"Search" What am I doing wrong

I wanted to see what kind of oil pressures you guys see at various rpms. I thought I remember seeing a thread on oil pressures a while back. I do a search for topics using the key words "oil pressure" and I get: "Does a gun shoot in outer space? " "what type of winter tires do you guys run?" Everything but Oil pressure. I quit looking after 20 pages. Am I not putting in enough info in to get a good search or something? I'm not a computer wiz, so I maybe I'm not understanding the search engine logic. While I have your attention, I noticed my oil pressure drops to around 4.0 on the guage a 3,000 rpm and goes up to 5.0 when I increase rpms. I never paid attn. to it b4, but does your go down to 4.0 w/the rpms around 3,000?

Cold engine all engine speeds: 5 bar Warm engine idle: 1.5 bar+ Any engine speed above 3,000: 4 bar+ Jim NOTE: If you run 0W40 in hot climates, you may often see < 1 bar at idle. Not good.

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Even with 15W-50, my oil pressure would be aroung 0.8-0.9 bar at idle in the hottest part of the summers here in South Texas.

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Well, I would look into why. Any pressure less than 1 bar is extremely dangerous for your bearings. Maybe your sending unit s not reporting the correct current to the gauge. 15W50 in 100F+ temps for my cars maintain a minimum of 1.5 bar.

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FYI, your's is not much different than mine. Goes to 5 when a little over 3,000, hot or cold.

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My '87 runs the exact same pressure as my 996 did. 5 bar at cold and less than 1 at idle in the heat.

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Oil gauges and/or sensors are not always accurate. The key is to establish baseline readings when your engine is new, and then be aware of any changes you see over time. An indication on the gauge that show less than 1 bar might very well be the same pressure as a gauge that shows 2 bar. Much like many of the 997 owners who think their coolant temp is 175F when in fact it is much higher. If actual pressure was regularly less than 1 bar, I would be very concerned. The lowest actual oil pressure in my 996 in 100F climates was 21 psi running 15W50. It can easily get lower running Mobil Water.

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Yepper, unless they are calibrated on a set interval which obviously they are not. But, many on this board have had less than 1 bar in the southern states. Maybe the gauge is outside of it's efficiency range reading lower than it really is? I am pretty sure this is the case. In my company, you do not trust a gauge in it's beginning or last 10% of it's range. I think this is where the issue is.

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Agree. If in fact, the engine only had 0.5 bar of pressure as some on this board report the gauge indicates, there would be a lot of bearing knocking in the engine. However, running Mobil Water and not maintaining proper engine temperatures can lower the pressure to dangerous levels even in the best of engines. It boggles my mind that people still use this crap in a high compression engine that they claim to care about.

I wish I could "cut the cord" on the 0W40. I use it in the 964 and WANT to believe it's best for the 996, but every time I get ready to change the oil, I end up giving in to the manufactures suggested weight. Maybe I can make myself in the warmer months. I'm lucky in that 80+% of my driving in the 996 is country roads w/no stopping. My temp stays around 84-85 degrees C. When it's cold (less than 20 degrees), it will take my coolant a good 15-20 minutes to even get to 84 degrees where I think the thermastat opens. I think that makes using the 15w50 not as important as I would think when it's 95 degrees and I'm in city traffic.

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First of all, Mobil Water is not the only weight oil suggested by Porsche. Other weights include 5W40 and 5W50 oils. Secondly, your engine cannot maintian 84C with the thermostat installed even in the coldest of temperatures. If that is the reading you are getting, then, either you do not have the thermostat installed, or the reading is wrong. Your engine coolant should be above 84C even in sub zero tempratures within 15 mnutes, just idling.

Well, that's what it says. It runs in the upper 80's in the summer and will get up to 100 or higher idling at traffic lights in the summer time. Even when I get off the HW and into my neighborhood, hitting stops signs and doing 35 mph., it will jump into the 90's. But when I'm tooling down the HW at 70 w/no traffic (which is most of the time), it's running 84-85 degrees C.

