67bmer

I just got a new used Cayenne and want to replace all the oils. I found this very interesting. I am an aerospace engineer and have been thinking about motor oil all wrong. Thinness is good and thickness is bad! I did not realize that oils get thicker as they get older. I was also skeptical of the 0W-XX. I have even seen people on this forum complain that Mobil 1 is "to thin" compared to other oils...

http://www.bobistheoilguy.com/motor-oil-101/

Some people have said they use thicker oils because they only use their cars every 2, 3 or 4 weeks. They are afraid that thin oils will fall off the engine parts and result in a lack of lubrication at startup. Think about your lawn mower over the winter. I gets gummed up solid. The oil and fuel thicken over time resulting in engine failure. Anyway, oil on the surface of parts does not lubricate. It is the FLOW of oil between parts that lubricates. Thick, old, waxy oil can only be bad.

I have seen several car owner manuals that are now stating that oils do not need to be changed but every 7,500 miles or more. The same manual also states OR every 12 months, whichever occurs first. My feeling is that you can probably go 5,000 miles on the average (in a sports car) but you must change your oil in the spring time at a minimum, particularly up north. Oils form waxes in icy cold weather. There is a permanent thickening of the oil.

Some automotive manufacturers are backing down on oil change intervals to 5,000 miles or less and some advocate changing the oil at least every 6 months as well. I think this is because of the tendency for oils to thicken in very hot engines (not ambient conditions, just hot engines). Also because of thickening from the cold of winter and from sludge build up that cannot be filtered out.

I truly believe that oil is much better being too thin than too thick. Over the years we have been going to thinner and thinner oils despite hotter engines with turbos and the like. The tendency is that people figure they need a 40 grade oils but then use a 50 instead. Better thinking is that if you think you need a 40, use a 30 grade oil instead. I firmly believe this based on all I know about oils.

As it turns out synthetic oils do cling to parts better as they have higher film strength than mineral oils. Synthetics are thinner overall. They have greater slipperiness. Yet they stick better to engine parts. Again, this concept is the opposite of normal thinking.

bigbuzuki

I use Mobil 1 0w-40w.
I'm a believer because of 100,000 plus miles, and no engine issues.

mudman2

I went 130K miles problem free with 0w-40 using the Porsche Dash oil change warning to sent me to the dealer

hahnmgh63

It's not just about being thin or thick, if that was the case wouldn't WD-40 be better? It is the Shear strength of the oil. It is extremely difficult to get a high shear strength with a very thin oil but it can be done within limits of price & technology. I am also and Aeronautical Engineer and if you are thinking in terms of the thin Fully Synthetic oils that go into jet engines,axial flow Turbine engines have almost completely different lubricating needs, reciprocating internal combustion engines have very unique needs. But I do agree that thicker is not better. You can get higher Shear strength easier with a thicker oil but you also get startup (especially when cold) oiling issues, increased drag, etc...

philg3

All this is interesting in theory, but I'll leave it to the Porsche engineers and stick with oil specifications in the manual. Used Mobil 1 0-40 in 2004CT, and no engine problems. Now using Mobil 1 5-30 in CV6 and CD, and expect both to perform well. Why second guess the manufacturer? I really think they know what they are doing, other than the coolant pipes, drive shaft, water pump, A/C blower, etc.

BTW, really looking forward to the oil changes in the CD -- all under the hood -- extract the oil, and swap the filter w/o ramps or removing bottom panels.

Slow Guy

There was a post here not too long ago from a Porsche Master Tech, I'll see if I can find it.

Found it, post #89
https://rennlist.com/forums/porsche-...ht=oil+cd+tech

mcbit

Mineral 10w 40 took my Landcruiser FZJ73 to over 320,000 km before I had to replace the valve stem seals which sealed the whole thing up tight again. This based on 5,000 km oil changes.

Mobil 1 has taken my CTT to currently 194,000 km with no issues on the locally recommended 20,000 km oil change schedule. It uses around 1 litre of oil every 4,000 ish km and this hasn't changed in the last 110,000 which I've driven. Oil and car manufacturer's do not just pull these numbers out of the air, they are the results of extensive testing; it is not in the interests of either party to have early engine failures due to over the top claims on oil change intervals.

Aside from the occasional cylinder scoring issue, which i believe is more to with a block manufacturing flaw than oil, there seems to be very little evidence of early failure in these engines.

Lexlthr

Question:

I have a 06' Cayenne S. I only put about 3-4000 miles on it a year. Would you recommend doing a oil change yearly or wait until I hit the amount of miles stated in the manual? I use the Mobil 1 recommended in the manual.

philg3

Very good info posted by GNAT on 6speedlonline.com -- nice pictures -- he drained from the bottom rather than using an extractor.

http://www.6speedonline.com/forums/c...hange-diy.html

Used an extractor (hooked up to an air compressor) on my 2012CV6, mainly because the drain plug was at an angle (not straight down), and I thought it would create a mess. Extractor got most oil (took about 30 minutes), as the fill amount matched the spec's in the manual. 2013CD is less than a month old, so haven't done that one yet, but looks much easier -- no ramps -- no panels -- and hopefully no mess.

67bmer

[QUOTE=philg3;10430817]All this is interesting in theory, but I'll leave it to the Porsche engineers and stick with oil specifications in the manual. Used Mobil 1 0-40 in 2004CT, and no engine problems. Now using Mobil 1 5-30 in CV6 and CD, and expect both to perform well. Why second guess the manufacturer? I really think they know what they are doing, other than the coolant pipes, drive shaft, water pump, A/C blower, etc.

