Normal OIL Operating Temperature Is:_________?

[captmako]

Just did some carb. tweaking and putting new fuel lines on my '86 Naked R80. Started her up and did a quick
warm-up at idle. Just for the heck of it - checked oil temp. and was at 80 degrees C. which is approx. 176 degrees F.
What is the normal RUNNING temp. for an airhead? I did a search and didn't see anything of note. I think I read
normal RUNNING temp. was around 200 degrees F. to maybe 220 degrees F.??????????????????????????? Sound right?

[PITAPan]

Just did some carb. tweaking and putting new fuel lines on my '86 Naked R80. Started her up and did a quick
warm-up at idle. Just for the heck of it - checked oil temp. and was at 80 degrees C. which is approx. 176 degrees F.
What is the normal RUNNING temp. for an airhead? I did a search and didn't see anything of note. I think I read
normal RUNNING temp. was around 200 degrees F. to maybe 220 degrees F.??????????????????????????? Sound right?

Temp of what? The two that matter are oil temps and head temps.

At sea level you want your oil temps at 212F minimum. This isn't an airhead thing, any engine. Minimizes water mixing in the oil. Go higher and you shorten oil life. Check the bob is the oil guy site for data on that. 220F for running temp is nice. it will go a lot higher at low speed running (thick traffic) or with very heavy loads (including abnormal loading, like a brake or clutch problem). Mine goes well over 320F coming off the head in heavy slow traffic on a warm day.

I measure oil temps coming off the head at the push rod tube and in the back of the sump. But I also have a lot of cooling gear and a hot running engine. The oil off the head tends to lead and it takes a long time to equalize with sump temp---but I'm still gathering data and don't have a really clear picture yet.

Your tuning has a big effect (next to outside temp and riding conditions). Exhaust and head temps are the most sensitive and give you a picture of what is happening on each side---mostly of your mixture. But you can get a similar picture looking at the plugs, which also indicate cylinder temp. confounded with the cooling characteristics of the plugs themselves.

[barryh]

It's an air cooled engine so what's normal will depend to some extent on the local climate. I'd be ecstatic if I could get my oil as high as 80 C in the middle of a UK winter. I'd say 80 C is hot enough to tune the idle mixture on the carbs if that's what you were thinking about. I don't get 100C even in the summer. I'm talking sump measurements at the end of I ride so I know it's going to have be higher in some parts of the engine. 100 C is a good target though.

[R100RTMark]

I have a VDO sump plug/gauge setup on my 1994 R100RT. This from memory, but it will be about right. In moderate ambient and if I keep moving (at pretty much any speed) recorded oil temperature typically hovers just above 180F (82C) which, I know by testing, is the temperature that the thermostatic valve in the oil cooler line starts to open. In low ambient, say anything less than 45F (7C) it might not even get to 160F (71C). In higher ambient, say 90F (32C) or putting a little more load on the bike and running up and down the gears, say camping gear and North Georgia Mountain twisties, then 200 to 210F (93 to 99C) would not be unusual. By far the most onerous conditions for the bike, regardless of ambient but particularly above 90F (32C) , is stop/start low speed traffic. Easy to see the oil temperature rise to 220F (104C) or a little higher, and do so quickly if ambient is high.

[Roy Gavin]

If you have an oil question you should really as it over on the Bobistheoilguy forum.

The guys over there are industry pros , and without intending any disrespect to any posters on this or any other forum, are qualified to answer the question and are abreast with current developments.

But FWIW on a multigrade oil the high rating is taken at 90c so that might tell some people something. Like if you need 50 wt dont run the oil any hotter than 90c or it will be thinner.
And the rate of oxidation of the oil also increases greatly for a modest increase in temperature - if some oils are run much over 120C they will be as black as treacle in 600 km

Also , a major part of oils work is to cool the high stress areas, and of course the hotter it gets the less cooling it does, so the ability to evaporate a bit condensation might not be the sole consideration.
But you will have more flow with hot thin oil so this might be self regulating to a certain extent.

And also it is relevant that oil does not flow like water, as there is much more viscosity change with temperature.
So cool oil sticks to a cool surface and only the hot circulates - late in the day BMW realised this and started to put the fins on the inside of the sump instead of the outside.
But you still want the oil hot enough that all of it circulates, so cold is no good either.
This is particularly noticeable with the Rotax, which is semi wet sump with oil in the sump and in a header tank.
There is no thermostat anywhere in the oil system, but on a cold start the oil is puled down into the motor and stays there until the motor is good and hot.

Also a good Ester synthetic keeps in shape better than a Dino , and will probably perform OK 15/ 20 c hotter.

As far as maximum power from a probably wide tolerance/ high flow race motor go the hottest the oil will take is the best for power, and oxidated oil can be changed between races, but this does not necessarily apply as a sensible approach for a street motor.

So, no easy answer, but it would seem from the previous post ,which is pretty much what I find myself, that somewhere between 180 / 220F is norm on most airheads, and this keeps the temp below the Red danger zone on most gauges.

[PITAPan]

If you have an oil question you should really as it over on the Bobistheoilguy forum.

