I was wondering whether oil weight has a significant or measureable effect on engine cooling. For example, many people run 20w50 in bikes that recommend 10w40 oil. Theoretically, this should provide higher oil pressure but lower flow volume. Does the lower flow volume make the engine run a bit hotter? Especially on oil cooled engines which rely on the flow rate of the oil for cooling, it seems this could happen.
oil weight vs. cooling
- Thread starter MRC01
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Well i can say what happened to me on this subject.. In my 1994 honda cb750Nh i always ran mobil1 10w30 with great results. then i decided to try their 15w50. and my bike hated it!! my valves were hydralic and used the engine oil to self adjust themselves. and then valves got extremely noisey and then engine got very very hot. It got so hot i was afraid. and went back home to see what was wrong. btw the engine was a AIR-cooled scooter. so i then drained the oil and went back to mobil1 10w30 and all was fine once again. No valve noise and the engine was running cool as always! ALSO... the engine had a small factory installed oil cooler on the front of it... My theory is, it you have a modern motorcycle why would you need 15w50 20w50? i have a 2002 kawasaki vulcan 800 classic, and i use amsoil 10w40 motorscooter oil in it. and it runs great! i feel No need for "maple syrup" thick motoroil.. lol (joking of course) **** in my car i use amsoil 0w30. and it runs great all season and espeically in the winter!!
MolaKule
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Better flow results in better cooling. I proved this to myself on B&S and Kohler engines when running M1 15w50 verses Delvac 1 5W40, Redline 10W30, and Schaeffer's 15W40. The 15W50 increased head temps over the XW40 's and 10W30 synthetics.
Thanks for the info guys. This leads to two other questions:
1. Can the answers be quantified: how much hotter will 20w50 be over 10w40?
2. Are water cooled engines immune from this?
NOTE: I run Mobil 1 supersyn 15w50 (red cap) in my '99 Honda Magna which is a water cooled 750cc V-4. It runs just fine on this oil. Heat is not an issue but I have jetted the carbs (which often makes the engine run a bit cooler).
MolaKule
Staff member
According to my IR thermo, 35 to 75 F hotter.
Water cooled engines should not be immune to the same problems.
[ June 24, 2003, 02:05 PM: Message edited by: MolaKule ]
Water cooled engines should not be immune to the same problems.
[ June 24, 2003, 02:05 PM: Message edited by: MolaKule ]
arkainzeye, I think the reason motorcycle manufacturers specify 40 and 50-weight oils is because they fully expect them to shear down a full grade or more. We've seen that happen in several UOAs and seen it happen fairly quickly.
[ June 25, 2003, 12:51 AM: Message edited by: Jay ]
[ June 25, 2003, 12:51 AM: Message edited by: Jay ]
That doens't make much sense, heck depending on the base stock and the add package it could also thicken up one grade. Then if your running Xw50 you now have a 60wt.
I would say you want to use the thinnest oil, without losing any hydrodynamic lubrication where you have to rely on your barrier additives.
In the case of 20w50 vs 10w40. Most water/oil cooled bikes can use the 10w40 with great results. Most air cooled bikes or V-twins should run 20w50. The reason for the V-twins is becuase the rear cylinder usually runs hotter than the front. So you want to maximize protection.
On my BMW twin it calls for 20w50 in temps over 50 degrees. I ran Amsoil 10w40 year round in El Paso with no wear associated problems. This was with extended drains as well up to 9500 miles.
In the BMW owners Manual they had a chart depicting which oil grades and temps to use. There was a "special oils" section (which I took for meaning synthetic) that allowed the use of Xw40 in temps from 0 degrees to over 100 degrees. So I felt totally confident using this "special" oil as compared to the standard dino BMW oil.
Lastly when talking synthetics compared to conventional you have a higher leaway as far as viscosity goes becuase a synthetic has a natural higher Viscosity Index(VI) which is the relationship to how much the viscosity changes over a range of temperatures.
This mean if you bike or car calls for xw30 you could use xw20 or xw40 with no problems for the same temperature ranges.
To answer your question a thinner oil should cool better because of the increase flow, unless you are so thin that you come out of hydronamtic lubrication where you would see a rapid rise in overall temps becuase of the friction. Also a thinner oil will carry off the heat from bearing journals and cams to the crankcase/oil cooler.
[ June 25, 2003, 08:28 AM: Message edited by: msparks ]
Here is a general use guide I found.
relating to synthetic engine oils only
5W-30
Use in gas engines for best all-weather. Provides quickest starts and fastest oil presure rise.
10W-30
Best all weather grade for vehicles that are driven daily.
10W-40
For engines run in high temperatures, very hot weather on regular basis. Medium and HD truck engine or occasional race use.
20W-50
Ultimate high temp oil, Use for engine that always run high oil temps, have larger clearances, e.g. air cooled or ladge cid. Not reommended for for use in cold climates or for production engines where oil temp is below 225°F.
relating to synthetic engine oils only
5W-30
Use in gas engines for best all-weather. Provides quickest starts and fastest oil presure rise.
10W-30
Best all weather grade for vehicles that are driven daily.
10W-40
For engines run in high temperatures, very hot weather on regular basis. Medium and HD truck engine or occasional race use.
20W-50
Ultimate high temp oil, Use for engine that always run high oil temps, have larger clearances, e.g. air cooled or ladge cid. Not reommended for for use in cold climates or for production engines where oil temp is below 225°F.
An article on oil that I read in a bike magazine years ago stated that the higher viscosity oils themselves generate more heat because of the flow properties. I wonder if this could be proven with some type of mixer running at the same speeds in different weights?
Shearing back: I have an 3k miles analysis of M1 SuperSyn where it fell back to 13.3 cSt @ 100C. Worst case of fallout I've ever seen from this oil, and the analysis didn't find any fuel contamination, either.
Eventually, I'll have UOA's from Delvac 1300 Super, Rotella T Syn, and Texaco Havoline 20W-50 all from the same air-cooled bike. This is going to be interesting. The Delvac did quite well, and the Rot T results should be here in a few days.
KLR650, 10-15 hours of off-roading in hot weather, and some WFO operation on the freeway in 100F heat. I don't have any other UOA results from my KLR. I'm burning up all of my analysis kits on my ZR-7 now.
Oh, and it was API SJ Tri-Syn, not SuperSyn. Error in my previous post.
[ July 05, 2003, 08:47 PM: Message edited by: richard612 ]
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