Minimum oil temperature...? And, where is the oil the hottest?

[Big Dan]

I've seen a good bit of discussion about oil temps, and I'm trying to wrap my head around some stuff. Is there a minimum oil temp (within reason)? I've seen guys say it's gotta be at least 212 to rid itself of moisture, which would seem to make sense. Other guys have said that if the oil reads less than 212 in the pan, don't worry because it's hotter elsewhere and will still rid itself of moisture; this part I'm not sure about. I'm not saying it's not so, I'm saying that I'm not sure about it. This is why I'm asking.

HV sent me a detailed description of the TC oiling system the other day and if I read that correctly, the oil in the pan should be the hottest oil anywhere, yes? No? Maybe? The way I understood it, oil leaves the pump and the pressure is read; then the oil goes to the filter (then through an oil cooler if one is installed), then it goes back to the cam plate, and on to the top and bottom ends. I assume that from those points, it collects in the sump, is scavenged, and goes back to the pan.

So in my head, the oil has been through the filter (and the cooler if there is one), then it's gone through the engine and picked up all the heat that it's ever going to, and then finally back to the pan where the temp is read. Can an oil cooler be too efficient?

Here's a hypothetical situation. The thermostat begins to open at 180, and is supposed to be fully open at 210. What if, once it reaches 180, it won't climb any further? Is the oil cooler pulling too much heat out of the oil? Is that even possible?

[rbabos]

180 is the min for removing moisture from my experience with other engines. 210 ish is usually the optimum temp to reduce drag and flow well. I'd think the oil in the heads is the hottest but not there long since it travels back to the pan. It would  seem the temp in the pan is the most valuable reading since this is what the pump gets to feed the rest of the engine.
With a thermostat controlled cooler and the temp dropping to less than 180 it's most likely cooling from cold air hitting the engine, or as your example not going over 180 to keep the t stat open. Depends on ambient temps.
I run a vertical Jagg with no stat and in cooler weather it needs to be covered up. Even then it's hard pressed to hit 180 on cooler days on a long run. I did remove the cooler once to compare between taped and no cooler and the temps were about the same.
Ron

[fourthgear]

Not sure how your thermostat is routed ,but on most its a bypass valve , where it bypasses the oil cooler ,than as temp. warms past set point of thermostat ,it would go through the cooler as needed or until it warmed up enough to have the valve open all the way to full cooler route & no bypass.
I would also say the heads may be the hotest point or some where in between them & oil bag.(pan )
I just rode into work today & it was about 65 deg. out ,a 20 mile ride to work @ 70-75 mph & my oil temp on the gage never got past 170 deg. & I do not have a cooler .

[Big Dan]

Thanks, Ron

Thanks to you too, fourthgear.

The thermostat is pretty much the standard deal. The oil gets filtered hot, then either goes back to the engine or is diverted to the cooler, depending on oil temp. The 'stat begins to open at 180, and is supposed to be fully open at 210.

In this scenario, the bike was on the lift with a fan blowing sideways across the engine. Ambient temperature was about 40 degrees with the doors open, but there was no air flow on the oil cooler at all. This particular cooler is designed to give up most of its heat by radiation as opposed to convection, but I was surprised that the oil temp went to 180 and wouldn't go up any further at all with no air flow across the cooler whatsoever.

We're a couple of months away from riding weather of any kind, and won't see any hot weather for at least 4 months, so I'm limited in how I can check things further (at least in real-world conditions). I suppose I should cut a hole in a wall somewhere and add an exhaust hose so I can run the bike with the doors closed and heat it up a good deal more in the workspace. Maybe wrap a blanket around the cooler and let the oil get good and warm, then pull the blanket and see how long it takes the oil to cool down.

Any other thoughts or suggestions?

[chopper]

The oil is hottest on the valve stems and especially where the jets spray onto the bottom of the pistons and cyl walls.  Thats where dyno oil starts to fail first.  It may read say 220 in the tank but it will be MUCH higher in those areas, and consequently scorch.

