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#4453712 - 07/08/17 07:17 PM Thicker oil for hotter ambient temp, Why?
David_g Offline


Registered: 07/22/11
Posts: 143
Loc: California
It's common for manufacturers to recommend thicker oil for higher ambient temperature. But if the coolant temperature gauge says the bike isn't running hotter, why different oil? Does the engine have hotter operating conditions in some way not indicated by coolant temperature? Or in the case of my air/oil cooled BMW temperature of whatever the dash indicator is measuring.

I wonder because temps have been high here lately (38+ C, 100+ F). And for the CRF1000L I just changed the oil on, the only recommended grade is 10W30. Yet on the africa twin forums some owner report that their local dealers use or recommend 40 instead of 30. In one case due to the tropical conditions there.

I continued to put 10W30 in it. But I wonder if I'm making a mistake. I still haven't completely wrapped my mind around 10W30 being sufficient to lubricate a gearbox. DCT in this case.
_________________________
2007 BMW R1200R (Mobil 1 15W50, Red Line Shockproof Heavy, Supertech 75W90)
2016 Honda Africa Twin DCT (Motul 5100 10W40)

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#4453724 - 07/08/17 07:31 PM Re: Thicker oil for hotter ambient temp, Why? [Re: David_g]
Kuato Offline


Registered: 10/23/05
Posts: 7094
Loc: Colorado
Higher temps mean the possibility of thinning oil, seems like the manufacturer is putting the thicker oil recommendation to insure sufficient viscosity. Even though the gauge shows temps are cool, there could be hotter spots somewhere away from the sensor where the oil is hotter and therefore thinner.
_________________________
Thick vs Thin test: 15k / 43k miles complete

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#4453736 - 07/08/17 07:43 PM Re: Thicker oil for hotter ambient temp, Why? [Re: David_g]
Syntheticuser Offline


Registered: 06/11/17
Posts: 147
Loc: Waco, Tx.
I agree Kuato. However, I have run everything from 0w20 to 5w40 in my Zetec Focus. It runs fine on anything I feed it. Only use synthetic. I have seen a 7* temperature drop using 0w20 Magnatec vs 0w40 BC. Odd that the thinner stuff lowers oil temps.

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#4453745 - 07/08/17 07:56 PM Re: Thicker oil for hotter ambient temp, Why? [Re: Syntheticuser]
Shannow Offline


Registered: 12/12/02
Posts: 39835
Loc: 'Stralia
Originally Posted By: Syntheticuser
I agree Kuato. However, I have run everything from 0w20 to 5w40 in my Zetec Focus. It runs fine on anything I feed it. Only use synthetic. I have seen a 7* temperature drop using 0w20 Magnatec vs 0w40 BC. Odd that the thinner stuff lowers oil temps.


Not really odd...the majority of the oil temperature rise in service is due to the viscous shearing of the oil in bearing surfaces - by bearing surfaces, not just bearings, but piston skirts and the like too.

Here's modelling of a big end...as you can see, the power wastage lessens with decreasing viscosity...and similarly the RPM variance.


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#4453814 - 07/08/17 09:25 PM Re: Thicker oil for hotter ambient temp, Why? [Re: David_g]
jeff78 Offline


Registered: 06/06/17
Posts: 129
Loc: New York
Originally Posted By: David_g
It's common for manufacturers to recommend thicker oil for higher ambient temperature. But if the coolant temperature gauge says the bike isn't running hotter, why different oil? Does the engine have hotter operating conditions in some way not indicated by coolant temperature? Or in the case of my air/oil cooled BMW temperature of whatever the dash indicator is measuring.


Coolant temperature indicates temperature of the coolant, which isn't necessarily an accurate indication of oil temperature. It's a good bet that somewhere inside the engine (in the bearings, for example), localized oil temps will be higher than the coolant temp.

I installed an aftermarket oil temp gauge (Trail Tech) on my bike - the sender is just downstream of the oil/coolant heat exchanger. As one would expect, the oil temperature tries to 'chase' coolant temperature. But I know that the indicated oil temperature at this point is going to be the lowest it's ever going to be, since it's right after the oil has gone through the oil cooler.

Hotter oil is thinner so you lose a little bit of that safety margin between metal-metal in bearings and such.


Quote:
I wonder because temps have been high here lately (38+ C, 100+ F). And for the CRF1000L I just changed the oil on, the only recommended grade is 10W30. Yet on the africa twin forums some owner report that their local dealers use or recommend 40 instead of 30. In one case due to the tropical conditions there.


