Kevin

Basal, you are going to wreck your Piston and liners with 5 weight or 0 weight.. You can run the lightweight oil in the 996TT but not in a air-cooled engine with the piston to cylinder clearances. 5 weight would only be good in Edmonton at Christmas time... With our 80-85 degrees today, you increasing engine wear..

Basal Skull

Okay Kevin, I'll switch back to 15 W 40. I dont mind/enjoy changing my oil (really), I think my car runs better/sounds/behaves happier whenever the oil is new.
I thought the lower number didn't have much to do with how thin the oil got when hot and the higher number was what was important - ie. when warm, 0w40 and 15w40 would be the same, but when cold, the 0w40 was thiner than 15w40? Or is this a missunderstanding?

sfbanchs

thanks theo kevin what is your opinion on motul oil?

dholling13

Motul's products are nice but I wouldn't overlook Redline oils. I use there 20w50 for my car, and it's mostly a track machine now...

Kevin

I am going to be posting a thread about what I think about the latest oil formulations.

Basal, the first number is directly related to the initial start up temp outside. These air-cooled engine need a higher number due to the gap between the piston and cylinder. Wear is accelerated if the oil at startup when the engine and oil is cold and to thin. For many year VW and Porsche required us to use straight 30 weight. 15W-50 is a good choice..

Felix

At what ambient temp is the 15w-50 deemed too thick to use in a cold engine?

Doug Hillary

Hello,
the subject of engine lubricants always seems to produce many fixed positions and I hope the following input may assist with a little more understanding of the wonders of Tribology

1 - Basal Skull - you are correct, a 0w-40 and a 15w-40 lubricant must both be in the viscosity range of 12.5cSt to 16.3cSt at 100C (J300 SAE Classification)
This similarity changes however for these two specific multigrade lubricants at the High Temperature High Shear (HTHS) test protocol temperature of 150C. The 0w-40 oil must have a minimum viscosity of 2.9cSt whilst the 15w-40 lubricant must have a minimum viscosity of 3.7cSt. The minimum HTHS viscosity for Porsche Approval and TSB Listing is 3.5cSt

2 - Kevin - There is no evidence that a 0w-40, 5w-40 or a 15w-40 lubricant will have lessor or greater wear in an engine that will normally operate with an SAE40 lubricant (with similar HTHS viscosities) except at temperatures below around -20C. Around this temperature, the 0w and 5w SAE40 lubricants may show lessor wear rates depending on the warmup cycle, oil and liquid coolant capacity and the engine's technology/metallurgy/application mix

VW & Porsche also used SAE20w-20 viscosity oils as a winter recommendation for many years. I used to use CAT Series 3 HD lubricants in these cases. SAE30 oils had no "w" rating

3 - Mobil 1 15w-50 and Mobil 1 5w-50 are very different "animals" in regards to their overall operating abilities. No 15w-50 oils have been on Porsche's Approval List since around 1999
Mobil 1 5w-50 is the only Porsche Approved SAE50 lubricant - sadly it is not marketed in NA

4 - Felix - For a 15w lubricant (SAE40, 50) it is generally accepted that -20C is the lowest temperature that will enable sufficient cranking speeds, flow and etc. Porsche recommends a 5w-40 oil above -25C and a 0w-40 oil for engines operating below -25C

5 - No lubricant of any brand meeting similar specifications to others has been proven to reduce wear over the others. The same applies to the Boutique oils such as Redline, Motul, Repsol, Amsoil and etc. There are over 100 Approved oils on Porsche's List

6 - Generally, lubricants that meet the ACEA A3/B3 or A3/B3(B4) quality standards are best for use in Euro engines

I hope this is of some interest

JasonAndreas

The normally aspirated 964 and 993 were delivered from the factory with 0w-40 and 5w-40. What weight of oil were the turbo models delivered with?

Kevin

Doug I have seen the piston scuffing with my own eyes on a 993TT engine that was serviced with 0w-40 factory fill at the dealership.. Do what you want with your water pumpers, but I don't recommend it with the air-cooled turbo engines.

md11plt

Kevin,

Is it the startup temp outside or is it the startup temp of the oil in the engine? IOW if it is 20F outside but 35F in my garage, I use an appropriate oil for 35F (unless I take the car to Walmart and let it sit for three hours while I buy oil). Once the oil is up to temp, does it matter how cold it is outside? Using my scenario, is 15-50 OK to use when it is 20F if I start the car in the garage at 35F?

Tom

Basal Skull

Thanx for the info Doung and your real world experience Kevin

so, if I get this... the second number refers to sae at 100 C viscosity but is different from the High Temperature High Shear test protocol (HTHST) at 150 C, and Porsche's approval is based on the HTHST which we can't determine from the regular viscosity numbers on oil...? or do certain weight oils all have the acceptable 3.5 cst HTHST that Porsche approves?

"5 - No lubricant of any brand meeting similar specifications to others has been proven to reduce wear over the others. "
Doug - I thought there were test to look at that ie. SINTEF, and CRC-L-38 test?


if an oil is good at high temps, at low temps/starting car temps, isn't it better for the oil to have a lower viscosity so that it's not too thick for the oil pump to pump? or does it need to be a certain viscoisty/thicker to "stay' on certain surfaces at startup? regardless of the multigrade viscosity rating, oil always seems thicker when cool and more runny when warm...

