I'd have figured that since things would have contracted so much at low temperatures that they'd use an oil with a higher viscosity at low temperatures, not lower.. Yes I understand moving parts at a high viscosity in frigid temperatures would be a major problem but what about the wear and tear of using a lower viscosity?
here is the better question, why would you use the higher viscosity oil (the W part) when you can use the lower one? I mean if they're the same viscosity when they're warmed up, and they generally choose the oil with a lower cold viscosity for cold climates, what would be the need for a higher cold viscosity then? I'd have figured that since things would have contracted so much at low temperatures that they'd use an oil with a higher viscosity at low temperatures, not lower.. Yes I understand moving parts at a high viscosity in frigid temperatures would be a major problem but what about the wear and tear of using a lower viscosity?
If it's all relative, then how would one find an oil consistency so that it's the same consistency when it's hot and cold? If using an arbitrary scale, where 10 is the consistency when hot, for a 5w-30 oil, what would the consistency be when @ 50F? If that 5w-30 is a 20 when @50F and a 10w-30 is a 30 when @ 50F, what is preventing the use of 0w-30 in place of the 5w-30 then? I mean after all it's not like the 0w-30 when @50F is going to be thinner than needed when it's hot, right? So really, from the sound of it, you can always use the lowest "W" viscosity since it will never be less than the viscosity when it's warm..1) All oil, even multi-grade oil, is thickest when cold and thinnest when hot. The weight range (e.g. 5w30) is not a description of absolute viscosity, but rather of viscosity characteristics. It means that, when the oil is cold, it behaves substantially similarly to a straight 5 weight oil and when the oil is hot it behaves substantially similarly to a straight 30 weight oil. This means that, even though it thickens when cold, it doesn't thicken as much as straight 30 weight would and that, even though it thins when warm, it doesn't thin as much as straight 5 weight would. Even when using 5w30 oil, it is thicker (more viscous) when cold than it is when hot.
2) The reason that lower weights of oil are preferred in very cold environments is because the higher an oil's viscosity, the more it resists the oil pump's efforts to build pressure. The thicker the oil, the longer it takes for the finer parts of the engine, such as the valvetrain, to be brought up to operating oil pressure. Lower weight oils allow the engine to "pump up" to operating oil pressure faster. This effect is especially pronounced in very cold climates. The oil's natural tendency to thicken when cold is more than sufficient to account for the increase in tolerances due to cold parts contracting even when using oils with very low cold weights.
ZV
If it's all relative, then how would one find an oil consistency so that it's the same consistency when it's hot and cold? If using an arbitrary scale, where 10 is the consistency when hot, for a 5w-30 oil, what would the consistency be when @ 50F? If that 5w-30 is a 20 when @50F and a 10w-30 is a 30 when @ 50F, what is preventing the use of 0w-30 in place of the 5w-30 then? I mean after all it's not like the 0w-30 when @50F is going to be thinner than needed when it's hot, right? So really, from the sound of it, you can always use the lowest "W" viscosity since it will never be less than the viscosity when it's warm..
If it's all relative, then how would one find an oil consistency so that it's the same consistency when it's hot and cold? If using an arbitrary scale, where 10 is the consistency when hot, for a 5w-30 oil, what would the consistency be when @ 50F? If that 5w-30 is a 20 when @50F and a 10w-30 is a 30 when @ 50F, what is preventing the use of 0w-30 in place of the 5w-30 then? I mean after all it's not like the 0w-30 when @50F is going to be thinner than needed when it's hot, right? So really, from the sound of it, you can always use the lowest "W" viscosity since it will never be less than the viscosity when it's warm..
So is the use of synthetic 0W-30 going to be better overall in terms of lubrication and efficiency as the use of 5w-30 dino oil? It sounds like to me you are saying that a straight 30 oil is going to last much longer than a 5 or 10w-30 oil would.. How much worse is a 0w-30 going to be in comparison to a 5w-30? Also is the increase in viscosity modifiers when going from 5w-30 to 0W-30 going to be higher than 5w-20 to 0w-20?3) Reasons for not using, say, a 0w30 instead of a 5w30 is that the greater the range between the winter weight (the "5w") and the standard weight (the "30"), the more viscosity modifiers that must be added to the oil. More viscosity modifiers means less base oil stock and consequently means less ability to lubricate as well as less ability to absorb contaminants safely without becoming acidic.
ZV
I didn't suggest using a heavier weight oil...:hmm:For someone that's so focused on fuel efficiency I'm surprised you're not proposing the thinnest oil possible. Oil functioning at the correct viscosity will have less parasitic drag on the engine while still providing good lubrication. Suggesting that they use a thicker oil than necessary would lower fuel efficiency.
For someone that's so focused on fuel efficiency I'm surprised you're not proposing the thinnest oil possible. Oil functioning at the correct viscosity will have less parasitic drag on the engine while still providing good lubrication. Suggesting that they use a thicker oil than necessary would lower fuel efficiency.
I didn't suggest using a heavier weight oil...:hmm:
1) All oil, even multi-grade oil, is thickest when cold and thinnest when hot. The weight range (e.g. 5w30) is not a description of absolute viscosity, but rather of viscosity characteristics. It means that, when the oil is cold, it behaves substantially similarly to a straight 5 weight oil and when the oil is hot it behaves substantially similarly to a straight 30 weight oil. This means that, even though it thickens when cold, it doesn't thicken as much as straight 30 weight would and that, even though it thins when warm, it doesn't thin as much as straight 5 weight would. Even when using 5w30 oil, it is thicker (more viscous) when cold than it is when hot.
2) The reason that lower weights of oil are preferred in very cold environments is because the higher an oil's viscosity, the more it resists the oil pump's efforts to build pressure. The thicker the oil, the longer it takes for the finer parts of the engine, such as the valvetrain, to be brought up to operating oil pressure. Lower weight oils allow the engine to "pump up" to operating oil pressure faster. This effect is especially pronounced in very cold climates. The oil's natural tendency to thicken when cold is more than sufficient to account for the increase in tolerances due to cold parts contracting even when using oils with very low cold weights.
ZV
Car manufacturers are doing precisely this. Most cars these days use 0 or 5W-XX to get better mpgeeez.
They did the same thing for the 3.9L V8 in the 1st generation Lincoln LSes.Ford issued a TSB recommending a switch from 5W-30 to 5W-20 on many engines going way back. The 3.8L V6 in my 1995 Taurus was included, for example.
I wonder if Honda has done the same with their 90s civics.. The reason why I ask is because despite the Honda D engine being in the '88-'05 civics, it's only the '01+ civics that mention 5W-20 while the previous civics mention 5w-30..They have gone to lower W numbers, actually. -20 instead of -30, to get the better economy. The first number probably doesn't affect FE much, if at all once the engine is warm.
Ford issued a TSB recommending a switch from 5W-30 to 5W-20 on many engines going way back. The 3.8L V6 in my 1995 Taurus was included, for example.
You didn't, but typically you're going nuts about every possible drop of gas you could save to the point where you want to start removing your power steering. For something that actually is a reasonable thing to think about when you're maintaining your car I'm surprised you didn't even mention fuel efficiency when picking oil.Posted by fleabag
I didn't suggest using a heavier weight oil...
I wonder if Honda has done the same with their 90s civics.. The reason why I ask is because despite the Honda D engine being in the '88-'05 civics, it's only the '01+ civics that mention 5W-20 while the previous civics mention 5w-30..