I changed my oil to HD syenthetic this year to help with the summer temps. Problem is that it didnt seem to make the bike cooler. Before I switched over I was seeing a steady 230. Now with syenthetic on a 90 degree day the temp hoovers around 235-240. I seems like the syenthetic is making the bike hotter. I dont want this to turn into an OIL debate. What kinda temp are you guys seeing with HD syenthetic oil?

 

220-240 in 90 degree weather.. Amsoil handles temps of up to 300 so have no worries..

 

+ ! - Amsoil post.....JayStrongHawk

 

++ Amsoil

 

Here are typical oil-temps for my '07 in >90° weather. I'm including CHT info for reference (front cyl. head temp.):

>45mph constant: 200° max (CHT=225-235°)

35-45mph city, mostly moving: Usually <210° (CHT=250-260°)

Heavy stop-and-go city traffic: Max 230° (CHT=270-290° max)

My EITMS activates at 290° (CHT), but it rarely kicks in. It takes a while to get oil temps up to 230° even in the worst conditions, and in two summers it's exceeded that (slightly) only once. I'm also running lean AFR's in the low-end for mileage with the ability to switch to a richer configuration when the going gets slow and hot, and the numbers above are with the leaner setting.

Synthetic oil will help with cooling, but I've seen no evidence that any brand is better than another, although mixing with some specialized racing oils can help somewhat. Any full-synthetic can handle higher temps than a fossil oil because they reduce friction. They also reduce oxidation, but they still break-down exponentially as temps increase, so extremely high temps shouldn't be a comfort just because you run synthetic oil. Keep it sane, and IMO above 230° for more than a few minutes is not sane regardless of what some oil manufacturers claim.

Wind conditions make a difference too, as in a headwind you will normally run cooler, hotter in a tailwind.

IMO every TC engine needs an oil cooler, so if you're the least-bit worried about oil temps, get one. It should reduce peak temps 15-20° and will work even when not moving to some degree by convection.

 

Were your reading with or without an oil cooler ?

Thanks

 

Synthetic oil will not make a bike run cooler.
It is used because it takes a lot hotter temperature for the synthetic to break down compared to dyno oil.

I’m not sure of the exact number but it’s like this:
Dyno oil breaks down with temps above 265
Synthetic breaks down with temps above 300

 

Yeah. I've read quite a few posts where they said that changing to syn oil lowered the operating temps from 230 to 200. For syn oil I might go a few degrees, maybe 5 degrees cooler at the very most. Like you said, the syn oil can handle hotter temps before it breaks down.

The temp I read for dino oil breaking down is 250.

 

Look folks, heat transfer is a function of three basic things. Surface area, type of metal(medium) you are transferring the heat through and the real variable Difference in Temperature (Delta T). For our engines the first two are fixed with the Delta T being the variable. In the summer you have less Delta T and therefore higher temperatures. The other factor in the Delta T equation is the method of heat transfer being radiation or convection(forced flow). When standing still you are mainly transferring heat by radiation which is exponentially less efficient than by convection. Convection occurs when moving air flow past the surfaces causing an increase in the efficiency. Another type of heat transfer is conduction which occurs between two medium in contact. Like through the cylinder walls. All in all when the delta T goes down like in the summer the oil will get hotter.

I am sure the engine design engineers understood this process and designed the engines to handle the normal range of temps in the world. Hot oil is not all that bad and you should not worry until it exceeds 300 degrees F. Just relax and ride the darn things, the oil will be fine.

 

The late model twin cam engines are going to run hotter than the older engines. The displacement increase alone will cause this: from the EVO 1340cc to 1580cc. Also the TC96B engines are working a little harder spinning the two counter balancers.

During the development process for the TC88 engines H-D encountered heating problems. In fact, the TC88 almost debuted with an oil cooler.

From wiki: