Use your laser heat gun on the oil pan. It's a pretty good indicator.
The importance of oil Temperature in Determining what Viscosity of oil to run.
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The Macan has blue bars above the temperatures to remind you to take it easy until temps are right of the blue bars.My M139 Amg and K20 would never see full throttleAmg has a neat little indicator that makes the oil number blue "for cold" and after 167f it changes colors. The K20 doesn't have that but with integrated headers it hits 160f very fast.
OVERKILL
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My M5 had a variable redline that allowed you to explore more of the tach as the engine warmed.
yes but that has to do with thermal expansion of all parts, and not oil viscosity.
It likely means the same in the macan
OVERKILL
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I assume they figure viscosity in there as well as part of the reasoning, as they also include oil temperature instrumentation.
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Remember that oil temp sensors are usually at/near the oil filter adapter, sometimes in the oil pan itself. This temp is just bulk temp which is useful. However a turbo charged engine should have one on the oil drain from the turbo. That temp may scare you a bit more. I put a temp sensor into the cast aluminum pan on my 1.8t AWM. It usually read between 190 and 210F unless I was really "spirited". Water/oil cooler, and I'd wager that a majority of the heat came from the turbo. It would have been interesting to put a thermometer on that turbo oil drain. However it was also water cooled.
yes but oil temperature is related to engine temperature as well, the expansion of rods and crankshaft is totally oil cooled
OVERKILL
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Yes, though my experience with this engine is that oil temperature takes a lot longer to come up than coolant temperature. This is unlike my two HEMI's, where, with the coolant/oil heat exchangers, oil temp very closely mirrors coolant.
Yes, and that's why they have to take oil temps into account for the redline shift.
My Alfa Romeo manual states I'm good to go (full send) when the coolant gauge starts to move, but I always wait until coolant has reached normal operating temp. that car has a coolant/oil exchanger.
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Romping on anything other than a fully warm (oil and coolant) just seems like mechanical abuse.
abusing my own pocket book too, I don't tend to trade in vehicles.
Patman
Staff member
When I think back to all of the times I let my cars cool down for two hours before making a quarter mile pass at the track it makes me cringe
Especially when I was doing it on a very cool fall day when it was barely 40 degrees outside. I did that a lot with my 95 Trans Am and my Paxton Supercharged 87 Mustang GT. In both of those cases they would run almost two tenths quicker when stone cold vs fully warmed up. I was happy when I got my first LS1 powered car (my 98 Formula) and found out that it actually ran quicker hot than it did cold, so I could make pass after pass and it wouldn’t get slower.
Water-cooled turbos have relatively low oil flow. Traditional journal bearing turbos don't need much oil for lubrication purposes-- the majority of the oil flow for such turbos is to cool the bearing housing.
Water cooling the turbo not only improves the turbo life (lower temps and more uniform temps), but it reduces overall engine pumping losses by lowering oil demand.
Unless it's a track day situation, your water cooled turbo street car isn't cooking the oil nearly as much as one might think. Most of the heat it going on the exhaust pipe and another big chunk is going out the radiator.
In your particular case, 210F is all day and forever acceptable oil temp, and brief excursions to 240F or so for "spirited" driving aren't making a huge dent in the oxidation rate of the oil.
There have been studies on journal bearing cavitation, and it can happen under certain conditions. Extreme cases will pit and erode the surface of the relatively soft bearing material.
I have the paper saved someplace. If I find it I'll post the conclusions. I did some searching into it when there was a theory that journal bearing cavitation was causing the Ford Coyote "BBQ tick" - ie, the ticking was cavitationair bubbles imploding. . One of the conclusions the study had was that thicker oil was more likely to cause cavitation. The Coyote BBQ tick only happened after the oil warmed up and got thinner, so goes against the cavitation study. Also, the BBQ tick will go away instantly if as little as 150 ml of Ceratec is added to 8 qts of oil. That's why I think the tick is caused by the friction level between moving parts. Ceramic is a friction modifier.
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What about the windage from the crank spinning?
But wouldn’t this be cavitation bubbles that were generated in the oil pump pickup itself and then pumped to the bearings, causing it to be aeration? Thanks…
Cavitation is not a “vacuum” phenomenon at all. But it is related to pressure.
Cavitation is caused by a low enough pressure in a liquid to cause gas bubbles to form, and when the bubbles become exposed to a higher pressure region, they implode and collapse. That action can cause cavitation erosion of surfaces. The inlet pressure doesn't necessarily have to be a vacuum (ie, below Atm pressure, or zero gauge pressure). But it could be below Atm in some cases. Air bubbles form based on the vapor pressure of the liquid.
So in a pump, the bubbles can form on the low pressure suction side, then become pressurized on the higher pressure side of the pump and collapse, causing a mini implosion that can do damage over time.
The area where oil enters a journal bearing is at a lower pressure than the supporting MOFT wedge. Cavitation can occur in journal bearings under the right conditions. Journal bearings essentially act like mini oil pumps. The side leakage flow they have is a combination of self pumping and the oil supply pressure. A journal bearing will self pump oil through itself even if it's feed an oil supply at zero gauge pressure (ie, Atm pressure). They flow more when the oil supply is above ATM pressure.
So in a pump, the bubbles can form on the low pressure suction side, then become pressurized on the higher pressure side of the pump and collapse, causing a mini implosion that can do damage over time.
The area where oil enters a journal bearing is at a lower pressure than the supporting MOFT wedge. Cavitation can occur in journal bearings under the right conditions. Journal bearings essentially act like mini oil pumps. The side leakage flow they have is a combination of self pumping and the oil supply pressure. A journal bearing will self pump oil through itself even if it's feed an oil supply at zero gauge pressure (ie, Atm pressure). They flow more when the oil supply is above ATM pressure.
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The AMG M139 turbo is cooled by air, water, and oil. Daily driving oil temps are 160-170f. Your average grocery getter with a turbo isn't going to endanger oil temperature. If it is power dense like the M139 then manufacturers incorporate proper cooling.
All this.
We see cavitation in fuel injectors operating at 2200 bar. It only takes a big drop in *relative* pressure to create the vapor. Extremely fast changes in direction, changes in pressure, and such can all cause cavitation.
For example, where fuel has to make a high speed turn to flow out the spray holes in the injector, the sudden turn will drop pressure because the fuel has mass and inertia and it doesn’t want to make the turn. As a result, the fuel at the inside of turn can experience a rapid drop of pressure and form vapor (even though on paper you have 2200 bar pressure in that nozzle sac). And that vapor collapses just as it enters the spray holes and starts to straighten out. Under abusive test conditions, it will eat through the injector nozzle from the inside out.
A follow up with the info on journal bearing cavitation (for @SubieRubyRoo), and to add to my post 57. Google search for "The effect of viscosity on the cavitation characteristics of high speed sleeve bearing" to find the bearing cavitation study PDF download.
From another source:
Fig 1.2
"When the bearing operates in the hydrodynamic regime, a fluid pressure builds up in the bearing by a converging geometry effect in the lower portion of the bearing, shown in Fig. 1.2. Following the minimum clearance portion of the bearing, the clearance increases (the surfaces diverge). This diversion results in a pressure drop in the lubricant that leads to cavitation (this portion of the bearing is often referred to as the ’cavitation zone’)."
From King Bearing - Info on journal bearing failure modes; cavitation erosion.
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