  As far as condensation coming out of the oil? It will burn off at a MUCH lower temp than 180. It'll even come out at 120, it will just take longer. Don't believe that? Take some moisture laden oil, put it in a pan on the stove, and measure the temp as you warm it slowly.. (I've actually DONE it, to satisfy myself)

   Also consider this. I have a little Ranger pick up. It was minus 8 this morning. Now.. if I drive it to town, about 6 miles, the thermostat won't open for 3-4 miles. Consider that the oil pan hangs down in the breeze. I can rive to town, shut it off, and lay my hand on the oil pan. It is BARELY warm... (done that also) yet never any condensation build up.

[Big Dan]

Chopper, that all seems to make sense, but it's also where I get lost. The oil has already been through the filter and the cooler, and then hits the valve stems and the piston jets, and then finally back to the pan. It makes sense in my head that those would be the hottet areas, but I'm having trouble getting my head around how it could cool off between those areas and the pan.

Wait... I think it just hit me. Not all of the oil hits those "hot" areas in a single pass through the system. The small portion of oil that hits those "hot" areas then mixes with the much larger portion of oil that hasn't been to those "hot" areas in a single pass, and then it all goes back to the pan; thus the "lower" reading at the pan.

As far as the temp that the moisture goes away, I have no position... that's why I'm asking. And I'm not about to cook a pan of motor oil in Da Bride's kitchen. I'd like to live at least a little while longer.

[iclick]

There is no magic number for a minimum temperature to remove moisture, as it will simply dissipate faster as temperature rises.  Even at ambient temperatures water will evaporate, and if you heat it to 150° it will do so faster, and faster yet at the boiling point.  I don't know where people get the idea oil needs to be 212° before any water can dissipate, as this just isn't the case.

[Big Dan]

  Well said, iclick. Thanks.

[Ed Y]

Some more food for thought. I've got a 2002 RG with an oil temp gauge and the sensor mounted in the oil tank next to the drain. It's very interesting to watch the temp gauge while traveling especially during the summer. The gauge can read 210-215 with temps in the 90's. If you run up on some wet pavement with small patches of water still standing, the temp gauge will drop drastically, almost all the way down. I've also seen this when outside temp is 40 and you hit a wet spot.

I guess the point I'm trying to make is that temps as reported by other riders depend on many variables. Measuring it in the oil pan is definitely (IMO) not the best place cause it can be too easily influenced by outside environment. The best measurement for everyday use would seem to be right as the oil comes out of the cam chest heading for the oil pan. HD tried the sensor there but that location wasn't used very long. Even there water on the road would get to it somewhat. Actually, if the sensor were built into the cam chest might be the best place. Just a thought.

[Big Dan]

Ed,
Mine will drop like that if I hit a wet spot also. I've always figured it was due to evaporative cooling at the bottom of the pan, which as you say, is right where the sender is. I guess a guy could try to tap in right where the pressure sender is with some creative plumbing, but if I read the stuff right that HV sent me that would basically be the same as the pan anyways, as far as temp goes.

[bigfoot5x]

I agree that water will evaporate from oil at less than 212 degrees. After all, for years the normal thermostat for car engines was 180 to 190. The norm now is around 200 or slightly above. I think that has more to do with emissions need than water evaporation. Inboard boat engines use a 160 degree thermostat and they are definitely in a moist environment. I should say that my boat engines all came from the factory with 160 degree thermostats. Their shop manuals do state the the thermostat really needs to work to that temp so the water will evaporate. They have a tendency to stick in the open position and then the engine never really warms up. I have not bought a newer boat with EFI so I don't know what they are using.

[rbabos]

I agree moisture will leave the oil at lower than 180, but the problem is at around 150 the engine is condsensing at a rate higher than what the evaporoation is. A good indicator of this is if you have external breathers to the ground. If you see water dripping, the oil is taking on water. Getting the temp to at least 180 for a long ride the condensation stops and you start winning with moisture removal. At 150 it's a losing battle and frequent oil changes are the only solution. Spring and fall , lot's of condensation going on, especially shorter rides.
Ron

[FXDBI]

I agree moisture will leave the oil at lower than 180, but the problem is at around 150 the engine is condsensing at a rate higher than what the evaporoation is. A good indicator of this is if you have external breathers to the ground. If you see water dripping, the oil is taking on water. Getting the temp to at least 180 for a long ride the condensation stops and you start winning with moisture removal. At 150 it's a losing battle and frequent oil changes are the only solution. Spring and fall , lot's of condensation going on, especially shorter rides.
Ron

