5w30 vs 0w40 Trying to get my head around KV

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156
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New Zealand
I recently swapped oils in my car, I had been running Castrol Edge 5w30 for the past two years. Last service I decided I try the Edge 0w40. Now looking at their KV ratings the 5w30 is 71.4 @40° & 12 @ 100°c. The 0w40 is 77.5 @40° & 13.1 @100°c. Based on this the 5w30 should flow better when cold right? But in the real world I find the 0w40 flows much better as I no longer have tappet noise on start up but could feel the 5w30 was better when warm (Hence I want to try 0w30 next). Now there must be more to KV ratings than meets the eye. I've read the Motor oil uni article which was great but it doesn't really delve into KV ratings as such. Who can explain this better for me? Thanks
 
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1,271
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Dallas Texas
Originally Posted By: SXE10
I recently swapped oils in my car, I had been running Castrol Edge 5w30 for the past two years. Last service I decided I try the Edge 0w40. Now looking at their KV ratings the 5w30 is 71.4 @40° & 12 @ 100°c. The 0w40 is 77.5 @40° & 13.1 @100°c. Based on this the 5w30 should flow better when cold right? But in the real world I find the 0w40 flows much better as I no longer have tappet noise on start up but could feel the 5w30 was better when warm (Hence I want to try 0w30 next). Now there must be more to KV ratings than meets the eye. I've read the Motor oil uni article which was great but it doesn't really delve into KV ratings as such. Who can explain this better for me? Thanks
Try 0W-30 Edge and you may have the best of both worlds! smile Your 0W number is indicating better resistance to flow, as in not as much. The 5W may in fact have been great, but the 0W trumps it. The KV was less in the 30 so your engine did not have to use as much energy to spin it. People that put 20-weight oil in their cars (i am starting to become a believer, slowly but surely) have more power. Even read an article about a guy with a Civic hybrid from 2007 that put in two or three quarts 0W-10 oil and the rest 0W-20.. and it was amazing. Your KV is not correlating to the 0W number, no direct connection. Frequently you can have a 0W oil with higher KV whereas you would think it would be THNINNER at temp due to the 0W. The W number and the second nnumber have no real relation. Its all about how the oil is made, and who makes it. smile
 
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The Edge 0W-40 has a viscosity of 5800 cP @ -35 degrees C, this would be compared to a 5W-x @ -30 degrees C (note different testing temperatures for 0W vs. 5W). The U.S. Edge with Syntec 5W-x's have a viscosity of 6600 cP @ -30 degrees C. (Hope this is helpful).
 

SXE10

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156
Location
New Zealand
Originally Posted By: 45ACP
Try 0W-30 Edge and you may have the best of both worlds!
You can't buy it here unfortunately. The only 0w30 I can find is Motul. Oil is still pretty misunderstood downunder. People still put 20w50 in modern engines & think 10w40 is top of the line frown So the KV has no relevance to the viscosity rating then. What are the important things to look at when reading the data sheets? What do these cP values mean?
 
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8,051
Location
Michigan
Originally Posted By: SXE10
Originally Posted By: 45ACP
Try 0W-30 Edge and you may have the best of both worlds!
You can't buy it here unfortunately. The only 0w30 I can find is Motul. Oil is still pretty misunderstood downunder. People still put 20w50 in modern engines & think 10w40 is top of the line frown So the KV has no relevance to the viscosity rating then. What are the important things to look at when reading the data sheets? What do these cP values mean?
The kinematic viscosity values are very relevant to the viscosity rating. The SAE system of viscosity grades is based on kinematic viscosity (units are centistokes, or cSt) at 100C. SAE viscosity grades are: 20: 5.6-9.3 cSt 30: 9.3-12.5 40: 12.5-16.1 The other measure of viscosity is dynamic (also known as absolute) viscosity. Its unit is the centipoise (cP). In the API oil specifications, the High Temperature, High-Shear (HTHS) viscosity is a measure of dynamic viscosity at 150C while the oil is being sheared in an apparatus that simulates a bearing. This is a measure of how well an oil protects at extreme conditions. HTHS viscosity is also used to classify an oil's viscosity grade. 20-weights must have a miminum HTHS of 2.6cP, 30's must have 2.9, 40's must have 3.5.
 
