Talk Morgan Forums Morgan Sports Cars Morgan Three Wheeler & Super 3 oil cooler installation

Which is the critical oil temperature to risk any damage to oil quality or motor function?

My wife's heritage runs 230-240f {my road king about 10+ less). I use Mobil one v-twin 20-50w. I would be willing to bet it is mostly the temp at the jugs that makes oil break down, hence the need for the "urban fan".

From machinerylubercation.com


Before selecting a high-temperature lubricant, you must first know when a temperature is considered to be high. Unfortunately, there is no single right answer to this question. For the sake of reference, generally an oil that is able to work at temperatures higher than 210-250 degrees F (100-120 degrees C) for a normal or extended drain interval may be assumed to be a high-temperature lubricant. Of course, other sources may have different opinions on this temperature range.

according to Mobil about their v-twin oil (I am assuming they mean the temperature at the heads, not the tank)

"Mobil 1 advanced synthetic motor oil provides outstanding high-temperature performance and is proven to protect at engine temperatures up to 500°F."

When asking this question, you also need to ask what is the critical low temperature for the oil. Oil must get hot enough to evaporate off the assorted nasty volatiles that get in it from the combustion process and the water that inevitably gets in from the same source and from condensation when left to stand. These nasties are really bad for engines.
In a hot climate with lots of low speed running there may be good reason for oil cooling but as the engine is air not oil cooled, you may find that in those conditions the oil reaches similar instantaneous temperatures at the various hot spots in the engine regardless of the presence or not of an oil cooler.
I say that the engine is air cooled, not oil cooled in that the main cooling for the cylinders and the heads is from the external finning; while there are obviously oil galleries within the engine, they are really best thought of as being fairly small bore tubes for getting the oil from A to B rather than all enveloping jackets like you find in liquid (whether water or oil) cooled engines, particularly ones that may be left standing for extended periods.
A related comment from me on the use of heat from the oil to warm the footwells: it should be a perfectly good thing to do in hot weather but you probably don't want to take any heat away from the oil in cold weather. This may not be the ideal arrangement! 12V socks or insoles are your friends for driving in proper low temperatures.
Like TimG, I live in the North East of Scotland so high ambient temperatures and heavy traffic are not usually a great worry but I have driven in 35+ degree (Celsius!) heat both at speed and in appallingly heavy slow, stop start traffic when across in Europe and have still never had the skip fire kick in (my car is a 2012 without the cooling pack which I've never felt a great need to get fitted). Saying that, from talking to the engineers at MMC back when the cooling pack was a new thing, they said that at speed the ducting actually serves to give more even (read better) cooling of the cylinders with the fan only having a beneficial effect at low speed or when stationary. Turning an air cooled bike V-twin through ninety degrees and sticking it out the front creates different cooling in the air stream from its original design parameters, not necessarily better: you have to assume of course that any attention to air flow was given at the design stage in the first place!

Thank you both for your comments!

My 2013 M3W was often driven in hot conditions and had to suffer stop and go traffic at temperatures close to 40°C. Never went to skip fire mode (I do have the city drive fan installed)

I wonder if additional oil cooling is needed at all. Good quality oil will do the trick I assume.

If the cooling kit was installed correctly with the re-flash of the ECU then the fan works automatically and skip fire is actually disabled.
I think you're right about the good oil: with 6 litres of synthetic oil and 3000 mile changes hot oil isn't really a great problem.

Ditto, thank you for these comments!

My lay understanding is that S&S isn't worried about the high oil temperatures reached through normal operation. The engine can handle it. The issue is the oil. Each time it reaches a certain temperature, its lifespan is reduced necessitating shorter interval changes. An oil cooler would therefore extend that interval.

My understanding too is that once oil heats, say above 225F, the engine loses 20% hp, but no damage. So keeping the temps in the 170F range would preserves consistent power delivery...or so say the Porsche air-cooled guys.

IF both statements are true, is the greater risk in oil not achieving, say 170F quickly or in exceeding 170F on longer distance rides? I guess I'm having trouble understanding how a cooler which is thermostatically controlled and keeps temps at a consistent 170F or so operating temp can be anything but helpful??

I agree with you that our engines are essentially air cooled not liquid cooled. V-twins get very hot top ends. And absolutely having the engine transverse mounted versus in line gives better air-flow past both jugs, versus only the front.


You are absolutely correct you want oil to reach operating temperature for both flow and to evaporate the nasties. Hence my using a temperature controlled bypass. I do not want cold oil going to a cooler, and I do not want the extra back pressure.

We all drive in different climes and settings. I moved to the mountains of Virginia from Oklahoma. One having lots of going up and down mountains to the other flat but HOT.

I think it is also important to the recall the size of engines in the amount of heat produced. My wife's heritage has a twin cam 96ci and even with an oil cooler the oil tank runs 230-240f going down the highway. My road king is 107ci and comes factory equipped with an oil cooler and the 107ci tour glides have also added water cooling to the top end. Our M3W's have a 124ci engine which is almost 30% larger than my wife's bike.


The urban fan only activates at less than 10 mph were the ambient airflow past the engine is becoming insignificant. As I had previously mentioned on the V-twin forums this is often a heated debate (pun intended). A cooling fan for the jugs OR an oil cooler. Ultimately it really depends on what kind of driving you do and in what climate. There is no right or wrong answer.

You folks from the US are most likely much more familiar with the limitations of a S&S or Harley type V2 so no need to give you advise on this type of motors.

My practical experience is limited to some 15.000 miles on a 3Wheeler.
Maybe the best improvement is to eliminate the reduction plates in the exhaust pipes. That gets the engine free breathing, adds torque and horses and brings the temperature down.

Wish you many happy and troublefree miles!

Removing those baffles will reduce cylinder head temps? That is a good bit of information!
Thank you.