oil - question for GC

Currently reading:
oil - question for GC

all standard sierra cosworths seem to like duckhams.:)
most cosworth specialist do not recommend synthectics. the engines don't like it. why this is, i don't know. must be standard tolerances i guess.:)
 
It has absolutely nothing to do with tolerances.

Synthetic is a type of basestock, not the viscosity (thickess) of the oil.

Cheers
Simon
 
oilman said:
It is a highly modded one under a lot of stress. A mineral oil would carbonise in minutes!

Cheers
Simon

I have no problem with this statement. I just have a problenm to compare two different animals.

I work on the other side of the industries and do not only Fiat tuning. I do research in the field too. And by changing the alloy alone you will meet totally different requirements in terms of material, consistency and tolerance factors, which have even more effects in turn including the oil.

From research I have at least learned one thing, that you can only draw conclusions when the individual conditions are quantifiable. Everyone who loves maths more than me can easily calculate how wrong we can be with our conclusion, when more than on variable has to be considered in a string of events (technically, chemically and mathematically).

This is why people all over the world tried to set out norms and to eliminate any uncertainty possible. And this is what I base my work on.

For many people it might not be relevant but so far successful heading this bit of advice I took from people more clever than me.
 
oilman said:
It has absolutely nothing to do with tolerances.

Synthetic is a type of basestock, not the viscosity (thickess) of the oil.

Cheers
Simon
so why do standard cosworths not like synthectic oil?:)
 
There are plenty of standard cosworths running on synthetic and semi-synthetic oil without problems so please tell me why they don't like it.

As far as I know there are no issues other than perhaps the use of a 0w-40 where a 15w-50 is specified.

Cheers
Simon
 
We are talking Cosworths and that's what I am referring to.

Cheers
Simon
 
fixitagaintomorrow said:
Would the same apply for a Fiat Coupe 20vt?

No because the standard viscosity is 10w-40, so a 5-40 would be fine ( a bit smokey if your seals were on the way out) whereas the tipo was 15-40 IIRC so 5-40 would be too thin. However give Oilman credit, He can't know every car's standard viscosity off the top of his head.
 
It depends what you call too thin.

We recommend 5w-40 for stock road coupes but mant are modded and in these cases we recommend 10w-50 to better cope with heat.

Cheers
Simon
 
oilman said:
It depends what you call too thin.

We recommend 5w-40 for stock road coupes but mant are modded and in these cases we recommend 10w-50 to better cope with heat.

Cheers
Simon
you must be the only one then who recommends such a thin oil. 15/40 is a much better oil for the coupe.
as regards cosworths, synthectics are not recommended for this engine. this is not me saying it, but specialists who service and rebuild cosworths for a living.
infact CCC magazine[god rest its sole], ran several issues with regards to cosworths engine building, maintenance and getting the most from an engine and rolling road shootouts. they printed it there not to use synthectics.:)
 
I think there are some misconceptions here.

What is thin about a 5w-40?

Compare these numbers:

Grade...........................................5w-40......................15w-40

Viscosity (thickness at 0degC)..........800cst......................1300cst
Viscosity (thickness at 100degC).......14cst........................14cst

They are both the same at 100degC (because they are both rated as sae 40's) and the 5w-40 is about 40 times thicker at 0degC than the 15w-40 at 100degC so how can it be too thin?

The "w" number is it's cold crank viscosity and these are rated differently to the second number. It's about the oils ability to flow at low temps.

Cheers
Simon
 
Last edited:
oilman said:
I think there are some misconceptions here.

What is thin about a 5w-40?

Compare these numbers:

Grade...........................................5w-40......................15w-40

Viscosity (thickness at 0degC)..........800cst......................1300cst
Viscosity (thickness at 100degC).......14cst........................14cst

They are both the same at 100degC (because they are both rated as sae 40's) and the 5w-40 is about 40 times thicker than the 15w-40 at 100degC so how can it be too thin?

The "w" number is it's cold crank viscosity and these are rated differently to the second number. It's about the oils ability to flow at low temps.

Cheers
Simon

You mean 0'c? ;)
 
Thanks for the useful info Oilman!

Regards,

GC

BTW - guys - you - we - are very lucky to have an oil expert like Oilman on board.
 
oilman said:
I think there are some misconceptions here.

What is thin about a 5w-40?

Compare these numbers:

Grade...........................................5w-40......................15w-40

Viscosity (thickness at 0degC)..........800cst......................1300cst
Viscosity (thickness at 100degC).......14cst........................14cst

They are both the same at 100degC (because they are both rated as sae 40's) and the 5w-40 is about 40 times thicker at 0degC than the 15w-40 at 100degC so how can it be too thin?

The "w" number is it's cold crank viscosity and these are rated differently to the second number. It's about the oils ability to flow at low temps.

Cheers
Simon
the 5/40 is a thinner oil in winter spec, yes?
so for me, its too thin for all round protection. this is why 90% of coupe forums/owners go for 15/40.
please tell me why a 15/40 is not suitable? :)
 
I didn't say it wasn't suitable, it's an sae 40 as is a 5w-40, 10w-40 etc and therefore has the same viscosity at higher temps.

Why is 5w too thin as you see it? If 14cst is enough viscosity for the car, why is 800cst too thin, as I don't see your logic.

Cheers
Simon
 
oilman said:
I didn't say it wasn't suitable, it's an sae 40 as is a 5w-40, 10w-40 etc and therefore has the same viscosity at higher temps.

Why is 5w too thin as you see it? If 14cst is enough viscosity for the car, why is 800cst too thin, as I don't see your logic.

Cheers
Simon
what about very cold temps[well below freezing]? thats where the 15/40 works, and is good at high temp. the operating range of the 5/40 is too narrow. there is no real advantage using it over a 15/40.:)
 
Back
Top