Not going to matter 5W is 5W. It would not matter if iti was a 5W20 or a 5W50 they are going to behave like a 5W at test temp.'s! I run 0W40 and 5W40 dureing winter and summer and have no problems. FOr what it is worth I had Redline 5W40 in my engine one winter and it got down to something like -22°F or -25°F and the temp. when I got up to go to church was -18°F. My car turned over like it 70°F and fired right up. Their were only about 10 car's in the church parking lot that day. I would ignore any advice you get from someone saying that 5W40 is going to kill your engine but 5W20 is fine!
Best for winter: 5w20 or 5W40??
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Maybe easily pumpable (like 0W or 5W) does not mean that the oil will flow easily (which is more linked to viscosity). Therefore a 5W20 may have the same pumpability compared to a 5W40 but in addition the 5W20 may have a faster flow compared to that same 5W40 since the viscosity at any temperature is supposed to be lower. Therefore a 5W20 may be better for cold starts in winter (but it may be too thin at operating temps). Would this be a possible explanation to such remarks??
Yes, they will both test as a 5W at -35 degrees centigrade, but at temps of say, 0 to -10 degrees F, 5w-20 will be significantly thinner. Put the numbers into a viscosity calculator and see for yourself. Heck, many 10w-30s are thinner than 5w-40 at 0 degrees F.
I've often wondered something similar to what you are asking Kilou. Which would be better in NY winter (where 0*F is about the coldest temperature encountered) a 5w20 dino or a 5w30 PAO synthetic. The car is a Honda spec'd for 5w20 but I have both oils already in stock. Is the full PAO synthetic better used in the hot summer or cold winter? The car is my wifes and is used mostly for short trips.
I don't understand it either with respect to using a different oil in summer. However you can't take the two numbers independently. A 0w20 is much thinner (better) at low temperatures than a 0w40. See the graph below for more detail. You can't see the real cold temps but you can see where the viscosity is heading. A 0w40 is going no where near as low as a 0 or 5w20.
Hi,
this must have been posted 1000 times but there is simply too much threads on the topic of oil grades that as a "rookie" I'm a bit lost.
The general trend here seems to be that thinner oil is more recommended for cold weather and I can understand that. But I remember having read people writing that 5W40 would "kill" an engine quickly in extreme cold weather while 5W20 would be fine. Now my understanding of oil grade was that the first number is indicative of the pumpability of the oil when cold while the second number (after the W) is related to the oil viscosity at 100°C right? So independantly of the span between the two number (which should be as close as possible to restrict the amount of VI used....) I was thinking that the second number has no real influence for cold start in cold climates. Of course I understand that the thinner at 100°C, the thinner at -10°C (probably not so straightforward but as a rule of thumb it might be OK). The problem is that no matter what's the outside temperature, whether it is 35°C in summer or -25°C with freezing rain, my engine (coolant temp) works steadily around 87°C so I'd say the second number must be chosen accordingly to the working temperature of my engine and not with respect to the outside temp. On the other hand, for cold starts in winter, it is important to have a good pumpability hence a low first number (like 0W or 5W). Therefore I do not understand why people would recommend a 5W20 in winter and probably go for a 5W40 in summer because they need a thicker oil then.....because their engine works always at the same temp no? For winter I'd say a 0W or a 5W is better than a 10W or a 15W but why is the second number also important??
I know I'm wrong but tell me where
this must have been posted 1000 times but there is simply too much threads on the topic of oil grades that as a "rookie" I'm a bit lost.
The general trend here seems to be that thinner oil is more recommended for cold weather and I can understand that. But I remember having read people writing that 5W40 would "kill" an engine quickly in extreme cold weather while 5W20 would be fine. Now my understanding of oil grade was that the first number is indicative of the pumpability of the oil when cold while the second number (after the W) is related to the oil viscosity at 100°C right? So independantly of the span between the two number (which should be as close as possible to restrict the amount of VI used....) I was thinking that the second number has no real influence for cold start in cold climates. Of course I understand that the thinner at 100°C, the thinner at -10°C (probably not so straightforward but as a rule of thumb it might be OK). The problem is that no matter what's the outside temperature, whether it is 35°C in summer or -25°C with freezing rain, my engine (coolant temp) works steadily around 87°C so I'd say the second number must be chosen accordingly to the working temperature of my engine and not with respect to the outside temp. On the other hand, for cold starts in winter, it is important to have a good pumpability hence a low first number (like 0W or 5W). Therefore I do not understand why people would recommend a 5W20 in winter and probably go for a 5W40 in summer because they need a thicker oil then.....because their engine works always at the same temp no? For winter I'd say a 0W or a 5W is better than a 10W or a 15W but why is the second number also important??
I know I'm wrong but tell me where
I think you're mostly correct. In air cooled applications where the oil might not get as hot in the winter a thinner oil such as a 20wt might make more sense than a 40wt. Even cars without oil coolers might see a temperature difference from cold weather to hot weather so going from a 20wt to a 30wt or froma 30wt to a 40wt might make sense. I typically just follow what the manufactures recommend personally but it doesn't get super hot in the summer where I live most of the time.
