past 200,000 mi.

[CecilD]

The Toyota V6 at 3,500 RPM has the same piston speed as a 6.7 Cummins at 2,345 RPM. Dual overhead cams, 4 vales per cylinder, spin it up, probably better than lugging it.

I've always wondered which is better for fuel economy: Light throttle and high RPMs or heavy throttle and low RPMs.

[Wellibe]

Originally Posted by CecilD

The Toyota V6 at 3,500 RPM has the same piston speed as a 6.7 Cummins at 2,345 RPM. Dual overhead cams, 4 vales per cylinder, spin it up, probably better than lugging it.

I've always wondered which is better for fuel economy: Light throttle and high RPMs or heavy throttle and low RPMs.

I presume the slower piston speed is due to the shorter stroke? So more revolutions does not equal more wear on the wrist pins relative to a larger engine. But I'm guessing more revolutions equals more wear on the main bearings, rod bearings, camshaft bearings, VVT cam gears, timing chain, water pump, valve springs, etc.

I have heard it said that higher RPMs is better for the transmission than lugging at lower RPMs. Presumably due to faster circulation of the fluid, which cools it better.

[tuffr2]

There has to be more wear. You are pumping a lot more gasoline through the engine. I think the key is more synthetic oil changes. Use the extreme use oil change schedule also.

When I towed with a Honda Ridgeline I was worried about the weak Honda transmissions. Honda is not known for building sturdy automatic transmissions.

Probably with a Toyota Highlander the transmission is the weak link. I would follow the fluid change interval on the transmission.

Good luck

[MCCOHENS]

Buy a scangage, which hooks to the OBD port and will read trans temps and 3 other parameters. If trans temps are high get an external cooler as the trans is probably more stressed than the motor. Information is your best friend.
Short story, a buddy years ago had a VW westy camper van. He insisted pulling his hobie 16 sailboat with it even though I advised not to. First trip after about 200 miles he blew a rod thru the case. We put in a used motor and installed a cylinder head temp gage. I told him when it hits 350 slow down, when it hits 375 slow down more. When it hits 400 pull over. He did that for years without an issue. Temps tell so much about how hard your vehicle is working.

[propchef]

Originally Posted by Wellibe

I presume the slower piston speed is due to the shorter stroke? So more revolutions does not equal more wear on the wrist pins relative to a larger engine. But I'm guessing more revolutions equals more wear on the main bearings, rod bearings, camshaft bearings, VVT cam gears, timing chain, water pump, valve springs, etc.

I have heard it said that higher RPMs is better for the transmission than lugging at lower RPMs. Presumably due to faster circulation of the fluid, which cools it better.

The higher RPMs keep you in the optimum working range of the motor. The V6 is a stout powerplant that will carry you many miles. Towing mode in many vehicles locks out overdrive and raises the shift points to take advantage of the power curve.

Buy a scangage, which hooks to the OBD port and will read trans temps and 3 other parameters.

^^this is good advice and the easiest way to keep up with temps. I'd also suggest sending a sample of the oil to Blackstone at every oil change. This gives you a good snapshot of the health of your motor.