Some salad dressing for that? Agreed, that can be a good forum.

The guys over there are industry pros , and without intending any disrespect to any posters on this or any other forum, are qualified to answer the question and are abreast with current developments.

But FWIW on a multigrade oil the high rating is taken at 90c so that might tell some people something. Like if you need 50 wt dont run the oil any hotter than 90c or it will be thinner.
And the rate of oxidation of the oil also increases greatly for a modest increase in temperature - if some oils are run much over 120C they will be as black as treacle in 600 km

Treacle!!?? Oh my. Terribly dramatic. Uh...which oil is this again? The stuff in my fry pot is pretty thick and I only did one batch of fritters. So not that one I guess. I think it was soybean. But your drama so you gotta say what this death oil is. Exactly. (saying it's what ME109 uses won't cut it and it's been done anyway).

I was on a clockmakers supply site the other day. Boy do they have a lot of interesting oils for clocks and watches---some of them as antique as the mechanisms they are matched to. interesting stuff.

Also , a major part of oils work is to cool the high stress areas, and of course the hotter it gets the less cooling it does, so the ability to evaporate a bit condensation might not be the sole consideration.
But you will have more flow with hot thin oil so this might be self regulating to a certain extent.

Stress is the application of force. Just sayin' . You got lead astray by something Bob got wrong. see below. On an oil cooled motor part of the oils job is cooling but I'll argue the major part of what it does is lubrication. But airheads aren't oil cooled motors. The oil is doing everything it can to keep itself cooled.

And also it is relevant that oil does not flow like water, as there is much more viscosity change with temperature.

mmm...ya left out a piece---the transmissivity of heat through the oil. If you have some oil at some temperature so that the viscosity is the same as water, it flows like water. if you have some treaclel at some temperature so the viscosity is the same as oil it flows like oil.

So cool oil sticks to a cool surface and only the hot circulates -

This assumes you have a temperature gradient through the flow between the walls of the tube containing the oil flow and the center of the flow. But we aren't talking arctic pipelines, we are talking oil passages a few millimeter across. The effect doesn't scale down (largely due to turbulence effects on that temperature gradient), especially when the walls are hot and the oil cold.

late in the day BMW realised this and started to put the fins on the inside of the sump instead of the outside.

Well...No. The rate of heat transmission through something like an oil pan involves effects at two boundaries. At each one the temperature differential, fluid heat transmissivity (including turbulence) and the surface area are the most important. So you have hot oil to aluminum on the inside, then aluminum to air on the outside. Of the three variables, transmissivity in the fluids (oil and air) and through the aluminum, as well as transmission at the boundaries--oil to metal then metal to air then the surface area available to the boundaries, two are fixed, can be assigned constants and disregarded further. The only thing to work with to get the best cooling is the surface areas. If the surface area on the outside can radiate more heat than the surface on the inside can pick up you lose efficiency. So you increase the surface area on the inside to match what the outside is capable of. You put fins on the inside.

The absolute ability of a fluid to carry heat is only related to it's heat capacity, not it's temperature---up to it's transition temperature. In phase change it's a different set of rules. The ability of the fluid to dissipate heat somewhere is a function of the heat differential across the boundary and the characteristics of the boundary itself---things like fins and surface textures and the nature of the materials (stainless vs aluminum for example).

If the oil has a lower viscosity, because it's hot or for any other reason, you can get more turbulance on a surface and thus more exposure of a given unit of fluid per unit time to the boundary.

A cold viscous fluid flowing (or being stirred) under pressure will heat itself up from internal friction. So in your pipeline where heated oil is being pumped through a cold pipe, the interface between the cold oil at the pipe wall and the hotter internal flow is a point of friction and some of the energy in the flowing oil actually ends up heating up the cold stuff along the walls. if you have doubts and a good thermometer, throw some oil in the blender you don't care about, spin it up and watch it heat up.

But you still want the oil hot enough that all of it circulates, so cold is no good either.
This is particularly noticeable with the Rotax, which is semi wet sump with oil in the sump and in a header tank.
There is no thermostat anywhere in the oil system, but on a cold start the oil is puled down into the motor and stays there until the motor is good and hot.

The airhead is not a Rotax. All the oil is in a big puddle at the bottom. The pump draws cool (?) oil off the bottom of the puddle and the zero pressure hot (?) oil is dripped back onto the top of the puddle. It is not a wet sump insomuch as the crank isn't splashing about in the oil puddle (post '70) so all circulation in that puddle is from the action of the circular flow (literally dripping back on top) and the sloshing from vibrations and movement of the bike on the road.

looking at temperature in the oil the stuff gets quite cool before it gets back to the sump---or rather, the hot spot (oil running of the exhaust side of the head) and the cool spot (bottom of a Briel cooled sump---I think) has a pretty good temp spread for some time after setting off. How much and how long? Still collecting data. But I am very interested in just how that puddle heats up and am investigating it.

Also a good Ester synthetic keeps in shape better than a Dino , and will probably perform OK 15/ 20 c hotter.