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Where are you getting the reading from, because it is impossible to keep your coolant 84 - 85C running the stock cooling system.. The target temps for the computer is 90C minimum. BTW, upper 80's is a hell of alot different than 84.

I've got my temperature guage set for a digital read-out of the coolant temperature. That's where I saw that my car seems happier (i.e. cooler running temps.) cruising down a country road than sitting in traffic. I think If I had to sit in traffic every day, I'd have to go got the constant running cooling fan mod.

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Well, the gauge or the sensor is reporting the wrong temperature. The thermostat does not even open until 83C so it is impossible to run that cool. Out of curiosity, do you sometimes have an idling problem where the idle does not immediately drop to normal but hesitates above 1000 rpm?

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You think the engine coolant temp sensor is out keeping the RPM's up, falsely thinking the engine is cold?

Was looking at my idling rpms last night. They were 800 with minimal surging. Needle is almost steady. Why would 84 degres C be impossible? if the thermastat opens at 83 and I'm driving down the road at 70 mph with good air movement and the ambiant temp is 30-50 degrees? It will bounce 84-85 degrees, unless I get into traaffic or slow down below 50, then it will rise to upper 80's, maybe even 90's depending on how much traffic and how slow. If I sit still long enough, it will drift to 100 and the fan will cut on. The temp guage on the dash coincides pretty close w/the digital readout, just past the 180 degree hash mark. Needle actually rests just right of the hash mark.

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Don't know what to tell you and I don't want to get into the laws of physics, but the coolant cannot maintain such a low temperature even if the outside temperature was zub zero using the stock setup. Based on your theory, installing a 65C thermostat would allow the engine to maintain a coolant temperature of < 70C. There is not enough coolant flow with the thermostat installed and the radiators are not efficient enough. The coolest I have been able to get the coolant was about 86C once the engine was warmed up. This was obtaiined at 70 mph, outside temperature of -10C and NO THERMOSTAT INSTALLED. With the stock cooling system setup (thermostat installed) you may see 88C periodically if your speed is fast enough, minimal load on engine and < 0C. In SC climate, your coolant temperature is more likely to be 90C+ at highway speeds and often will rise above 105C on warmer days and in traffic. However: IF, your readings are close to being accurate, then you must have increased the flow of the coolant. Either a different pulley was installed or the thermostat is not installed. Your comment stating that it can take as long as 20 minutes to get the coolant temperature to 84C makes me suspect you are running without a thermostat. The 3.4 stock cooling system will reach a temperature of 90C from a standing temperature of 0C in less than 15 minutes, easily. The reason I asked about the idle speed was because there have been some problems with the sensor on the 99's. Typically, the problem shows itself with inaccurate readings but also includes a delay in idle speed drop when coming off a higher engine rpm.

1999porsche911 I'll check my idle closely and let you know. Does the relatively quick temperature increase when I'm not "cruising" seem indicative of no thermastat or bad sensor? I always assumed it was a function of poor temperature control on the 1999's due to just the one radiator.

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Your car has 2 radiators and 2 fans. A missing thermostat will increase the time it takes to warm up idling or cruising.

I meant 2 radiators, not having the 3rd.

If there is a substantial increase in the time it takes for the engine to warmup when cruising versus idling, that typically means you have a water pump that is going bad. Not enough flow at low rpm's. You made no mention here that it takes longer to warmup at idle than it does when cruising. (unless I missed it)

I checked last night. Ambient temperature was 61 degrees: Start-up engine temp 17 degrees c After 7 minutes at 70 mph engine temp 84 degrees c next 15 minutes at 70 mph engine temp fluctuated between 84-85 degrees Went thru residential area for 2-3 minutes at 35-45 mph, engine temp goes to 87-89 degrees Back on HW at 70, mph, engine temp 84-86 degrees. Pull in neighborhood for 4-5 minutes at 35 mph w/2 stopsigns, engine temp increases to 90 degrees. Since my only stops are at stopsigns, I sit for only a very short time at idle, but when I do, it idles at 800.