Porsche Enthusiasts Club Forum

Can I use VW Quantum Platinum oil 5w/40 as I can get it cheap ?
Car is 2.7 944. Is it suitable ? Car has a history of fully synthetic oil.

Hi

I would have thought that oil was a little thin to say the least....

Umm I just looked that up...are you sure its not just a SEMI synthetic ?

It seems much too cheap to be a FULL synthetic...

I use 15/50 (Fuchs) as an example in my 928...

All the best Brett

It is a fully synth, the details are here:-
Quantum Platinum is a fully synthetic SAE 5W-40 engine oil for all year round use in applications where an oil of that
viscosity grade and performance level (API SM/CF, ACEA A3/B3/B4/C3) is recommended.

My only issue is that API SM is low in ZDDP which will possibly be an issue in old technology engines with the sort of cam followers that the 944 has. The engine is specs at 10W/40 so the 5W when cold should be OK, you might get more oil leaks though! 40 viscosity at temp will be fine.
Personally I favour a mineral 10/40 changed every 3K or a semi synth changed at 6K, a lot of this will depend how many miles you do a year & whether it uses oil. Track days I might run a full synth, but they weren't designed around it.

Hi,
Thanks for the replies. I was mainly thinking the 5w due to early morning cold starts and that it's sup[posed to be a 'better oil' I want to use it as a frequent driver, but only about 5k a year.

Agree with above, the oil being a bit thin will find any leaks in the engine, but should help the starter on cold starts

I have used fully synth 0w40 and 5w40 in my 1991 S2 and have not noticed any extra leakage or problems so if you get it cheap why not try it and see, depends on age of the engine and wear internally, I would have thoght any oil regardless of viscosity would eventually end up as thin as each other once up to temp.

ok, so Quatum platinum would be ok with a zddp additive ?

Nope the second number e.g. 40 in 5/40 is the viscosity when HOT. So only a x/40 will be a given viscosity, an x/50 would be more viscous.

I agree with the second number issue what I was implying was 0w40 5w40 or 15w40 would end up similar viscosity when hot.
See below shamelessly copied from PCGB article

Oil viscosity ?This is a common misconception.

It leads to comments like:

"You must not use 5w oils"

"5w oils are too thin"

"Use 10w-40 but not 5w-40"

Some facts need to be straightened out here and hopefully I can do this without losing those that are interested.

So what is the difference between a 5w-40 and a 10w-40 @100degC?

Basically NONE!

SAE determines the viscosity (+/-) that the oil needs to be at 100 degC and these need to be met in tests to give the oil it's API rating (xw-xx or xxw-xx).

They are as follows: (within a margin)

SAE 30 = 11.00cst
SAE 40 = 14.00cst
SAE 50 = 18.50cst
SAE 60 = 24.00cst

Compare these SAE 40 oils at 100degC (0w, 5w, 10w, 15w)

Motul 300V 5w-40.................Viscosity = 13.80cst Motul 300V 10w-40................Viscosity = 14.00cst
Silkolene PRO S 5w-40............Viscosity = 14.89cst
Motul 8100 X-cess 5w-40........Viscosity = 14.00cst
Fuchs Titan Supersyn 5w-40....Viscosity = 13.60cst
Castrol Performance 10w-40.....Viscosity = 14.50cst
Silkolene XTR 10w-40 (semi).....Viscosity = 14.70cst
Mobil 1 0w-40........................Viscosity = 14.30cst
Motul 8100 0w-40...................Viscosity = 13.30cst
Silkolene Turbolene D 15w-40....Viscosity = 14.40cst
Total Quartz 15w-40...............Viscosity = 14.50cst

These figures are not by chance and include synthetics, semi-synthetics and mineral oils they are all in the range to be labelled a Xw or XXw-40 multigrade oil.

So, what's the "W" number all about then?

It stands for "winter" not "weight" as often confused and called on many U.S. articles on oil!

This number is the "cold crank" viscosity and nothing to do with the oil viscosity when the engine is up to temperture. These numbers are related to the oils ability to operate in cold temperatures. 0w oils were originally designed to operate in arctic climates that's why they operate at ferrous monkey endangering temperatures of -35degC and below!

The benefits of the lower viscosity oils (0w and 5w) is that they flow more easily and quickly when cold and therefore protect the engine better on cold start when 80% of the engine wear occurs.

So, yes it's true an sae 40 is an sae 40 when hot whether its a 0w, 5w, 10w, 15w or whatever and that's a fact. The same goes for 20's, 30's, 50's, 60's and so on.

maybe i'll jst go with at 10w/40 semi. like Quantum synta...