Oil weight, temperature, oil pressure, question #1279272

Oh yes! Another question... I have been looking for an answer, but I really just got sucked into a million "almost my situation but not quite" post. So, here is my current state: Car is a 2001 C2. 140,000 miles. "hi mileage". The PO used 5w40 synthetic. I bought her 2k miles ago. I slowly have found her "limits", both mechanically and performance-wise. I live in Oklahoma, just north of Texas in the USA. Temps have been between 105*F and 85* daytime temps. Oil pressure is good. pegged at 5 (bar?) when warming up and goes down to about 3-4 on freeway when warm. Now, at IDLE she reads above 1, when really warm after a hard run on a hot day, she reads exactly 1 bar. I think this OK... I would love confirmation... the guys I took my car to for a PPI (post) were the best in tulsa yet they were so lame that they only told me things close to the "the sky is blue" level of obvious... No answers to more technical questions. I assume this is a no news is good news situation? When crusing at 75mph on a 90* day, the HVAC hack reads right around 95*C. I hear this is the targeted temp by the computer? When I ran her HARD the other day, private area, 30 mins of 80% driving... temp went up to 107*C Highest ive ever seen... The oilpressue was a bit low as it was right on the 1 at idle. PO used 15w.50 synthetic. I am thinking that next summer I should run that weight oil as it might increase oil pressure? As for the 107 degree temp stuff, I am thinking that is the nature of the beast... She cooled down, but slowly and only once I got off the throttle. I am wondering what temps you guys are seeing on the track via the AC hack... Sorry for TMI

I think 1 bar at hot idle is just fine, maybe perfect. I wouldn�t worry about switching to a thicker oil to increase your pressure, since you�ll maybe only get 1/4-point by doing so. You can achieve 1/4-point or more just by hitting the AC bottom, which raises idle from 675 to 800 RPM as well as turning on the low speed fans (helps cool your engine). I also don�t put much stock in the HVAC hack that displays engine coolant temperature. In my car, and some others, it reports higher than what the computer sees. As long as your fans are working properly, you should have any overheating issues. Mine was as high as 117C (242F), but the ODBII dongle was showing about 101-102C at the same time.

I have noticed a big influence between temp and oil pressure. When my temp gets between the 8 and 0 it's fine , as soon as it crosses the 0 then the pressure drops. Now how accurate that is im not sure. I do notice my OP gauge fluctuates a good bit. Also if you havent clean your radiators, that will help your temps and thus ;your OP. There is also an upgrade oil pressure relief valve 997 to 996 that would also help idle pressure. before my oil light would flash if I ran it hard, after cleaning and new oil and OP valve its very stable. I think cleaning made the biggest difference.... there was a LOT of crap in between the cond and rad.

I was on 0w40 Mobile 1 for the past couple years. When I did a hot run up the canyons, and then coming to a stop, I started getting a very noisy ticking from the right rear of engine, plus my oil pressure gauge dropped to .5 and my oil light came on (it kind of came out of nowhere a year after having the car). Freaked me out the first time. But a little rev of the engine and the pressure would go back up up (or as others have said, simply turning on the AC) and light would turn off. Ticking would also go away with a little RPM boost. After it cooled a bit, no issues with low pressure and no issues with ticking. Only happens when engine is at max op temp (needle on right side of 0 in 180, where it will stay put with aggressive drives and elevation gain). I tried overfilling and underfiling oil. Made no difference. And I just had the oil changed and we decided to go 5w50 (which is what Porsche now specifically recommends for the 996 now-a-days). It had absolutely zero effect after a run up the canyons in high 80s temps this past friday. I was really hoping a thicker oil would help keep up pressure overall and help pressurize the lifter. But nope. I would be wary of trying 15w50 personally.

Quotes source post: 19638687

Do you happen to know the viscosity numbers at 100C for the 40w and the 50w you tried?

I run 5w40 and experience the same situation....perfectly normal.

