Doug Hillary

Hi Matt,
the world of Tribolgy is changing rapidly with both mineral oil basestocks and those forming the basis for hydrocracked Group 3 synthetics taking giant leaps forward
Some Group 3 oils like certain Shell, Havoline and Castrol products probably outperform some other better known "fully synthetic" products.
ExxonMobil makes a great range of basestocks for Group 3 production - they are the largest supplier

I have a great respect for Shell's Rotella "T" - it is not available in OZ. I once worked for Caltex-Chevron many years ago and know that they make excellent lubricants

Group 5 oils (Motul, Delavc 1, some Castrol products and etc) are still at the top of the pecking order in lubricant performance. M1 is Group4/5 and their 15w-50 (5w-50 in OZ) is a worldwide best seller no doubt on its performance over many years

Regards
Doug

Dennis Wilson

Doug,

Thanks for your response. It's the carbon in suspension that can cause coking on shutdown of turbocharged engines. This is a very common problem with the 931 and many others. Letting it idle for a few minutes before shutdown helps reduce this problem but with the heat it still will occur. Would you recommend a different oil to reduce the coking or is this going to be a function of the filter?

Dennis

Doug Hillary

Hi,
Dennis - modern synthetic oils are not prone to the coking problems usually attributable to mineral oils of the past (during the 1970s-80s)

The correct viscosity however is important in cooling turbochargers and a thicker oil is not better oil! Mineral oils above xxw-40 do not flow very well - even when hot - and this is one reason for Porsche and others moving to factory fill with a synthtic oil in 1992

The only Porsche Approved SAE "50" (5w/15w-50) oil is Mobil 1. Porsche recommend a minimum of a Group 3 synthetic 0w/5w-40 oil for all vehicles back to 1973 and only officially Approve such viscosity oils

This is one thing that makes using HDEOs a positive option as these lubricants are designed to live very well indeed in turbocharger bearings, fire belt(upper piston) and ring pack areas etc. They are especially suited to high compression pressures and component loading and will operate at up to 4.5% soot loading (synthetics)

The filter if changed as recomended will have no effect on the coking issue which was/is primarily caused by oxidation(burning) and older specification mineral oils are especially prone to this above about 125C

This is but one reason why Porsche have always required oils with a dual petrol/diesel rating (say SL/CF or ACEA A3/B3) and at one stage their factory fill in air cooled engines was Shell Rimula/Rotella - a mixed fleet diesel oil

Regards
Doug

Dennis Wilson

Doug,

Could you give some brand names and type for the group 3 and 5 oils? Castrol Syntech? Mobil 5000, 7500, 1? Amsoil? etc?

As always, your expertise is appreciated.

BTW one of the used turbo's I scavaged for my rebuild was coked until the inlet and outlet reserviors were filled. Good thing I only need the exhaust housing from it. Love that dino oil.

Dennis

Doug Hillary

Hi Dennis,
it is difficult for me to give you details of oils sold in the US but these in a general sense may be of some help;

Castrol Syntec - Group 3
Shell Helix Ultra synthetics - Group 3
Havoline synthetics - Group 3
Valvoline synthetics - Group 3
Amsoil - Group 3/4 (some Grp 5)
Motul - as for Amsoil
Mobil 1 - Group 4/5 (M1 T&SUV 5w-40 is Grp 5)
Delvac 1 - Group 5
Esso XD 3 (as for Delvac 1)

Most mineral oils are Group 2, semi-synthetics and the cheaper "full synthetic" oils are most likely to be Group 3, the more expensive synthetic oils are likely to be Group 4 and the most expensive Group 5. Usually you get what you pay for - the best is more expensive!

The six oil "Groups" are;
Group 1 - Solvent freezing
Group 2 - Hydroprocessing and refining
Group 3 - As for Group 2 but to a much higher level of refining
Group 4 - Chemical reactions (usually Polyalphaolefins (PAOs))
Group 5 - Created - Esters and Polyolesters are common
Group 6 - New - Very advanced chemistry

The new refining developments centering on Group 3 base oils is now bearing fruit in that many semi-synthetics and Group 3 "full synthetics" offer benefits at lower prices than Group 4 and 5 oils

There is no conclusive evidence that any oil or brand (synthetic or mineral) of similar specification will make an engine last longer than another

Synthetic lubricants offer some user advantages at the extremes and in newer more sophisticated engines they may be the only real operational choice

Regards

FlyingDog

Doug, thank you for sharing your wealth of oil knowledge.

Doug Hillary

Matt,

thanks - and my pleasure
I love the Jeep! They are quite popular here too against all the robust Japanese & Korean competition

Regards

TeufelHei

After reading as much as I could on the various oils currently produced and generally available, and also Dougs extremely informative input, I changed brands and went for Castrol Syntec 5w-50.

According to their website, Syntec Base is made by select refinement and chemical treatment. Would this put it in the Group 4 Catagory?

I almost got a bunch of Mobil 1 5w-40 SUV/Truck, but the demon in my head said "what about detonation?" Is it's status as a Polyoleoester rather than natural hydrocarbon base the reason it is less "consumable" to our engines?

Doug Hillary

Hi Tim,
Castrol's Syntec 5w-50 is a Group 3 lubricant with a good reputation but does not have Porsche Approval (this includes passing special test protocols including anti-foaming - foaming may lead to detonation), their 5w-40 grade has. As mentioned earlier the only Porsche Approved ??w-50 oil is M1

Yes Tim, Delvac 1 5w-40 (and M1 5w-40 T&SUV) has a base structure and additive package that tends to reduce oil consumption in many engine families. It is also a very robust SAE40 grade oil (some SAE50 oils are almost SAE40 grade and vice-versa) and is especially designed to resist oxidation and foaming (like all HDEOs) so will not readily lead to detonation
As mentioned earlier all "mixed fleet" HDEOs - both mineral and synthetic and with a quality rating beyond CH-4/SJ - are especially designed to resist piston and ring land deposits and oxidation

Tim the oil you purchased will perform well in your car - I presume that it has A3/B3 on the label?

Regards

TeufelHei

Doug,

Yes the ACEA: A3/B3 is present on the label. Also, Castrol claims to have Porsche approval for this oil on the label as well as recommending it (and their 5w-40) as correct oils for our cars via their website.


Castrol Label: "Also meets engine protections requirements of ILSAC GF-3, Porsche, BMW, Volvo, and Mercedes Benz."

You made mention of a type of "litmus" paper test for oil samples. Where would one get such an item? What can it test for specificaly?

Doug Hillary

Hi Tim,
sadly the Marketing Depts take license on the wording and these words are typical;

"Castrol Label: "Also meets engine protections requirements of ILSAC GF-3, Porsche, BMW, Volvo, and Mercedes Benz."

The oil is not Porsche Approved (as at 5/8/2005). The indicated ACEA A3/B3 quality testing is however a great starting point as the oil will have a HTHS viscosity around/above Porsche's minimum.
This is why the likes of 10w-30 oils are not suitable for use in a 928

Some oils Companies like Amsoil will not pay the fees required to have their products (some) Tested or Certified. This does not mean that the product is inferior

The "blotter test" is very basic and very good and can become a practiced part of engine maintenance as with experience it will show;
a) viscosity position (when compared to new)
b) level of certain combustion contaminants
c) fuel dilution (related to a) above)

This link to a Commercial product which I do not use or endorse may assist you;
www.gwrauto.com/One%20Drop.htm

I use a simple blotter as I have done since the late 1950s

Regards