I've found copies of the porsche 'approved' oils technical bulletin on the net last night but reading it, I can't be sure if its retroactive to 993tt's or it's just for more newer cars...

in the mean time, I'll go back to the 15w40or50

Kevin

How is your oil pump going to pump oil between the pistons and cylinders at startup?? Yes, I realize that we have large oil squiters. But the accelerated wear happens at startup. The lower viscosity helps bearing life, but our engines do not have bearing wear unless we knock out the rod bearings with a missed shift or over rev. So let leave the bearing wear out of the topic and focus on the other critical components with the air-cooled engine. We should ask the Lycoming and Continental airplane guys what they are using for there air-cooled engines right now, and if anything has changed with there oil formulations.

Again, my concern is your $4,500 set of pistons and liners... Dive into the manuals and spec sheets and compare the piston to cylinder wall spec vs the H20 water pumpers..

Doug Hillary

Hi,
Basal Skull - some answers/opinions;
1 - You are correct, the higher viscosity number of a multigrade oil is measured at 100C and must fit into a narrow viscosity band of the SAE J300 chart.
In the case of SAE40 lubricants there are two HTHS minimums depending on the lubricant's viscosity spread. 0w-40, 5w-40, 10w-40 multigrade lubricants must have a minimum HTHS vis. of 2.9cSt. 15w-40, 20w-40, 25w-40 multigrade and SAE40 monograde lubricants must have a minimum HTHS vis. of 3.7cST

Typical HTHS examples:
M1 15w-50 has 4.1cSt, M1 0w-40 has 3.6cSt and M1 5w.40 Turbo Diesel Truck has 4.1cSt. In general terms, the higher the HTHS vis. the slower the "ramp up" speed of a turbo-charger

It is possible for some SAE50 lubricants to have a lower HTHS vis. than a SAE40 oil!

2 - Porsche's Approval process is initially based on the ACEA's test protocols. The following comments do NOT apply to the VW V6 engined Cayenne - VW Approvals apply to this engine family

Porsche's test for HTHS (150C) is based on ACEA's A3 test No1.1.3 (CEL-36-L-A-90) which is continued for an extended period that covers temporary shearing and "polymer regrouping". Porsche also uses ACEA's A3 viscosity test, No 1.1.2 (CEL-14-A-93) which is conducted at 100C and is again extended in duration. These are tightly controlled Lab. tests

There are a number of other Porsche specific tests covering volatility, foaming tendency and etc. Anti foaming ability is very important in many engines with multi oil pumps and similar technologies

The latest (2/06) Porsche TI 1701 Approval List for all standard production vehicles is retrospective to MY84. This List supercedes all earlier TI's.

3 - The ASTM's CRC-L-38 and now obsolete engine test method was multi faceted but basically "only" covered these points, bearing weight loss, varnish and sludge deposits - engine - and Total Base Number (TBN) & Total Acid Number (TAN) relationship and viscosity change - lubricant

The ACEA's test protocols which commenced in 1996 are extensive and are becoming "Universal". They form the basis for Euro Engine Manufacturer's recommendations

4 - Porsche Engineers obviously believe that a 0w-40 or 5w-40 (and M1 5w-50) viscosities are ideal for their engines in terms of cold start lubrication.
In all engines the idea is to get oil FLOWING to the correct locations and to by pass as little as possible in the warm up process. Significant amounts of oil may be unfiltered until it will flow through the filtration media (differential by-pass effect)

High viscosity oils can be in filtration media by-pass until the oil is near 70C
High viscosity oils can take up to five minutes to flow through the ring pack when hot!

Many people who want to use Mineral engine oils in air cooled Porsche engines get best results from 15w-40 "mixed fleet" Heavy Duty Engine Oils (HDEOs). A number of synthetic 5w-40 HDEOs are also available. These lubricants typically have a HTHS vis. around 4cSt and are very heat tolerant and are of course ideal in high compression turbo-charged engines

In the end an Owner must feel happy with their lubricant choice - it helps longevity if it is the correct one for the engine!

My real world experience with air cooled engines includes a mix of 1cyl, 2cyl, 3cyl, 4cyl (includingV4) and V8cyl engine types

Basal Skull

very interesting infomation, thanx guys
From what your implying kevin I guess the air cooled engines have a larger piston to cylinder gap so a thicker oil is needed to 'stay' there (be available) for start up when cold?
I guess it boils down somewhat to what's available in our local stores. I read somewhere that Porsche uses 0w40 in it's race cars but their emphasis may not be on maximum longevity (if turbos spool faster with thinner oil!).
I'll take my list of Porsche approved oils and spend some quality time staring at the shelves next time I go oil shopping and try to factor all this in... and it's also probably other things like how frequently the oil's changed in relationship to how hard the car's driven etc... It's a personal decision/choice...

Doug Hillary

Basal Skull,
yes M1 0w-40 is used in their race cars and as per their Approval List. In other extremely valuable historic vehicles they use a mineral 20w-50 lubricant that is warmed to 80C before their engines are loaded. Mineral 15w-40 oils are used in some other engines under the Factory's care and protection

If you elect to use other than an Approved lubricant use the ACEA A3/B3 or A3/B3/B4 specification as a baseline (along with the correct viscosity). The anti wear characteristics (especially valve train components and at ring/liner interface) of these lubricants are the same as they were 11 years ago

Regards