Quotes source post: 19639457

I don't but both the 40 and 50 are Mobile 1. Looking at their website, i found this, which has a 100c listed in it - no idea what it means though. 5w50 Kinematic Viscosity @ 100 C, mm2/s, ASTM D445: 18.6 0w40 Kinematic Viscosity @ 100 C, mm2/s, ASTM D445: 13.8

My 99 had ~143k miles when I bought it about 4 years ago. The oil pressure when hot was at or below 1 bar with the unknown oil that was in car when I bought it. I changed oil to Redline 20W50. The oil pressure at hot idle went up to about 1.5 bar. Now the car has ~178k miles and is still going strong. The oil pressure gauge hasn't been working lately due to a bad sending unit. That is getting fixed today. I will report the oil pressure in a day or two, once I get the car back. P.s., I live in Southern California so cold starts are not a problem.

Quotes source post: 19639537

The higher the number, the thicker the oil is. While the thicker oil won�t reduce temps, it should give you a little tiny bit more oil pressure. Redline is close to 21 for Vis@100C, so that oil should also give you a tiny bit more pressure if you switched to it. The thing about Mobil 1 is that it tends to thin out over time, with use. That�s not a huge problem, as thinner oil can slightly improve fuel economy (a tiny bit - everything here in this convo is tiny like my brain). But it�s just good to know if you run longer intervals (not recommended) or you are chasing every bit of pressure. Edit: I�ll add that viscosity changes are much more dramatic at cold temps than hot temps. See chart image.

When measuring OP at idle, mentioning whether the AC is on or off is important. The extra 100-150rpm idle speed makes a significant different. On my car, after a hard run, oil pressure will be around 0.85-0.9 bar at idle with the AC off / 1+ bar with the AC on. The rule of thumb is 1 bar per 1000rpm. I think @Porschetech3 mentioned that as long as you have 4.2-4.3 bars past 4000rpm, you're good and do not need to switch to 5W50.

I have my car back and oil pressure at idle is 1.1 bar when hot. I had driven about 30 minutes. The temp gauge needle was mid-0 on the 180. The idle speed was 650 RPM. FWIW, the RPM does not change when turning the AC on or off.

Yep, the published test/spec for oil pressure from Porsche is above 4 bar at 4k RPM with 40wt oil at 90C oil temp, ( measured at the head/oil sender port for 5 chain engines) The published specs for 3 chain engines is above 3.5 bar at 4k rpm with 40 wt oil at 90C oil temp ( 3 chain engines use more oil for vario-cam olus activations) There is no Published specs for oil pressure at idle ... No harm in having higher than spec oil pressure with a higher viscosity oil( just a loss of efficiency),higher viscosity should be used for more demanding operations with higher heat( high performance/tracking)...the lower viscosity oil formulations are primarily for gas mileage/emissions reasons, but protect very well, but are not for the most demanding operations

Quotes source post: 19641685

Thats interesting. My �99 goes from 675 to 800 when I turn on the AC.

Quotes source post: 19641749

[QUOTE=Haalex;19640971]On my car, after a hard run, oil pressure will be around 0.85-0.9 bar at idle with the AC off / 1+ bar with the AC on./QUOTE] I'm curious, how does your pressure look if you at high temp, and taking hard turns (left or right). Have you watched the needle? Mine is massive drops in pressue, to just 1 or a hair below, and been a long long time of trying to sort it out, or find someone who has the same -- mine too runs at just below 1 after a hard run. Yes i was surprised by his needle not moving either, mine jumps too when AC is turned on (pretty sure that's standard).

Quotes source post: 19641790

I actually posted a few messages on your topic, since I was experiencing the same issue (large drops in both RH & LH turns). In my case, it turned out the driver's side scavenge pump had been installed the wrong way. Once corrected, I stopped seeing those drops and oil pressure is now steady as a rock in turns. Oil pressure under 1 bar with AC off after a hard run seems common on M96s.

Quotes source post: 19641815

Oh right. Well not my issue sadly. Though i was amazed at how many people were affected by that!