AFAIK, strangely Honda is the only one of the Big Four Japanese m/c manufacturers to recommend 10W-30 across most (if not all) of their lineup for the past several years. The Other Three typically recommend 10W-40, with allowances for different viscosity grades depending on ambient temps.


Quote:
I continued to put 10W30 in it. But I wonder if I'm making a mistake. I still haven't completely wrapped my mind around 10W30 being sufficient to lubricate a gearbox. DCT in this case.


You can give a xxW-40 a try at your next oil change and see how you like it. The worst that could happen is that the bike might run a little hotter or you don't like how the oil feels for whatever reason.

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#4453870 - 07/08/17 10:27 PM Re: Thicker oil for hotter ambient temp, Why? [Re: David_g]
David_g Offline


Registered: 07/22/11
Posts: 143
Loc: California
Thanks! I think this time I would have used 10W40 if I'd had enough of one single variety in my garage. I did have enough 15W40, but I'm not eager to be the first (that I know of) to use that in a DCT.

_________________________
2007 BMW R1200R (Mobil 1 15W50, Red Line Shockproof Heavy, Supertech 75W90)
2016 Honda Africa Twin DCT (Motul 5100 10W40)

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#4453882 - 07/08/17 10:45 PM Re: Thicker oil for hotter ambient temp, Why? [Re: David_g]
oldhp Offline


Registered: 06/28/12
Posts: 1621
Loc: USA
My Challenger R/T oil temp runs 10-15(198-205'ish) hotter when it's over 90 even though water temp stays the same(196-200) This past winter it almost never got over 195.
_________________________


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#4454125 - 07/09/17 09:18 AM Re: Thicker oil for hotter ambient temp, Why? [Re: David_g]
alarmguy Offline


Registered: 07/10/12
Posts: 2147
Loc: South Carolina
You cant go wrong if using the oil recommended by your owners manual, at the same time I agree with what dealers do with friends bikes by using a 10/40 in 100 degree tropical conditions. Bottom line it will not hurt anything even in subtropical conditions.
Oil recommendations are based on an "average" ... your riding temps are way above average. Some manuals give you options other company manuals do not.
Your oil will run hotter for sure, doesnt matter about liquid cooling.

Either way, 30 or 40 you are good to go, me personally, living in a place with HOT daytime temps for 4+ months a year I always lean to the higher viscosity and if I lived up north I would lean towards the lower..

One other point, in those temps it doesnt matter if it is 10/40 or 15/40 but since you are not even sure that you want to run a 40, then I would suggest the 10/40 if you do.
_________________________
14 Road King (current)
08 VStar 1300 Tourer
07 Suzuki C50

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#4454127 - 07/09/17 09:20 AM Re: Thicker oil for hotter ambient temp, Why? [Re: David_g]
LoneRanger Offline


Registered: 07/02/07
Posts: 4047
Loc: Midwest USA
Definitely want to err in favor of the higher vis choice in the heat. My 2013 Ducati the manual showed no upper temp limit on 10W40 same as 15W50 on the page that had the viscosity charts. But once I heard how much extra clatter was coming from the already notorious-for-noise desmo valvetrain on 10W40 in summer, I switched it to 15W50 and never went back.
_________________________

'09 Subaru Forester ...................(QSED DEXOS1 5W30)
'16 Moto Guzzi Stelvio 1200 .....(ENI i-Ride PG 10W60)

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#4454129 - 07/09/17 09:21 AM Re: Thicker oil for hotter ambient temp, Why? [Re: oldhp]
Astro14 Offline


Registered: 10/10/10
Posts: 8525
Loc: Virginia Beach
Originally Posted By: oldhp
My Challenger R/T oil temp runs 10-15(198-205'ish) hotter when it's over 90 even though water temp stays the same(196-200) This past winter it almost never got over 195.


Exactly.

Oil temp is related to coolant temp, but in hot weather, or under severe load, the oil temp can vary well above coolant temp. So, to hedge their bets, OEMs specify a higher viscosity in anticipation of those higher oil temps.
_________________________
32 Packard 15W40
02 Volvo V70 T5 0W40 M1
02 Volvo V70 XC 0W40 Edge
05 MB S600 0W40 M1
16 Tundra 1794 5W30 Valvoline

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#4454136 - 07/09/17 09:29 AM Re: Thicker oil for hotter ambient temp, Why? [Re: oldhp]
Kuato Offline


Registered: 10/23/05
Posts: 7094
Loc: Colorado
Originally Posted By: oldhp
My Challenger R/T oil temp runs 10-15(198-205'ish) hotter when it's over 90 even though water temp stays the same(196-200) This past winter it almost never got over 195.


