oil viscosity?

[arjunior45]

what does the oil viscosity means at high temperatures {for example at 100 degrees C}?
Does it means that 'the higher the number the thicker the oil'?
For example an oil with viscosity '23' at 100 degrees C {like Selenia Racing 10W-60} is it thiner than an oil with '24,5' at 100 degrees C {like Castrol Edge 10W-60}?

Or is exactly the opposite?

[AlfaJack]

I thought any 60 was the same viscosity at 100c but have a look here for more info:

http://www.opieoils.co.uk/pdfs/Viscosity-Expalanation.doc

Loads more:
http://www.opieoils.co.uk/technicalinfo.aspx#oilspec

[arjunior45]

Thanks for the links AlfaJack.

No, not all the '60' have the same 'viscosity' at 100 degrees. From those oils I can find here in Greece,
a} Selenia Racing 10W-60 has '23'
b} Agip Racing 10W-60 has '23,5'
c} Castrol Edge 10W-60 has '24,2'
{note : Castrol Edge Sport 10W-60 has just '22,9'}.
and
d} Motul 300V 20W-60 has '22,9'

In conclusion, from what I can see in these links, it is correct that the higher the 'viscosity' number at high temps the thicker the oil is.

Probably it would have been more interesting to know the 'viscosity' at 85 - 90 degrees but did not find anything so far.

At 40 degrees, the numbers are :
a} Selenia : ????
b} Agip : 160
c}Castrol : 161 {sport : 157}
and
d} Motul : 170

[AlfaJack]

If you email Opie Oils I am sure they will give you all the info you need. They post on all of the UK car forums I visit. I think they will post here one day too.

[oilman]

As my names been mentioned, I'd be happy to help with any oil advice or questions if required.

Cheers
Guy
Opie Oils

[AlfaJack]

Hi Guy.
Welcome. Perhaps maybe if we could have your own recommendation and experience on the type of oil for our engines (2.0 16v Turbo - Lancia engines. Same as that in the Fiat Coupe and Lancia Integrales.

Cheers,
Jack

[arjunior45]

As my names been mentioned, I'd be happy to help with any oil advice or questions if required.

Cheers
Guy
Opie Oils

thanks for your reply Guy and wellcome to this forum.

Do you know the viscosity of Selenia Racing {10W-60} at 40 degrees C?

Is there a math formula {or any formula} that connect oil pressure with viscosity?

Regards

Nick

[oilman]

Hi Guy.
Welcome. Perhaps maybe if we could have your own recommendation and experience on the type of oil for our engines (2.0 16v Turbo - Lancia engines. Same as that in the Fiat Coupe and Lancia Integrales.

Cheers,
Jack

Jack

You will see 10w-60 bounded around a lot with reference to Alfas and Lancias although in many cases incorrectly. We use a database for standard road recommendations (unmodified cars used on the road) and many of these cars are in fact 10w-40 or 5w-40 with 10w-60 for "spirited" driving whatever that may mean.

For reference purposes, our database here is a good source of information with accurate recommendations

http://www.opieoils.co.uk/c-851-oils-for-my-car.aspx

Obviously, if you have modified or use your car on track we may recommend a different viscosity or even better quality as a good decision but am happy to help where I can either via my website, PM or via the Forum.

Cheers
Guy

[oilman]

thanks for your reply Guy and wellcome to this forum.

Do you know the viscosity of Selenia Racing {10W-60} at 40 degrees C?

Is there a math formula {or any formula} that connect oil pressure with viscosity?

Regards

Nick

Nick, I have a table that shows the viscosity of oils at various temperatures but it's on XL so you'll need to mail me for this. Basically what I can tell you is at 100degC a 10w-60 (SAE60) will be 24cst (centistokes) and a 10w-40 (SAE40) will be 14cst so the 10w-60 is in fact 70% thicker so this will obviously create higher oil pressure.

All I would say is that oil pressure is a measure of resistance not flow and flow is equally important in lubrication terms.

If you don't need 10w-60 (ie it's not recommended), don't use it as the friction caused by the viscosity (thickness) can:-

Lower BHP
Increase Fuel Consumption
Increase heat in the engine
Increase wear

Cheers
Guy

[AlfaJack]

Nick, I have a table that shows the viscosity of oils at various temperatures but it's on XL so you'll need to mail me for this

I have just added xls formats to the attachment options if you want to try it.

[arjunior45]

Nick, I have a table that shows the viscosity of oils at various temperatures but it's on XL so you'll need to mail me for this. Basically what I can tell you is at 100degC a 10w-60 (SAE60) will be 24cst (centistokes) and a 10w-40 (SAE40) will be 14cst so the 10w-60 is in fact 70% thicker so this will obviously create higher oil pressure.

All I would say is that oil pressure is a measure of resistance not flow and flow is equally important in lubrication terms.

If you don't need 10w-60 (ie it's not recommended), don't use it as the friction caused by the viscosity (thickness) can:-

Lower BHP
Increase Fuel Consumption
Increase heat in the engine
Increase wear

Cheers
Guy

Dear Guy,

thanks for the answer and I do understand your meaning about oil flow and pressure-resistance.

Viscosity seams to me like 'density' and I was wandering if the difference in viscosity at various oil temperatures {more in the range from 60 degrees C to 105 degrees C} can influence the oil pressure that much to have a difference of almost 4 bars in oil pressure at idle.

You see, my oil pressure gauge {the oem one} was indicating almost 0 bar at 105 degrees {4 bars at 60 degrees C} and without oil pressure it is obvious to me that there is not oil flow too! Am I correct?

Any way, there was a faulty 'oil pressure bulb - sender', indicating - 1,5 bar in the hole arc of 0 - 8 bar. I replace the 'bulb - sender' and test the oil pressure {as indication of oil flow} with a very accurate analog pressure meter and now I have + 1,5 bar / 95 degrees C at idle - with the analog pressure meter and the 'new' oil pressure sender too.

But in any case, it will be nice to know if viscosity can influence that much {and how much} the oil flow and oil pressure.

Regards

Nick

[oilman]

As the temp rises the oil thins (hopefully the attachment here will work) the oil pressure will reduce as the oil thins.

Cheers
Guy