Thanks everyone! Also thanks for the chart. I love a good chart. Seems I am within spec. This car has given me a lot of "first" and I am still "taking her temperature" perse (no pun intended). She runs so damn well, better than several other lower mileage 996s I drove before settling on this one, and I would be surprised if there was anything wrong with'er. I am going to have to whip out the OBD2 reader soon. I wonder if the sensor the HVAC looks at is the same as the sensor the OBD2 reader will be reading. I need to learn how the computer actually works on a 996. Knowing porsche, there are like 4x different "coolant temp sensors". I also have the durameteric tool and have yet to use it... Maybe this is a good chance!? Too bad I can't recall AC on vs AC off idle pressure, but I do know it was at or a hair above 1 bar. @Haalex , thanks for the info about OP @ 4000k RPM. I feel like that's when the 2nd cam start engaging and real power starts to be made and full cam ON starts at 5k. I will check what OP I am getting @4k tmw. I KNOW she is right around 4-5, but I will confirm next time she is warm and the next time she is HOT hot. Finally, about turning and OP drops, my car has the FVD deep sump kit. I have been taking a high speed clovers, all 4x turns, every day on my way to and from work on the highway, and I have been thinking about how the OP may drop during said semi-illegal hi speed turning. The previous owner (PO, not OP lol) was slightly tracking the car so the 996 has a few mods to counteract this. I will return with some info soon after work tmw! It will be hard to get that heat up tho. Oklahoma just went from 100*F days with +70* dew points down to 50*F this morning! It only took one week. I hope we get one more last super hot day so I can see how she handles it. Thanks to everyone who replied! You all rock Peace

Here you go. Water temp, oil temp as well as oil pressure at idle in my garage after a 1.5 hour drive on local roads and highways. I highly recomend contacting @Coopduc who built the oil temp gauge to get one. Pretty handy tool. I was running 12 qts of Driven DI40 in the engine using a 2 qt deep sump and the UAOS Track. My next step is to run DI50 during the warm weather months and on the track, with DI40 during cold weather months.

For those of you looking for what oil weight and oil ingredients you probably want to consider for your 996, you may want to read thru this thread. Alot of tests and discussion on weights and moly content. Best advice I can give any M96 owner is don't skimp on what oil you run and performing oil changes in your M96. https://rennlist.com/forums/996-foru...pca-video.html

Quotes source post: 19638687

The 15 is the cold temperature weight. It's the 50 that is the weight when the oil is hot. Many people confuse those numbers. 0W 50W would, in theory , yield the exact same oil pressures when hot as does 15W 50W. Lastly, the dash gauge may not always be accurate, or more importantly, the oil pressure sender may be the real issue.

Quotes source post: 19644165

+1

Quotes source posts: 19644278, 19644278

Agree True - it can easily be off by as little as 1/4-bar even for a gage that�s considered to be working fine.

While it is true that a 0W-50 and a 20W-50 is the same viscosity when hot........How they get there is VERY different !! A 0w-50 uses a base oil that is OW weight, then adds Viscosity Improvers ( Polymers) that get thicker ( grow bigger) with heat.... A 20W-50 uses a base oil that is 20W weight, meaning it has/uses less Viscosity Improvers ( Polymers) to get thicker ( grow bigger) with heat...so they can't break down as much.... But the Viscosity Improvers ( Polymers) are what beaks down from mechanical shearing , and why some oils loose Viscosity after hard use...Timing chain systems can literally chop-up the Polymers and loose Viscosity.. The old straight 30 weight oils or straight 40 weight oils were deemed to be a bit too thick in extremely cold temps, like way below 0F , but 0-20 weight oils are designed strictly for fuel economy and emissions.. The Top Fuel Cars use a "straight 70 weight" high performance oil with no Viscosity Improvers, to handle the 10K HP and high heat/shear loads... Also as another point of reference the newer Boss 302 has a 5w-20 oil as factory spec unless you chose the "Track Pack", then it calls for a 5W-50 weight oil, same exact engine, just a tougher oil to go with the bigger brakes and better suspension system on the Track Pack Option...