Straight Weight / Monograde

[jeff78]

Another benefit of monogrades, no VII's to leave deposits:

https://www.bobistheoilguy.com/foru...ich-oils-keep-things-cleaner#Post4918143

Although in a previous post he does say not to worry about that too much.

 

[alarmguy]

Hey Jeff, trying to follow your posts but we are talking and using different numbers.
The link I provided shows viscosity of a straight 30 weight oil thicker at two specific temperatures 50F and 68F degrees then a multi viscosity 5/40 and 10/40.

So I think it would be reasonable to say the same for a 40 weight oil compared to a 20/50 oil and your own posted numbers (that do not show a source) pretty much show its a dead heat between the 20/50 and the straight weight 40 at the same temperatures and the straight 40 is significantly thicker then Mobile 1 15/50.

Anyway, interesting subject for sure and I never thought about running a straight weight in my previous metric bikes with shared sumps, if I had to do it all over again, I would as the multi viscosity oils show no benefit in typical riding conditions of 50/60F degrees and higher. (of course, in that case I would run a straight 40 instead of a 20/50 if I did) maybe, I think to much and no longer have a shared sump.
If I didnt have a LOT of 15/50 oil for my Road King, I very well might have tried a straight 50 which is acceptable even in my Harley Owners manual.

 

[jeff78]

Originally Posted by alarmguy
So I think it would be reasonable to say the same for a 40 weight oil compared to a 20/50 oil and your own posted numbers (that do not show a source)


The viscosities at 40C and 100C are from the data sheets for the oils. The other viscosities were calculated with the viscosity-temperature extrapolation calculator here:

https://wiki.anton-paar.com/en/astm-d341-viscosity-temperature-extrapolation/


Quote
pretty much show its a dead heat between the 20/50 and the straight weight 40 at the same temperatures and the straight 40 is significantly thicker then Mobile 1 15/50.


Yeah, I was surprised to see the 0C viscosity for the M1 15W-50, I wasn't expecting it to be that much lower than those of the 20W-50's.


Quote
If I didnt have a LOT of 15/50 oil for my Road King, I very well might have tried a straight 50 which is acceptable even in my Harley Owners manual.


I'm curious about oil temps on Harleys - do they come with oil temp gauges, or an oil cooler? If you go for a blast on the freeway in 50 degree weather, what does the oil temp look like?

 

[BigCahuna]

I've never been able to get an accurate temp reading of my bikes motor oil,with my point and shoot temp gun due to port where you put the dipstick. But I will say this. A few weeks ago I went out for our weekly Polar Bear ride and the air temp was 28f. For a second there, I didn't think it was gonna start due to it turning over super slow. After 2 tries it finally lit off and wasn't a issue for the 4 or 5 other starts that day. Based solely on using my hand to gauge the motors temp, I'd say it runs alot cooler when the air temps are below 32f. Harley says in their manual to use 10/40 wt oil if the bikes being ridden in temps under 40f, for ease of starting. This was the first time my bikes ever acted sluggish starting in cold weather. My battery is always on a tender when garaged, but the battery is 4 1/2 years old. On a side note, it has a 400cca rating while I believe a battery from Harley only carries a 320 cca. I started it yesterday several time in 40 f temps and there was no problems starting.,,

 

[jeff78]

Originally Posted by BigCahuna
I've never been able to get an accurate temp reading of my bikes motor oil,with my point and shoot temp gun due to port where you put the dipstick. But I will say this. A few weeks ago I went out for our weekly Polar Bear ride and the air temp was 28f. For a second there, I didn't think it was gonna start due to it turning over super slow. After 2 tries it finally lit off and wasn't a issue for the 4 or 5 other starts that day. Based solely on using my hand to gauge the motors temp, I'd say it runs alot cooler when the air temps are below 32f. Harley says in their manual to use 10/40 wt oil if the bikes being ridden in temps under 40f, for ease of starting.


That's interesting - what oil did you have in the bike? 20W-50?

If I had to guess, I'd say the first start was tough because the oil was at ambient temp, and on the subsequent starts the oil was warmed up from the bike being ridden and not given time to cool down too much. The viscosity at, say, 50F will be around half of what it is at freezing, so a little bit warmer goes a long way.

I have a Trailtech oil temp gauge on my bike and I installed the sensor where the main oil gallery plug bolt used to go. The oil passing by has just exited the oil filter after passing through the oil-to-coolant heat exchanger, so it's at the point where oil temps will be lowest. A run on the freeway will have the oil temperature matching coolant temperature - in cold weather this happens fairly quickly.

 

[Silk]

After doing a few day trips, I have just come back from a longer 1,000km ride. Temps were supposed to be around 25c, but in some places there was melting tar, and I could feel the heat off the road...I could only get my temp gun bellow 30c under trees. Sump temps varied from 75 to 90c at various parts of the sump at all times, never going over 90c. This is lower than with 20W-50, as to be expected, but as the sump temps never varied I took it that the oil was doing ok in there. A dipstick thermometer would show higher temps, but it looked ok to me. BMW recommends straight 30 up to 30c.

 

[sunruh]

nice cool temps.

try riding here...were it hits 40-41C

 

[Silk]

Well, that's why I'm trying the 30, because it fits exactly in my temp ran ge.