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Messages
1,271
Location
Dallas Texas
Originally Posted By: SXE10
Originally Posted By: 45ACP
Try 0W-30 Edge and you may have the best of both worlds!
You can't buy it here unfortunately. The only 0w30 I can find is Motul. Oil is still pretty misunderstood downunder. People still put 20w50 in modern engines & think 10w40 is top of the line frown So the KV has no relevance to the viscosity rating then. What are the important things to look at when reading the data sheets? What do these cP values mean?
Its like that here too. And the amazing thing is that if you did put 20W-50 OR 10W-40 in a modern engine it would run still... shrug
 

SXE10

Thread starter
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156
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New Zealand
Yeah a modern engine will still run on 20w50 but things like VVTi & VTEC don't seem to like it much. My never ending search for 0w30 continues... What are peoples thoughts on Motul H-tech 100 plus 5w30? It's quiet reasonably priced here. Thanks A_Harman for your explanation. I have much to learn.
 
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10,146
Location
Burlington, Ontario, Canada
Originally Posted By: SXE10
I recently swapped oils in my car, I had been running Castrol Edge 5w30 for the past two years. Last service I decided I try the Edge 0w40. Now looking at their KV ratings the 5w30 is 71.4 @40° & 12 @ 100°c. The 0w40 is 77.5 @40° & 13.1 @100°c. Based on this the 5w30 should flow better when cold right? But in the real world I find the 0w40 flows much better as I no longer have tappet noise on start up but could feel the 5w30 was better when warm (Hence I want to try 0w30 next). Now there must be more to KV ratings than meets the eye. I've read the Motor oil uni article which was great but it doesn't really delve into KV ratings as such. Who can explain this better for me? Thanks
You haven't said at what cold start temp's your making your comparison? Also we don't know the HTHS viscosity of each oil so it's rather hard to accurately compare the two oils. The reason is that HTHSV trumps the KV100 spec'. The two oils do have different chemistries and I suspect the 5W-30 has less VIIs and therefore it's HTHSV may be very close to that of the 0W-40; their KV100 spec's afterall aren't that far apart. That being the case, in conjunction with the lower VI of the 5W-30, it doesn't surprise me that the Edge 0W-40 may be lighter on start-up at non extreme cold temp's.
 

SXE10

Thread starter
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156
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New Zealand
Coldest it gets here is about 4°C (40°F) on a cold winters morning. I failed to find any reasonably priced 0w30 over here so I'm going to try Motul 8100 X-Clean 5w30. Getting it cheap through a mate who knows the importer. Also got some H-Tech 100+ 5w30 to try in the Mrs Corolla. Bit of an overkill but it's cheaper than buying a 10w40 blend at retail. Anyone here had experiences with either of these oils?
 
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10,146
Location
Burlington, Ontario, Canada
The viscosity of the Motul 8100 X-Clean 5W-30 is very similar to the Edge 5W-30. Can't comment on the Motul High Tech 5W-30 as it's not sold hear, do you have the link for that oil? Of course any of the oils discussed hear are far superior to a 10W-40 blend.
 

SXE10

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Messages
156
Location
New Zealand
Originally Posted By: CATERHAM
The viscosity of the Motul 8100 X-Clean 5W-30 is very similar to the Edge 5W-30. Can't comment on the Motul High Tech 5W-30 as it's not sold hear, do you have the link for that oil?
Can't find anything on the Motul site for the H-Tech. It's about $1 per L cheaper than the 8100 so make of that what you will. Crazy idea but could I do a 50/50 mix of Edge 0w40 & 5w30? Would that accomplish anything. I see some guys on here mixing grades. Still got about 7K km til my next service so will be a while til I can comment on any difference I noticed between Edge 5w30 & the Motul. Especially interested to see if my tappet noise comes back on start up.
 
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