Oil Question

What is the oil weight an indication of? And what is the second number 30, 40, 50? 0W-40 is currently recommended by Porsche but do you take into consideration climate conditions, altitude and how aggressively you drive? Thanks, Rob

5w40 is the recommended oil...

That's contrary to what I've been told by a Porsche service manager.

Here's how I understand it. The numbers indicate a specific viscosity or thickness of the oil. The lower the number, the thinner the oil. Oil viscosity is alo affected by temperature. The hotter the temp of the oil, the thinner it gets. In the old days, engine oil had a straight viscosity number, such as W40, and was subject to change depending on temperature. It will get very thin when hot, and very thick when cold. Modern oil has a range of viscosity which indicates it's ability to adapt to the changing temperature by maintaining a relatively constant character within its temperature range. The 2 numbers, for example W0-W40, indicate the viscosity range of the oil while it's within its operating range. At the maximun temperarature of it's operating range, 0-40 has a viscosity equivalent to a straight W40 viscosity oil at that temp. It tries to stay thick despite the high temperature. Conversely, at it's lowest temperature range, it will have a viscosity equivalent to a straight W0. It tries to stay thin despite the low temp. Obviously, the viscosity range needs to change depending on the operating temp. The oil needed for the Sahara dessert is going to be different from the oil needed for the antartic. I wonder how a C4S will do in the antartic compared to Jame's Bond's Vanquish? That how a layman like me understands it. Maybe a chemical engineer in the group can explain it better. Either that or show how ignorant I truly am .

Palting, Thanks for the response. The reason I ask is that I was going on a 400 mile business trip and my oil level was blinking. I couldn't get to a Porsche dealer so I put in a quart of Mobil 1 5W 30. Logic being that better to have an oil slightly off the recommendation than no oil at all. I'll be taking my c4s cab in for an oil change next week (it has 6000 miles on it). So my next question is this: When I checked the oil level in the car the meter was pegged to the top... kinda odd considering it was 1 quart of oil. Does the dealer calibrate this reading when they change the oil. Thanks again... Rob

Rob, what did your dealer tell you? they changed the recommended oils because of lifter problems... 15W50 is for racing only and 5W40 is what they are recommending these days... that was a service bulleting by Porsche... previous oil recommendations where too thick... as for adding oil... good move... but add 1/2 a quart at a time because when the oil is blinking low I believe you can manage to get into the safe zone 1/4 at a time without going too high as your case.... Peter

Thanks for the info... I will double check the porsche recommendation. 1/4 quart sounds like a plan next time Thanks again, Rob

According to my owners' manual 0W-40 is not even listed as an option and 10W-40 is fine for all temps. Nonetheless, the Porsche dealer uses only 0W-40 and that's the oil that the car is delivered with.

I did a check on the Mobil1 web site (click here and select Which Oil For My Car? on the left....) , and for my car (MY2000), they recommend 0W-40 .

sorry guys, I meant to say 0w40 instead of 5W40... they switched to 0W40. regards, Peter

So just to clarify, Porsche does recommend 0W-40... not 5W-40, correct?

Yes, I've had this discussion before but I can't clearly remember right now... I swear I thought it was 5W40... I'm gonna call my dealer and ask them... and I'll report back here with my findings. regards, Pete

My dealer says 0w40 only. Ofcourse they also told me I could only buy it at the dealer for $8.00 a quart, that no stores carried the european formula. I got it at Auto Zone for $4.20 Walmart has it now too for about the same price.

That's good to know. How often do you put oil in your car before you get a complete oil change? Thanks, Rob

Just to add to everyone's knowledge and to answer the original question... oil "weights" are defined as: XXW-YY Where XX is the oil's viscosity at 0 degrees celsius. YY is the oil's viscosiy at 100 degrees celsius. The W stands for Winter. Therefore the low number is what your oil's viscosity is at low temps (winter) and the second number is the oil's viscosity at high temps. I'm not an expert, but I don't see how it could make a difference if you're running 5W-40 or 0W-40, unless you're maybe running a highly tuned race car.

Approved oils from the Porsche technical service bulletin: Castrol Syntec 5-50 5-40 Mobil1 0-40 Mobil1 5-40 Havoline F3 Synthetic 5-40 Valvoline Syn Power 0-40 Valvoline Syn Power 5-40 Also Mobil Super 10-40 Pennzoil/Quaker State synthetic European formula 5-40 Pennzoil Performax 5-40

Thanks for the info. The only thing I can think of is when warming the car up it would take longer because the viscosity is higher. You don't want to pull a Challenger by running too hot too fast. Under normal driving conditions I wouldn't think it matters. Rob

Porsche switched to 0W40 because they had lifter problems with their cars in cold climates... your right though... it probably wouldn't make a difference unless your driving your car in a -20 degrees Celcius environment... and Pcar drivers don't...