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Discussion Starter #1
So I have always liked and mostly owned Subaru's. I have towed a fair amount of 17-24' campers, utility trailers, and enclosed trailers- ranging from a 03' forester 2.5 auto, 14' Honda ridgeline, 18' Highlander V6, and now my 15' outback.
Last week I had a local shop add a uhaul 2" hitch, and curt wiring adapter.
Yesterday I picked up a 12x6 v-nose aluminum enclosed trailer. It weighs about 900lbs empty (which it was), and has an interior height of about 6' (so a decent size front area, but not as big as campers).
I only had to go about 40 miles, 20 of which were fairly flat highway, last 20 were mild hills and 45-60mph.

I can't believe how hard my outback had to work to keep the car and trailer at 65/70 (70mph speed limit and average traffic was around 80mph)
The rpm's were around 3000 the whole highway, when normally under 2000. The car handled great on the highway and the smaller roads (turning, cross wind, braking etc).
I checked the vehicle info on the radio/screen, the oil temp was 225-235.

This was a huge disappointment because I was thinking of converting the trailer to a camper, or keeping for around the house projects- but I don't want to kill the subaru in doing so.

Has anyone had a similar experience?
(also- in april my 60k service was done including new brakes all around, so all fluids are fresh)

Thanks guys! (y)(y)
 

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At 65/70 mph, aerodynamic drag is a killer ... especially if your trailer is a big rectangular box. The 3,000 rpm is a result of the ECU and TCU (engine and CVT controllers respectively) choosing the most efficient throttle/rpm regime for the load.

Remember, aerodynamic drag varies as the square of airspeed (D ~ speed^2), but the horsepower required to overcome that drag varies as the cube of speed (P ~ speed^3). (For example, reducing your speed from 70 mph to 60 will reduce the power required due to drag by more than 1/3!) Also remember that a modest 10 mph headwind has the same effect on drag as driving 10 mph faster in no-wind conditions.

Based on my experience (2016 Outback 2.5), your engine oil temperature is within the normal range for highway cruising. I generally expect to see 220-230 F when cruising at 65 to 70 mph, hot day (90+ F), level ground, moderate load, no trailer.
 

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It's like pulling a parachute, try driving 60 mph. I pulled a lot of stuff with a 3/4 ton truck and trailers with frontal area can pull like trailers twice the weight, but reducing the speed can make a big difference.


Sent from my XT1254 using Tapatalk
 

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Honestly, 3000 rpm doesn't sound bad at all to me. 3800 might be concerning though. Many have said to drive by rpm with our CVTs vs by mph. That may help too. YMMV
 

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Discussion Starter #5
ammcinnis: good point: I haven't seen what a "normal" highway drive is like for temps. But good to know it sounds like I wasn't in the danger zone

hyper: I haven't tried pulling a parachute, but I can only imagine lol. But on a serious note, I can see where speed is a big factor (like you said). The back roads were fine at 45-60mph. I guess I'm just a little surprised that with a v-nose, and only 6' wide and about 6' tall- the effect it had.


2wheel: That's a good point about driving based off rpm, seeing as that's kind of how the cvt works (I know not exactly, but more than traditional gear box). Maybe I just need to adjust some to the cvt. I am used to 4,6,8 speed transmissions (forester, ridgeline, and highlander)
 

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I pull a 1200 lb camper around. It works hard trying to go 70-75, but I usually drive 65 at the most. Hills are a killer tho. That Cvt kicks down, rpms go up and that engine roars. I changed to royal purple and haven’t seen my oil temps over 250 since. Your results may vary. Not plugging RP. Just had some laying around from my truck.
 

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I ... haven’t seen my oil temps over 250 since.
One data point, FWIW: The highest engine oil temperature I've ever seen in our 2016 Outback 2.5 was 240, which it touched briefly following a steep 6.4% climb to the summit of Monarch Pass in Colorado (elevation 11,312 feet) on a hot day last month (August 2019). We weren't towing anything, though.
 

