Motor oil grades and what they exactly mean
10-23-2003, 02:35 PM
#1
Thread Starter
Motor oil grades and what they exactly mean
I know the S2000 manual says that 10W-30 is recommended for our cars. Correct me if I'm wrong but doesn't the first set of numbers dictate how well the oil will do in the cold and the second set (after the hyphen) is a measure of how well the oil holds up in the heat, right? OK, maybe I don't have enough knowledge and the full picture of how oil grade numbers work but won't putting the 5W-30 in our cars only help? It may not help (unless you're in Siberia), but according to what I know, I don't see how it would hurt. I read in some post how since 5W is thinner it won't hold up as well under extreme heat (high rpm driving) but I thought that is solely based on the second set of numbers. Following that logic, what stops us from putting like 0W-60 in our cars? Maybe it's the cost, I dunno. Can someone shed some light on this? Thanks.
10-23-2003, 03:49 PM
#2
Registered User
There has to be a distinction made here foirst between mineral-based oil, and synthetic oil. As you correctly state, the 10w in a 10w30 represents the oil's performance at cold temperatures. That si the same for mineral and synoil.
Let's answer your questions first from the mineral oil side. For simplicity, let's just take 10w30 as the baseline.
Mineral oil will be made from a 10w stock - in order for the oil to perform as a 30w when it is hot, additives called viscosity index (VI) additives are blended in. These are actually polymers, or plastics. They have the unique prorperties of aligning themselves differently as temperatures change. So they effectively raise the vis of the oil to 30, which means the oil will thin at the same rate as a straight 30 weight oil would at the same temp (100degC). A 5w30 will essentially be a 5w stock with more VI added. I suppose you could use a 0 weight and add a ton of VI improver, but that is not practical, as we shall see.
Now, a 10w30 is useful and safe down to about 0 degF. if your car is garaged, or it never goes at or below zero frequently, then 10w30 is what you want.
The case against 5w30 when 10w30 will suffice is that VI improvers are not 100% stable, and not 100% recoverable. Over time, they will lose their capacity to act right, through a process known as shear. VI's have gotten much better over the years, but they are not shear stable completely, esp. in a high revving engine. As they shear, the oil starts to revert back to its base stock spec - so the 30 weight could be a 22w or lower. Then, the protective quality of the oil starts to become a concern. Even though mineral oils tend to thicken through oxidation, having the oil too thin from the breakdown of the VI improvers is not good. I have never seen a 0w30 mineral oil, and the reason is the high amount of VI that would be needed, and the inherent instability of the vis rating,
Now for a synoil, they are engineered molecule by molecule, and certain propertiues can be designed into them, They are naturally high in viscosity range, detergency, and generally require little or no VI improvers. A 10w30 synoil usually has none, a 5w30 synoil perhaps a little. 0w30 synoils may or may not have more. Since they do not have VI improvers, the issue of shear stability is essentially out of the equation. They will retain their vis ratings at high and low temperatures. The base stocks do not have to be real low, since they lack the waxes crystals which cause mineral oils to thicken so much at very cold temperatures.
A 10w30 synoil is good for temps well below zero - it has excellent pumpability even at -20degF. A 5w30 synoil will flow faster at cold temps, and a 0w30 even faster - perfect for Siberia, or for a one grade year round choice.
I tend to use oils that I have analyzed for their base stocks and additives. Some of the best are Amsoil Series 2000 in 0w30, its "regular" synoil at 10w30, and the Red Line 5w/10w30 oils. These can be used year round in any climate.
Now, the second question about "why not use a thicker oil and be done with it"?
Asssuming you could make a 0w60 without gobs of VI improver, there are still other lubrication issues relevant:
1) Flow rate; too thick and the oil will not flow fast enough, and cooling of the bottom 1/3 of the engine can be compromised
2) Parasitic drag - too thick an oil will consume horsepower and lower fuel mielage and raise emissions
3) oil pressures can be changed, which can effect even the opening of the oil filter's bypass valve.
While there are 0w60 made (I think castrol R in Europe is one), they are designed for very special applications, and the cars themselves optimized for the recommendation.
