oil viscosity

[Limbo]

ok i've always been told that reading oil viscosity the first is at low temp & the other is at high temp.

Now recently talking to a mechanic he pulled out an oil viscosity book which showed that the low temp affect the higher temp viscosity.

Let me explain
a 5w40, the 40 is actually a lower viscosity than say a 10w40.
so the top heat range is actually higher on the 10w40

I've been trying to look around the net to explain if this is the case.

I've come across Nulon's website and they have the 5w40 & 10w40, both synthetic, but the 10w40 has a higher viscosity at 100degrees.
(Have alook for yourself under the specifications, I only picked Nulon cos it had more info on oils and these were both in the same category of oils)
http://www.nulon.com.au/products/Full_Synthetic_5W-40_Long_Life_Petrol_and_Diesel_Engine_Oil/

http://www.nulon.com.au/products/Full_Synthetic_10W-40_Hi-Tech_Fast_Flowing_Engine_Oil/


Just something i found and wanted to confirm further. Anyone else heard of this?

Reason i ask this is cos honda recommends 10w30. Everyone always says 5w30 is better, but i've noticed buring in 5w30 when i used it and always wondered why until i spoke with my mechanic.

can anyone shed any light on the matter or has wat i've previously been told a myth? i.e they are the same at high temp....

so far the info that i've found seems to say differently. Just want some thoughts on the matter.:thumbsup:

[Limbo]

ok further reading (what happens when your on holidays)

http://www.maintenanceworld.com/Articles/thibault/HowToRead.htm

Apparently the W has a range for i.e the 40, thus seems to make sense that there is a difference, and also that i heard that the 0w40 is at the lower end of the 40 weights.

must be why honda has 10w30, higher 30 wieght viscosity to reduce burn


Have a look at the website below (formatting in ozhonda is abit crappy)
SAE Viscosity Grade

Viscosity (cP) at Tempertature (°C)

MaxBorderline Pumping Temperature (°C)
Viscosity at 100°C Min----- Max

0W 3250 @ -30 -35 3.8

5W 3500 @ -25 -30 3.8

10W 3500 @ -20 -25 4.1
15W 3500 @ -15 -20 5.6
20W 4500 @ -10 -15 5.6
25W 6000 @ -5 -10 9.3
20 5.6<9.3
30 9.3<12.5
40 12.5<16.3
50 16.3<21.9
http://www.wearcheckusa.com/literature/techdoc/WZA007.htm#pg2

[Limbo]

ok so from what i've learnt is that only difference in the 0w compared to thw 5w is it can go to -35degree (not where i'm gonna be at)

and viscosity at 5w compared to 10w is only .3 & 5 degrees, the

5w is at -30 degrees with viscosity of 3.8
10w is at -25 degree with viscosity of 4.1

pretty sure it never gets as low as -25degrees where i live
i'm going with a 10w40 next change it looks like (but that's due to me wanting higher top viscosity for track).

Hope this thread helps others looking at which oils viscosity they want.

[aaronng]

ok so from what i've learnt is that only difference in the 0w compared to thw 5w is it can go to -35degree (not where i'm gonna be at)

and viscosity at 5w compared to 10w is only .3 & 5 degrees, the

5w is at -30 degrees with viscosity of 3.8
10w is at -25 degree with viscosity of 4.1

pretty sure it never gets as low as -25degrees where i live
i'm going with a 10w40 next change it looks like (but that's due to me wanting higher top viscosity for track).

Hope this thread helps others looking at which oils viscosity they want.

For the same reason that you explained, I wouldn't hesitate to use a 0w-40 or a 5w-40 if I find one that is better than the 10w-40.