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FWIW, the highest engine oil temperature I've ever seen in our 2016 Outback 2.5 was 240, which it touched briefly following a steep climb to the summit of Monarch Pass in Colorado (elevation 11,312 feet) on a hot day last month (August 2019). We weren't towing anything, though.
I was @ 255F on the oil that came with mine when I bought it. (assuming Subaru oil) uphill, camper with headwind, 85F. Could have been higher but this was when I started watching.
 

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250 is to high you are pushing burning the oil and additives. - bad news
 

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250 is to high you are pushing burning the oil and additives. - bad news
At 250 F for short periods I would be more concerned about viscosity than volatility or oxidation. I would be very uncomfortable with sustained temperatures of 250+ for extended periods.

If someone regularly observes engine oil temperatures above 250 F, I would definitely recommend considering adding an external oil cooler.
 

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JMO, but I'd be hesitant to tow anything larger than a garden trailer with a CVT. Something about the whole thing running in shear condition rather than compression/tension like a geared trans. And, of course, the 200# tongue weight.
 

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Discussion Starter #13
I pull a 1200 lb camper around. It works hard trying to go 70-75, but I usually drive 65 at the most. Hills are a killer tho. That Cvt kicks down, rpms go up and that engine roars. I changed to royal purple and haven’t seen my oil temps over 250 since. Your results may vary. Not plugging RP. Just had some laying around from my truck.
I appreciate the insight. My old mechanic friend swore by royal purple, so I get it.
Sounds like we are experiencing similar weight and size (wind movement).

Reading bellow I can agree that 250F sounds hot, and maybe a trans cooler could be helpful (I read an article yesterday in the towing section about a guys adventure with a cooler and how much it improved temps.)
 

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JMO, but I'd be hesitant to tow anything larger than a garden trailer with a CVT. Something about the whole thing running in shear condition rather than compression/tension like a geared trans.
Please explain how you see it as shear condition. A linked belt to transfer power is in tension to me. What am I missing? Are you talking about the contact between the belt and cones?
 

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Are you talking about the contact between the belt and cones?
Yes. The belt grabs the sheaves using friction materials on the belt edges.
 

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I appreciate the insight. My old mechanic friend swore by royal purple, so I get it.
Sounds like we are experiencing similar weight and size (wind movement).

Reading bellow I can agree that 250F sounds hot, and maybe a trans cooler could be helpful (I read an article yesterday in the towing section about a guys adventure with a cooler and how much it improved temps.)
I put a trans cooler in also.
 

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Yes. The belt grabs the sheaves using friction materials on the belt edges.
Ok. But then isn't any disc clutch in contact with a pressure plate also in shear condition? Conventional automatic transmissions have clutch plates to engage/disengage each gear set in addition to the one in a lockup toque converter. Luckily, we no longer have auto transmissions that use bands (other than antique and vintage ones).
 

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Ok. But then isn't any disc clutch in contact with a pressure plate also in shear condition?
Yes, but with a far greater contact area.
 

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Please explain how you see it as shear condition ...Are you talking about the contact between the belt and cones?
Yes. The belt grabs the sheaves using friction materials on the belt edges.
Only partially correct. First, the Variator uses a chain, not a belt, and there is no direct metal-to-metal contact. Second, there are no "friction materials" involved. Both the Variator cone faces and the chain's "feet" are highly finished, hardened steel; per Subaru, the contact pressure between cone and chain feet can reach an astounding 145,000 psi, depending on engine load. (Source: Subaru Technician Reference Booklet MSA5P1475C, June 2014, page 25 ... available for download from the STIS web site.) The two most critical requirements of the CVT fluid are 1) to provide adequate film strength to prevent metal-to-metal contact between the cone and chain feet under all circumstances, and 2) to transmit 100% of the motive force through the fluid film separating the cone and chain feet, in shear, without slipping.

N.B. 145,000 psi exceeds the yield strength of most low-grade steels! A Variator with cones and chain made of mild steel would chew itself up in minutes.
 
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