Good point! 10W30 may be thinner than 5W40 at 0 degree F but although this is tested at -35°C the 5W remains more "pumpable" than a 10W at 0 degree F too, no? So at 0 degree F, what would be the benefit to have a thinner (W30) but less pumpable (10W) oil than a 5W40??? Also what happen to the oil when the engine reaches normal operating temperature??
My understanding is that if an engine calls for a XXW40 oil, you should stick to a XXW40 all year round since the operating temp of the engine won't change between summer and winter (liquid cooled engine). Then you can go down to a smaller first number (before the W) to have a better pumpability for winter and it's not bad to have a better pumpability in summer too. However going to a XXW30 in winter to have a thinner oil at startup would mean that your oil will be thinner at operating temp too....which is not so good if your engine calls for an SAE40 for example. So basically, aside of the problem of more VI being used in such oils which can be dealt by more frequent oil changes if really required, 0W40 or 5W40 are the best oils IMHO. The only reason I'd go for a lower weight like a 5W30 or 5W20 would be if my engine NEVER reach operating temp like in very short trips for example but that's really extreme.
I agree and you could only extrapolate the "curves" I gave only so far - possibly to the freezing range or a bit lower. At some point they will head north big time.
However, you may want to take a few points from your graph and plot them on a graph with a log Y scale. Currently the scale is linear, and viscosity vs temperature will plot as a curve even in the range I showed if you use a linear viscosity scale. The curve on the graph you posted will probably flatten out a lot when converted to a log scale.
[ August 21, 2006, 08:20 PM: Message edited by: Ron AKA ]
Liquid cooling still allows for variation of oil temp with ambient temp. Remember that oil is mostly cooled by air flowing next to the oil sump.
This is why oil recommendations used to be different for different ambient temps. Now we see only one grade recommended so the public would not be confused and more importantly, used the same grade as it was used for EPA fuel efficiency testing (in USA).
Back in the good old days, when I worked in New York, I ran a 351 cube-inch Ford Bronco with Castrol HD-30 monograde dino in the crankcase.
Even on days when we had to use shovels to dig our cars out of their tombs of snow & ice, that Ugly sucker fired right up!!!!!!
So, don't believe the marketing of Big oil that tells you you gotta have 0w-20 if you want to get somewhere in Winter!!!!!
Starting and engine health are not the same thing. I don't like to get stuck in winter, so I always put in the biggest battery that fits. Once started my Nissan 4x4 at -40 temperature without plugging it in. Three days later I was replacing the starter drive. Who knows what damage I did to the rest of the engine. Recall I was using a 10w40 conventional in those days.
You only have to try to pour a bottle of straight 30 in those kind of temperatures to understand what is happening inside the engine. Not good.
You only have to try to pour a bottle of straight 30 in those kind of temperatures to understand what is happening inside the engine. Not good.
Ron AKA posted a nice graph of oil viscosities for most temps, but one has to remember that viscosities can be highly non-linear at anything below -20°C as shown in this graph comparing a PAO with a VHVI Grp III, with and without PPDs.
One thing you need to consider is how often the car will be started with the oil at "test temperatures" vs. real world temperatures. Currently I've got Valvoline 5w-40 Premium Blue Extreme in my car, and Amsoil 10w-30/30 ACD in my wife's car. Even at 0 deg C, the 10w-30 is THINNER than the 5w-40.
Dave
Dave
Actually, not that extreme.
I have a 13 mile drive to work, which is not the shortest commute anyone has ever heard of.
Oil temps in a lot of cars don't make it up to true operating levels for half an hour. My drives are twenty minutes.
That means my 5W20 is likely at hot-temp SAE 40 viscosity by the time I make it to work...
Been there, done that, way before you showed up.
It's also the reason none of the numerous viscosity charts I've posted in the past go below -20°. And if your dealing with non-synthetics, there's the Gelation Index to consider.
This isn't real complicated....
A 5w-20 and 5w-40 may both have the same CCS viscosity @ -30C. However as soon as you start to heat them up, the 20wt is going to thin out much faster than the 40wt. Compare the relative viscosities @ the +40C temp posted on most spec sheets and you'll see what I mean. Basically at any temp > CCS temp the 40wt will be thicker, even at say -25C.
A 5w-50 will thin out even slower than the 5w-40, so it's an even worse choice for very cold temp use than 5w-20 or 5w-30.
TS
A 5w-20 and 5w-40 may both have the same CCS viscosity @ -30C. However as soon as you start to heat them up, the 20wt is going to thin out much faster than the 40wt. Compare the relative viscosities @ the +40C temp posted on most spec sheets and you'll see what I mean. Basically at any temp > CCS temp the 40wt will be thicker, even at say -25C.
A 5w-50 will thin out even slower than the 5w-40, so it's an even worse choice for very cold temp use than 5w-20 or 5w-30.
TS
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