I agree for the most part. It just changed the way I thought about motor oil because I had never designed an engine. I was always skeptical of the 0W-XX formulas. Sometimes its hard to separate the marketing hype from the engineering reality. BMW keeps extending their change intervals and I just have not seen any data to support it. Mike Miller has done an oil analysis after 10,000 miles on RedLine oil and claims that is a good "safe" interval for his car/driving.

The key points were:
1) they are designed to operate at 100C and with a specific oil viscosity at that temp, i.e. 10. Its the cold thick viscosity that one needs to worry about, not the hot thin viscosity. Which the Porsche manual basically states, although its easy to gloss over that part!!!
2) the problem with oil is at startup, its to thick!
3) cold weather ages the oil additives and that oil has a shelf life. (I never knew) I have not changed the oil in my Maserati bi turbo in about 5 years because it only gets about 1000 miles a year and I did not think there was a problem...
4) oil gets thicker with age/use and the base oil itself does not change, its the additives. the problem is contamination and age. there is essentially no such thing as oil break-down...
5) all these additives that you see in the store are a joke. Which I always suspected.

I did not see where he addressed sludge, (what it is and where it comes from) that I have "seen" in pictures. I have never seen it in my engines. I have seen varnish in all of them that was mentioned.

bottom line, I think it worth reading to get the proper context of oil and follow the manufacturers oil recommendations, although not necessarily their change intervals. After all, the are in the business of sell performance (correct oil) and cars (long change intervals)...

Slow Guy

I wouldn't attempt to suggest one method over another as I don't have a CD but I would most definitely (if it were my vehicle) attempt a evacuation method followed by a drain plug removal to verify for myself. If there was anything less than .5 qt after evacuating I would most likely only use the drain plug method every 2 or 3 changes.

FWIW, the 993 oil system leaves about 2 full qts. in the lines/oil cooler after draining the oil, you would have to disassemble the oil lines (at least at the thermostat end) to get all of it out and that would be a very impractical task. The 993 holds apx. 12 qts.

mcbit

As an end user of industrial and marine diesel engines I can state that in general manufacturers specify no difference in running hours between overhauls for synthetic and mineral oils only a difference in the frequency of oil changes. On our marine engines we use oil analysis as the basis for oil changes and overhauls.

In the case of high performance petrol engines, synthetic oils are better suited to withstanding the pressures induced in the barrier film on highly stressed bearings and as an added advantage the reduced drag characteristics resulting from lower viscosity and better lubricity allow an engine running on synthetic oil to benefit from increased power output and lower gas mileage.

philg3

Good point. There is an art to the extraction method by moving the hose around at the end when it's sucking air, to ensure that the hose picked up most of the oil. As I did in my 2012CV6, I will check the refill, to ensure it matches the capacity spec. I know we have one data point that showed one quart was left behind. Anyone else have any data to share on this point?

Appears to me that the tubes in the new C engines (V6 and Diesel), were designed for extraction since there's no dip stick, and that Porsche dealers (at least some, if not most) are now using the extraction method. If this is the practice at your dealer, requesting a drain from the plug, and an additional X# of minutes to get every drop out would likely be met with a blank stare. Bottom line: It's going to be extraction no matter what you request, if that's their practice.

Another point of interest is that according to a few posts, some Porsche dealers are refilling with weights that do not meet the C30 spec (spec says 5W-30 in the manual).

If you do it yourself, at least you know what's been done.

gnat

Thanks for the plug Phil

I've had two dealers tell me they are using 5w40 for the CDs, but its still the Mobile 1 ESP which I believe is C30. I believe there are VW 507.00 oils in different weights too.

There are two cases I'm aware of where DIY extractions left a bunch of oil in CDs (our own Greg and a poster from GA on renntech). Since I hope to hang onto my CD for a long time (12 years and counting for the wife's 996) I'm concerned about how well the extraction method gets the bad stuff that settles to the bottom. On the flip side, extracting would save a 70mi round trip to my brother's place...

Until I'm out of warranty I'll only use what I have MFG documentation stating is acceptable, after that I generally tend to stay with what's working unless there is a compelling reason to stray.

grohgreg

Yup, I qualified my extraction experience by stating that it was a learning experience; new car, new extractor, first oil change. My error was in using the largest diameter tube that would fit into the engine extractor port. It was such a tight fit that I was unable to move it around to get the last of the oil oil. Hindsight is 20/20.
More important than the weight, is the C30 rating itself. Think of the C as representing compression, not unlike as in the API service labeling system. It follows that 30 is the recommended cold viscosity. As I've written before, diesel-spec oil has an additive that holds unfiltered diesel particulates in suspension, thereby preventing their settling to the bottom and forming "sludge". These suspended particulates are what turns diesel engine oil black so fast. Use gasoline-spec oil in a diesel engine, and risk of sludge accumulation rises dramatically. What probably separates C30 from standard diesel oils is its ability to lubricate effectively in higher engine temperatures. Diesels historically ran much cooler, using thermostats from 70C to 85C. This new generation of "clean diesel" is engineered to run at 95C, which by association means comparatively higher engine oil temperatures as well.

As for US Porsche dealers who ignore the C30 spec, 2013 is the first year their service departments have dealt with diesel engines. It's quite possible they arbitrarily assign techs to CDs, regardless of whether they've yet received the appropriate diesel certifications.

//greg//