I think it will vary with the humidity in the air, its very dry here and I have never seen any moisture out of my breather hoses to the ground. Also never run the bike under a 1/2 hr when its up for its first run of the day. Years ago the old guy I did my automotive engine training under told us it takes 20 Min's for a engine to warm up and remove any HARMFUL moisture out, always kept that has a rule of thumb. Oil off the piston jets is probilly the hotest oil in the bike.....Bob

[rbabos]

I agree moisture will leave the oil at lower than 180, but the problem is at around 150 the engine is condsensing at a rate higher than what the evaporoation is. A good indicator of this is if you have external breathers to the ground. If you see water dripping, the oil is taking on water. Getting the temp to at least 180 for a long ride the condensation stops and you start winning with moisture removal. At 150 it's a losing battle and frequent oil changes are the only solution. Spring and fall , lot's of condensation going on, especially shorter rides.
Ron

I think it will vary with the humidity in the air, its very dry here and I have never seen any moisture out of my breather hoses to the ground. Also never run the bike under a 1/2 hr when its up for its first run of the day. Years ago the old guy I did my automotive engine training under told us it takes 20 Min's for a engine to warm up and remove any HARMFUL moisture out, always kept that has a rule of thumb. Oil off the piston jets is probilly the hotest oil in the bike.....Bob

Agree 100% on the humidity thing. I've seen cold dry days where the breather don't sweat. Unfortanately in southern Ontario humidity is usually up there most of the year.
Ron

[HDDOC]

I had a talk with a Jegg Oil Cooler Rep. He claims that the HD premium cooler filter adaptor sends the hot oil to the cooler first and then filters the cooler oil. Claims his adaptor sends hot oil thru the filter then to the cooler which is a better design.    Doc

[Big Dan]

Filter-first is said to be better, so that you're filtering the oil while it's hot and more free flowing. Mine definitely filters first, and I thought they were all like that. I could easily be mistaken about that though. Anybody know for sure?

[HDDOC]

I received this info direct from Jagg, you may want to call them to verify.  Doc

[Big Dan]

Doc,
I don't doubt for a minute that that's what the Jagg guy told you. I hope it didn't come across like I did. I just found it a bit surprising as I had assumed that they all work like the Jagg unit works. Luckily, mine does, and that's the only one I'm really concerned about.

[iclick]

I agree moisture will leave the oil at lower than 180, but the problem is at around 150 the engine is condsensing at a rate higher than what the evaporoation is. A good indicator of this is if you have external breathers to the ground. If you see water dripping, the oil is taking on water. Getting the temp to at least 180 for a long ride the condensation stops and you start winning with moisture removal. At 150 it's a losing battle and frequent oil changes are the only solution. Spring and fall , lot's of condensation going on, especially shorter rides.

I do work for Exxon-Mobil and have talked with Mobil 1 engineers about some of these topics.  My concern has always been "crankcase dilution," described in my 1966 Corvette service manual as water (a byproduct of combustion) and resulting sulfuric-acid creation.  Acid can cause pitting of cylinders, rotting exhaust systems, and other problems--so getting the water out is important.  Because of this I've always tried to make sure my vehicles are fully warmed-up before shutting them down by linking short trips into longer ones, etc., at least when possible.  The engineers I've talked to say this isn't as much of a concern as it was in years past because there is less sulfur in gas and oil additives can handle acid and water much better than before. 

My old Evo never did heat the oil up very high even without an oil cooler, and it would normally stay <160° except occasionally in hot summer traffic where it would sometimes hit 180°, 200° being the highest I ever observed.  I've always used 5k drain intervals and sent two used-oil samples, one in summer and one in winter, to a lab for analysis.  The TBN (Total Base Number, which reflects the oils ability to absorb acids) was well-within safe limits even after 5k under the relatively cool conditions of the winter sample.  Their estimate was that it would last 8k in the winter sample and 10k in the summer under those conditions.  My TC96 runs much hotter, typically 200° while moving in 90° weather, never higher than 230°--so I don't worry too much about the oil being able to handle the contaminants, as I'm using the same brand.  OTOH it can climb no higher than 150° in cool conditions like we're having now in S. LA.  On a long ride recently my front head temp stayed <200° and I never saw oil (measured in the pan) higher than about 150°.  I'm running an HD Premium cooler with a thermostat that opens around 180-185° based on the oil-temp gauge.