Your Honda was spec'd for 10w30 for a reason. In synoil, you can use 5w30 or 0w30 as you choose to. In mineral oil, stick with 10w30 unless you live and drive in a very cold winter climate, where 5w30 may be needed.
So, use a 10w30 mineral above 0degF, or a 10w30 synoil for winter. In extreme cold, use a synoil.
If you race your car, or live in an area of extreme heat, a 5w40 synoil like "European Formula" Mobil1 might be a good choice.
What do i use? I plan to use either Amsoil 10w30 or the Series 2000 0w30 unless I see leaks. I also may use Red Line 10w30. I change once a year, which is only about 4000 miles for me.
I hope this helps.
Let's answer your questions first from the mineral oil side. For simplicity, let's just take 10w30 as the baseline.
Mineral oil will be made from a 10w stock - in order for the oil to perform as a 30w when it is hot, additives called viscosity index (VI) additives are blended in. These are actually polymers, or plastics. They have the unique prorperties of aligning themselves differently as temperatures change. So they effectively raise the vis of the oil to 30, which means the oil will thin at the same rate as a straight 30 weight oil would at the same temp (100degC). A 5w30 will essentially be a 5w stock with more VI added. I suppose you could use a 0 weight and add a ton of VI improver, but that is not practical, as we shall see.
Now, a 10w30 is useful and safe down to about 0 degF. if your car is garaged, or it never goes at or below zero frequently, then 10w30 is what you want.
The case against 5w30 when 10w30 will suffice is that VI improvers are not 100% stable, and not 100% recoverable. Over time, they will lose their capacity to act right, through a process known as shear. VI's have gotten much better over the years, but they are not shear stable completely, esp. in a high revving engine. As they shear, the oil starts to revert back to its base stock spec - so the 30 weight could be a 22w or lower. Then, the protective quality of the oil starts to become a concern. Even though mineral oils tend to thicken through oxidation, having the oil too thin from the breakdown of the VI improvers is not good. I have never seen a 0w30 mineral oil, and the reason is the high amount of VI that would be needed, and the inherent instability of the vis rating,
Now for a synoil, they are engineered molecule by molecule, and certain propertiues can be designed into them, They are naturally high in viscosity range, detergency, and generally require little or no VI improvers. A 10w30 synoil usually has none, a 5w30 synoil perhaps a little. 0w30 synoils may or may not have more. Since they do not have VI improvers, the issue of shear stability is essentially out of the equation. They will retain their vis ratings at high and low temperatures. The base stocks do not have to be real low, since they lack the waxes crystals which cause mineral oils to thicken so much at very cold temperatures.
A 10w30 synoil is good for temps well below zero - it has excellent pumpability even at -20degF. A 5w30 synoil will flow faster at cold temps, and a 0w30 even faster - perfect for Siberia, or for a one grade year round choice.
I tend to use oils that I have analyzed for their base stocks and additives. Some of the best are Amsoil Series 2000 in 0w30, its "regular" synoil at 10w30, and the Red Line 5w/10w30 oils. These can be used year round in any climate.
Now, the second question about "why not use a thicker oil and be done with it"?
Asssuming you could make a 0w60 without gobs of VI improver, there are still other lubrication issues relevant:
1) Flow rate; too thick and the oil will not flow fast enough, and cooling of the bottom 1/3 of the engine can be compromised
2) Parasitic drag - too thick an oil will consume horsepower and lower fuel mielage and raise emissions
3) oil pressures can be changed, which can effect even the opening of the oil filter's bypass valve.
While there are 0w60 made (I think castrol R in Europe is one), they are designed for very special applications, and the cars themselves optimized for the recommendation.
Your Honda was spec'd for 10w30 for a reason. In synoil, you can use 5w30 or 0w30 as you choose to. In mineral oil, stick with 10w30 unless you live and drive in a very cold winter climate, where 5w30 may be needed.
So, use a 10w30 mineral above 0degF, or a 10w30 synoil for winter. In extreme cold, use a synoil.
If you race your car, or live in an area of extreme heat, a 5w40 synoil like "European Formula" Mobil1 might be a good choice.
What do i use? I plan to use either Amsoil 10w30 or the Series 2000 0w30 unless I see leaks. I also may use Red Line 10w30. I change once a year, which is only about 4000 miles for me.
I hope this helps.
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