Thanks!! This is exactly the kind of data that backs up what we've us "thick oil guys" have been saying, namely that in some conditions, a thicker oil will offer more protection. Not necessarily all the time, but under a load in hot temps I'll go thick, thanks.
_________________________
Thick vs Thin test: 15k / 43k miles complete

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#4454192 - 07/09/17 10:55 AM Re: Thicker oil for hotter ambient temp, Why? [Re: David_g]
igs Offline


Registered: 11/29/16
Posts: 51
Loc: CA
The question isn't why thicker oil for hotter ambient temp. The question is why thinner oil for colder ambient temp. And the answer to that is flow.

You should be running the thickest oil for your temperature region where the oil will still flow when cold for maximum engine protection.

The only other reason to run a thinner oil is CAFE which does not benefit you the individual owner at all.
_________________________
2018 Honda J35Y6 | Walmart SuperTech 20W50 Summer | Chevron Supreme 5W30 Winter | 6 Month OCI

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#4454247 - 07/09/17 12:44 PM Re: Thicker oil for hotter ambient temp, Why? [Re: Kuato]
Astro14 Offline


Registered: 10/10/10
Posts: 8525
Loc: Virginia Beach
Originally Posted By: Kuato
Originally Posted By: oldhp
My Challenger R/T oil temp runs 10-15(198-205'ish) hotter when it's over 90 even though water temp stays the same(196-200) This past winter it almost never got over 195.


Thanks!! This is exactly the kind of data that backs up what we've us "thick oil guys" have been saying, namely that in some conditions, a thicker oil will offer more protection. Not necessarily all the time, but under a load in hot temps I'll go thick, thanks.


Having an oil temp gauge on my old Volvo turbo was an education. There was a separate, thermostatically controlled, oil cooler. Thermo opened at 70C, and the engine took a long time to reach 70C oil temp in the winter. Often, if gently driven, it never would. In the summer, it would climb to full opening temp of 85C quite quickly.

In either case, turbo load (and therefore, heat) on the turbo would rapidly warm the oil. The turbo was water cooled, so the oil wasn't the only thing cooling it, but it sure put a lot of heat into the oil. On a warm day, or driving in the Colorado mountains (lot of time at full boost), it would climb up to 105C, sometimes, if it was both hot and being pushed hard, I would see 110-115C.

This was the pan temperature, so, at some places in the engine, I am certain that the oil was even warmer. While I appreciate the oil pressure gauge (when it works, and isn't damped to be another idiot light), and I can impute oil temp from idle oil pressure with an accurate gauge, I do wish that all cars came instrumented with an oil temp and transmission oil temp gauge.
_________________________
32 Packard 15W40
02 Volvo V70 T5 0W40 M1
02 Volvo V70 XC 0W40 Edge
05 MB S600 0W40 M1
16 Tundra 1794 5W30 Valvoline

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#4454568 - 07/09/17 06:49 PM Re: Thicker oil for hotter ambient temp, Why? [Re: igs]
David_g Offline


Registered: 07/22/11
Posts: 143
Loc: California
Originally Posted By: igs
The only other reason to run a thinner oil is CAFE which does not benefit you the individual owner at all.

Do you think that's Honda's motivation for specifying 30? I didn't think CAFE applied to motorcycles.

Never owned a Honda car, but I think they spec thinner than typical in cars too. Modern cars I've owned specify 30, and from what I've read Honda specifies 20.
_________________________
2007 BMW R1200R (Mobil 1 15W50, Red Line Shockproof Heavy, Supertech 75W90)
2016 Honda Africa Twin DCT (Motul 5100 10W40)

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#4454858 - 07/10/17 12:00 AM Re: Thicker oil for hotter ambient temp, Why? [Re: Kuato]
oldhp Offline


Registered: 06/28/12
Posts: 1621
Loc: USA
Originally Posted By: Kuato
Originally Posted By: oldhp
My Challenger R/T oil temp runs 10-15(198-205'ish) hotter when it's over 90 even though water temp stays the same(196-200) This past winter it almost never got over 195.


Thanks!! This is exactly the kind of data that backs up what we've us "thick oil guys" have been saying, namely that in some conditions, a thicker oil will offer more protection. Not necessarily all the time, but under a load in hot temps I'll go thick, thanks.


Had the R/T out today for over 3hrs just driving, 165 miles, 98 hot,humid AC on, oil temp ran 205-208....water temp stayed at 196 all day. cheers
_________________________


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