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M1 5w50 is A40 approved for use in our cars. I used it for a few years in mine before switching to DI40 after the CPO ran out. The UOA's were more than acceptable. It was good down to somewhere like -10 or -20 degrees F.
Sub'd. Good convo guys. Baz's details are awesome and I'm not about to go spend time on Facebook so I appreciate the C&P, @smrpr.
I'm about to add the 3rd radiator for autocross and occasional track use, sounds like switching to a thicker oil would be a good idea - 5w50 or so given that winters here are often in the 30s and occasionally down to 0ºF. Our summer autocross events are often in 100+ºF, which is a concerning change form just a handful of years ago even.
So as with a lot of things 997 related it matters if you have a .1 or .2, Hartech's article relates to the .1 M96/97 engines, the later engines have a fundamentally different design.
As I occasionally have bouts of paranoia to rival Bruce (and as I fitted a third radiator last year) I was moved to dive into the parts diagrams and see if the issues that Hartech raised afflict the 997.2 engines as well. So my understanding from looking into this is....
The 997.1 M96/97 thermostat looks like this,
The thermostat (bit with the spring) sits in the hot coolant exiting the engine and when it opens it allows cooler fluid to enter the flow from the right - this inevitably causes some cooler fluid to mix with the hot engine flow before it passes the thermostat as the orifice is round and some coolant enters the flow upstream of the thermostat. Hence Hartech's position that more cooling can actually give you a hotter engine..
The 997.2 thermostat is a different design,
It's designed so the hot fluid from the engine passes through the centre of the thermostat, when it opens the additional fluid enters from the side (the solid 'top hat' portion of the thermostat assembly slides upwards to release the flow of cooler fluid) it does not affect the temperature that the core of the thermostat sees. If you dive into the parts diagrams and photo's of the various covers and tubes around the thermostat you can see that Porsche did some clever routing of the flow around the thermostat to achieve this.
All the above is my understanding and I'm happy to defer to anyone with more experience of these engines cooling systems..
But thankfully it seems my paranoia about adding the third radiator is unfounded, if you own a .2 your third radiator is just adding cooling capacity.
Hope this helps people understand the differences between these two engine types.
From driven’s catalog. Xp6 is a 50W, xp9 a 40w. I apologize for over posting this but most people don’t understand how quickly viscosity decreases with temperature.
This is actually really interesting to see, I kind-of understood how the oil weights worked but its very interesting to see how little difference there is when the engines are hot, thanks for posting.
There are some causes that Hartech has researched in more detail. I have taken a sketch from a document of a supplier that works with Hartech, it could even be that the sketch is from Hartech itself. "E" is the cooling water flow, green is the oil injection, red is the highest load in the cylinder. There are (among other things) two things that are unfavourable:
1. the cooling is symmetrical in both banks. Bank 1 naturally works better because the cool water hits the warmest area immedeately, but in bank two the warmest area of the cylinder is at the top, so the temperature gradient or heat transfer is worsened/not that efficient because the cooling water is "pre-warmed".
2. the oil tip nozzles (green) are symmetrical and good for bank 1, but unfortunately unfavourable in bank 2
All measures that take this warmer bank two into account are therefore expedient.
Last edited by 8x57IRS; 02-23-2024 at 11:21 AM.
Reason: oil/crankshaft
So what is the executive summary here based on the above and BAZ's thesis:
1) When I have my water pump replaced should I have the low temp (165 degree ) thermostat installed? yes/no
2) My car runs alternatively (220 -240ish) a bit hot in 90 -100 degree weather in NJ going 65-80 mph (no track use) - install third radiator? yes/no
3) Currently using DT5-40, previously used Motul 8500 5-40. Iron / Copper wear metals a bit high, but consistent from 15k (first UOA) miles to 50k miles now; Aluminum/Silicon are good. 4k miles/annual OCI, no oil burn/ required to be added. Will see if wear comes down using DT oil per my next (2nd) oil change with DT. Should I go to DT5-50 next change if wear does not come down?
So what is the executive summary here based on the above and BAZ's thesis:
1) When I have my water pump replaced should I have the low temp (165 degree ) thermostat installed? yes/no
2) My car runs alternatively (220 -240ish) a bit hot in 90 -100 degree weather in NJ going 65-80 mph (no track use) - install third radiator? yes/no
3) Currently using DT5-40, previously used Motul 8500 5-40. Iron / Copper wear metals a bit high, but consistent from 15k (first UOA) miles to 50k miles now; Aluminum/Silicon are good. 4k miles/annual OCI, no oil burn/ required to be added. Will see if wear comes down using DT oil per my next (2nd) oil change with DT. Should I go to DT5-50 next change if wear does not come down?
Do you drive the car in the winter is the first question? If no, then my 2 cents say.
yes on LTT
yes on 3rd radiator
Yes on moving from DT40.to FR50. DT50 is NOT the one you want as that's a 15w50. FR50 is the 5w50 and what I use in both my 997.1s now.
I was also thinking that I should've indicated that I do drive electively in cold weather (to full warm up +) to keep things moving and my therapy, but not below 38 degrees. And, it is in my garage where it does not get below 40-45 degrees.
I could change to cold weather oil 5-40 to warm weather oils 5-50, but may not be necessary given the above where it is almost never exposed to freezing (32 and below) conditions/environment.
Q: assumption is that the FR5-50 would make the oil run cooler in my extreme example (?) My next oil change is coming up as is warmer weather - maybe will go to the FR 5-50 and report back. I only used DT5-40 the last two OCs as of now.
I was also thinking that I should've indicated that I do drive electively in cold weather (to full warm up +) to keep things moving and my therapy, but not below 38 degrees. And, it is in my garage where it does not get below 40-45 degrees.
I could change to cold weather oil 5-40 to warm weather oils 5-50, but may not be necessary given the above where it is almost never exposed to freezing (32 and below) conditions/environment.
Q: assumption is that the FR5-50 would make the oil run cooler in my extreme example (?) My next oil change is coming up as is warmer weather - maybe will go to the FR 5-50 and report back. I only used DT5-40 the last two OCs as of now.
You can run the FR50 5/50 in that case and don't need to change it based on the seasons. Remember, the cold viscosity index of both DT40 5w40 and FR50 5w50 are the same at 5 so when the engine is cold, the oil rating is the same. The 50 just has a higher viscosity when it's hot and the increased film strength. Although we live in SC, we drive our cars when it's 40 F too - not on the few days it's 20 F.
02-20-2024, 01:47 PM
