I bought a oil dipstick temp gauge. After a weekend of riding my results so far.
Did a poker run Saturday with runs fifty miles between stops. The temps were running 223 degrees riding two up. At 90 degree ambient temp.

On Sunday the longest non stop run was a hundred miles in 90 degree ambient temp. The oil temp was 233 when I got home. I was riding down the hwy at 75 to 80 mph.

I don't have any long runs coming up in the near future. So this report is pretty limited. I'm still a little surprised at the temps. The oil is cooler than an old soft tail I used to run years ago. There's not much chance on traffic jams where I live. (thank god I got out of all that mess) I need a vacation, so I can see whats really going on.

This is on a oil cooled FLRTXS.

 

It's a partially liquid cooled motor. It only make sense the oil temps would be lower then an air cooled motor.

 

A vendor is reporting that in 60 degree temps the oil returning to the pan from the heads is 265+ degrees. I guess that is the oil returning, not the actual pan temps after.
And of course that is making people go crazy since everyone is an internet engineer...

Thank you for your observation. So 90 degrees ambient and seeing 233... That's more in line with others are seeing here locally.
I have yet to stick a thermometer into my Twin-Cooled to see what's what but will sometime this week.

 

My twin cam 107 ran normally around 220- 230 in 90 degree temp get in slow stop and go traffic it would push 280-290. Never a problem ran 20-50 syn

 

I reported the oil temps from the heads as well as pan (sump) temperatures. Sump temperature ran around 250 - 260 on the high side and around 230 at freeway speeds. The return oil from the heads at high temperatures is what can break the oil down and once that happens the oil needs to be changed or engine damage can and will follow. The problem is going to come more from bikes running in higher ambient conditions and slow moving conditions. Those conditions just happen to be the normal riding conditions here in So. CA and much of the South Western US.

 

I know the main topic is oil cooled bikes, but I wanted to add a little something just for reference.

On my twin-cooled 17:
This afternoon at 88 degrees, sump temp was 230 on the HWY 70-80 MPH, 245 in stop and go traffic right after. That's 7 miles of stop and go and it only reached 245. Pretty nice.

 

The weather has warmed back up to the same as the first round of testing. Now the bike is equipped with full instrumentation and recording of the ECM data along with the Front Cylinder Head temperature, Rear Cylinder Head temperature, Oil Sump temperature and Head Oil Return temperature. I saw slightly less Measured Engine temperature on this ride than I did in the first testing, 351 F the first time and 340 F this time. The ride was in-town running posted speed limits with light to no traffic, for about 18 miles.

Conditions:
Ambient temperature during testing upper 70's
In Town riding with little traffic but normal stop lights
Speed limited to posted speed limits (35 - 45 mph)

Results:
Measured Peak Engine temperature = 340 F
Measured Peak Oil Sump temperature = 267 F
Measured Peak Head Oil Return temperature = 290 F

So for me, its change the oil to full synthetic and wait for the fan assisted oil cooler to come off back order. Once the new oil cooler arrives I will install and test again.

 

So why is this so important to know what temp your oil is?


Oil breaks down duh. You can change the oil when it gets dirty, another duh. The whole point of oil is to lubricate the engine and prevent it from not destroying itself.

Do you want to run cooler temps for longer service intervals? You still have to change the oil anyways every 5K, so why does it even matter? Oil is suppose to break down, do you not want it to breakdown?

Luckily my bike consumes oil down to the last 3 ticks of the oil dipstick when it is time to change the oil.

 

The reason you want to know is because oil breaks down due to HEAT. So you can take brand new oil and ruin it by running it to hot in as little as 50 miles. So now it does not lubricate the engine components and you then ruin the engine. So is that OK with you? Regular oil like HD puts into the bikes is not any good above 280 deg F for very long, synthetic oil on the other had will go to 330 F without issue. Most regular oil manufactures will tell you to run oil between 180 - 250 F for normal operation range so 290 is a bad deal and is breaking the oil down.

 

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Jut to add a few things i have noticed on the air cooled v-twins i have owned & ridden over that past 46+ yrs riding on the street & wrenching bike/car motors is when oil temp hits approx 220-230deg f things that to change like more valve/lifter noise along with considerably lower oil pressure.

My TC 96" mostly stock used to run approx oil temp in 90+ deg f summer heat of 6-8psi @ idle & 32psi @ cruise resulting in increased valve & lifter noise,detonation at times along with much more negative performance & rider comfort issues too.

But post installing an ultracool oil cooler with twin cooling fans & wards cooling fans oil temp was reduced 50deg f hot oil pressure in summer heat improved from 6-8psi @ idle & 32psi @ cruise WITHOUT COOLING to now 18psi @ idle & 45-47psi @ cruise in same summer heat along with valve train being totally quiet and no more detonation too.

Oil temp prior to installing the 2 cooling mods used to run approx 230 @ cruise,250+ deg f in moderate traffic and approx 270-280 deg f in heavier traffic in summer heat.

Post installing the 2 cooling mods oil temp in my bike nor run approx 185-190deg f @ cruise ,215-220deg f in moderat traffic & 225-230deg f max in heavy traffic in 90deg summer heat.

Now with the 2 cooling mods & spectro oil in more extreme 98-100+ deg f summer heat oil temp @ cruise still runs 190ish deg range but after enough miles & time will slowly increase to 215-220deg f where the twin elec cooling fans kick on.

Then with cooling fans on the oil temp will either returns to 190-195ish deg f where they turn off again or in worst case the cooling fans remain on for a longer period of time keeping oil temp from going over 225-230deg max @ cruise in 100+ deg heat and eventually reduce oil temp 190-195deg f after being on for a long time vs without cooling oil temp hitting 250+ deg f @ cruise in same cond.

And in moderate avg everyday traffic hitting 3-4 stoplights in a row then up to 45-50mph for a couple miles then back 2 stoplights again in 98-100+ deg f summer heat with the 2 cooling mods maxes out @ approx 230-240deg f even sitting still in traffic vs oil temp hitting 275-280deg f without the 2 cooling mods in avg traffic cond and pushing 290-300ish deg f in heavy traffic.

And again,thats also with running spectro 20w-50 motorcycle oil specifically formulated for lrg disp HD v-twins that i found from testing in my bike faired better then HD syn3 syn and a few other popular 20-50 motorcycle oils were in my bike when it came to reducing valve train noise & maintaining better/higher oil pressure in summer heat.

Scott