[HDDOC]

Doc,
I don't doubt for a minute that that's what the Jagg guy told you. I hope it didn't come across like I did. I just found it a bit surprising as I had assumed that they all work like the Jagg unit works. Luckily, mine does, and that's the only one I'm really concerned about.

I was also surprized at what the Jagg rep. told me and had to ask him twice if is info was correct. He further explained to me he had at the time both adaptors if front of him and was sure of the flow. I wish there was and easy way to prove it myself.   Thanks Doc

[rbabos]

Doc,
I don't doubt for a minute that that's what the Jagg guy told you. I hope it didn't come across like I did. I just found it a bit surprising as I had assumed that they all work like the Jagg unit works. Luckily, mine does, and that's the only one I'm really concerned about.

I was also surprized at what the Jagg rep. told me and had to ask him twice if is info was correct. He further explained to me he had at the time both adaptors if front of him and was sure of the flow. I wish there was and easy way to prove it myself.   Thanks Doc

Don't know about the HD adapter but the Jagg definately filters first, then cools. I check it out prior to install.
Ron

[chadlyp]

i'd like to point out that per HD, "Normal Operating Oil Temp" is 230degreesF... the reason for that oil temp (measured at the dipstick) is that if the oil in the pan (tank on Softail) is at 230, then the engine parts are at the intended temps during normal operating conditions... what's important about that, is that before those normal temps are reached, the pistons are not round and straight, the bearings & bushings are running excessive clearances, and all other moving parts are also running excessive clearances... every piece and every clearance is engineered by some pretty intelligent individuals and 108 years of experience... the same goes for the factory "lack of" oil coolers in the first place... if it needed it, you wouldn't be having to add it on... it's an air cooled motor, it's supposed to run hot... believe me, or if not then believe the engineers who designed it, IT CAN TAKE IT!, and the motor doesn't even run at max efficiency with minimal wear unless it is hot! every now and again i'll get a guy that wants an oil cooler because he rides in slow runs, traffic, and/or parades a lot and isn't moving fast enough for the moving air to properly air cool the engine... guess what an oil cooler needs in order to be effective... that's right, fast moving air! that argument is now null and void... some say they are doing it for increased oil capacity... really? again, remember, very smart engineers came up with those capacities, but even if you just like extra oil, and extra-long oil filter will give you extra capacity too AND it only costs $14.99

[chopper]

believe me, or if not then believe the engineers who designed it, IT CAN TAKE IT!,

Uh huh...  and these are the same "engineers?" who gave us a lousy cam chain tensioner set up, got rid of the Timken crank bearings in 03, the infamous flexible crankshafts, and horrendous crank runout..

Some facts..
  HD is the ONLY manufacturer to use piston oil jets to cool their pistons, that does NOT have a cooler on their bike. here do you think all that extra heat goes?

  Oil coolers work quite well at a dead stop. Not as well as rolling, but still quite effective. Doubt that? Get an infrared thermometer and measure the damn temps yourself!

  230 degrees on fossil oil definitely starts to degrade. And as I've said before, if you tank temp is 230, the oil temp on the bottom of the pistons (and cyl walls) is WAAAY higher. Consequently the oil as it hits those surfaces is super hot, and BURNT.

BTW...those "engineers?" of which you speak so highly of, are the same ones that told us NOT to use synthetic oil....EVER...    then brought out rebranded Citgo synth, and said "Hey, it pretty damn great stuff!"            now that WE sell it"

[Admiral Akbar]

Also when HD design the engine. production was delayed while they looked at ways to cool the motor down.. During design oil temps on pre-production engines was in the 270s..  It wasn't until the found that they were pushing too much oil through the heads that where able to get the temps down to 230.    The ""Normal Operating Oil Temp" is 230degreesF" is more if a statement that it's OK for the temps to be up to 230 instead of it needs to be 230..  The important thing is to not run Dino too much above that.   

Max

[05FLHTC]

Dan, IMO & this is only an opinion not backed by anything scientific anything up to near 170ish should suffice.