The classic argument against synthetic is that it leaks past the old seals in our old airhead engines. perhaps this has improved--but I don't see the "high mileage" oils (lot o anti-leaks stuff in those) in synthetics. But I'll add two more arguments: marketing problems. The mfgrs. want to sell oil. They don't care about your engine. Only with selling oil. The old engine technologies that demand certain types of additives are a small market. Special oils are made for those markets but the thrust for the synthetics seems to be the big markets---new cars. Perhaps there is a syn. packed for flat tappet engines. Dunno. Haven't spotted it. As you noticed on the Bobistheoilguy site, there is much mention not of the oil wearing out, but the additives wearing out. So maybe your base snythetic is pretty durable, the modern additives are the same. But even with a more durable base, as you point out, you can't take advantage of it. The oil filtering setup has some weak points, like the filter bypass. You really need frequent changes to keep the oil clean. So you can't take advantage of the longer lived stuff. Your oil change intervals don't change. On top of that the prices are silly. You can have fresh oil more often with ordinary (correct additive package) dino. I can add my own goodies (Lubromoly moly additive) to Castrol 4T and still have less cost than Castrol Syntec. Hello?

You do have to watch out for the not so fine print on the Bobistheoilguy site. He is very specifically taking about water cooled automotive engines. This is not what we got and a lot of the information does not apply. he doesn't even go back far enough to discuss the relative properties of an SG oil, not are his pressure/rpm measurements applicable to the airhead (I measured). it's a different deal---so be careful. he is also no mechanic---betrayed by his facile comment to just change the gaskets if they are leaking on an old engine. Maybe the guy who maintains his Ferrari does that for him and he never sees the bills (I know people like this). his comment on oil running off parts betrays some things he don't know.

As far as maximum power from a probably wide tolerance/ high flow race motor go the hottest the oil will take is the best for power, and oxidated oil can be changed between races, but this does not necessarily apply as a sensible approach for a street motor.

You actually change the oil pump in the race motor. See the current thread on that old racer for sale. The sale literature has nfo on the changes in the oiling system.

So, no easy answer, but it would seem from the previous post ,which is pretty much what I find myself, that somewhere between 180 / 220F is norm on most airheads, and this keeps the temp below the Red danger zone on most gauges.

[/quote][/quote]

Actually there is an easy answer. Will your oven hold a steady measured 180F? Got that old blender you used before with some oil? Wanna know the difference between running at 180 and 212?

[barryh]

Bit of useless information.

Oil never quite gets thin enough to flow like water.

Viscosity of water at 20 C = 1 cP

Viscosity of 20W50 at 150 C = minimum of 3.7 cP I gave up trying to calculate when it gets down to 1 cP as it would never get there.

In case you are wondering why I used cP it's because it accounts for differences in density.
Centipoise = Centistoke x Density

[Major Softie]

Stress is the application of force. Just sayin' . You got lead astray by something Bob got wrong. see below. On an oil cooled motor part of the oils job is cooling but I'll argue the major part of what it does is lubrication. But airheads aren't oil cooled motors. The oil is doing everything it can to keep itself cooled.

1. You really have to stop restricting yourself to a glossary of mechanical physics in your criticisms of terminology. Words often have more than one meaning in our language, and this is one of those cases. The narrow little definitions of most technical fields are in conflict with the dictionary definitions once one leaves the classroom. There was absolutely nothing wrong with his use of the word "stress," even if it doesn't belong on a Physics exam.

2. You are entirely wrong in your statements about cooling. While oil's primary job is lubrication in all engines, oil is also a vital cooling agent in ALL air-cooled engine. The only difference between an "oil-cooled" and an "air-cooled" engine in this regard is that an "oil-cooled" has some additional passages designed only for cooling certain areas (such as around the exhaust valves on BMW Oilheads), but both designs have the heat transfer abilities of oil as important consideration in the design of the engine.

Treacle!!?? Oh my. Terribly dramatic. Uh...which oil is this again? The stuff in my fry pot is pretty thick and I only did one batch of fritters. So not that one I guess. I think it was soybean. But your drama so you gotta say what this death oil is. Exactly. (saying it's what ME109 uses won't cut it and it's been done anyway).

Dickish. Really dickish.

[PITAPan]

Bit of useless information.

Oil never quite gets thin enough to flow like water.

Viscosity of water at 20 C = 1 cP

Viscosity of 20W50 at 150 C = minimum of 3.7 cP I gave up trying to calculate when it gets down to 1 cP as it would never get there.

In case you are wondering why I used cP it's because it accounts for differences in density.
Centipoise = Centistoke x Density

Interesting. What equations are you using? I'm bad at math but have some formidable tools.

[barryh]

Interesting. What equations are you using? I'm bad at math but have some formidable tools.

I tried first using this calculator http://widman.biz/English/Calculators/Operational.html which wasn't getting any where close to 1 then it occurred to me that the HTHS viscosity spec. pretty much answers the question. SAE J300 standard for HTHS says 20W50 must be a minimum of 3.7 cP at 150 Deg C. I didn't think it worth considering higher temperatures.

HTHS viscosity (High Temperature High Shear) is an important spec for oil but gets rarely mentioned. It's what counts before ZDDP comes into play.