# What Viscosity Do I Need?



## pipo (Oct 15, 1999)

Having seen a lot of questions on this forum about what viscosity oil to use for specific cars, whether old or new, it may be useful to read the following from bobistheoilguy:

"The best way to figure out what viscosity of oil you need is to drive the car in the conditions you will use. Then use the oil viscosity that gives you 10 PSI per 1,000 RPM under those circumstances. For some reason very few people are able to get this simple principal correct. I cannot explain further.

These same rules apply to engines of any age, loose or tight. Just because your engine is old does not mean it needs a thicker oil. It will need a thicker oil only if it is overly worn, whether new or old. Yet the same principals of 10 PSI per 1,000 RPM still apply. In all cases you need to try different grade oils and see what happens. Then choose the correct viscosity."

Pretty simple and straightforward, if you have an oil pressure gauge (which is not helpful, unfortunately, for a lot of us). 

He focuses a lot of attention on the fact that most engine wear occurs at start-up, when the oil is not up to operating temperature, and always too thick to lubricate properly. It's probably fair to summarize his advice by saying that the best oil viscosity for a particular application is the thinnest oil that will provide the required oil pressure at operating temperature, and that in most cases, going to a thinner oil than you may think you need will be the better choice. 

That's what he did with his Ferrari 575 Maranello, in which he uses 0W20. He said it had about 5,000 miles on the clock. He went on to say that there will be a day (estimate is 50,000 miles) when he will have to go to a 0W-30, and then in the future, a 0W-40, then a 0W-50, maybe.

Here are a few other points he makes about choosing the right oil:

"I truly believe that oil is much better being too thin than too thick. Over the years we have been going to thinner and thinner oils despite hotter engines with turbos and the like. The tendency is that people figure they need a 40 grade oils but then use a 50 instead. Better thinking is that if you think you need a 40, use a 30 grade oil instead. I firmly believe this based on all I know about oils."

"Older automotive owner manuals often recommended one oil for the summer and another for the winter. This is still necessary for air cooled engines but is no longer a consideration in pressurized water cooled engines. These engine blocks are kept at around 212°F all year round. The oil is around the same temperature as well. This allows for a single grade oil all year round. "

"People often say that their old 1980 car manual says to use a specific Brand-X motor oil. They keep trying to locate these older oils. First, just about any oil brand that meets the original specifications will do. Second, all oils are much, much better now.

"It is said that 90 percent of engine wear occurs at startup. If we are interested in engine longevity then we should concentrate our attention at reducing engine wear at startup."

"A main advantage that the synthetic has over the mineral based oil is the ability to lubricate at startup. Both types of oil have the same specifications at 104°F, 212°F and 302°F. It is the startup viscosity characteristics that separate these oils. Synthetic oils do not thicken as much on cooling. They have better fluidity as the temperature drops."


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## biggs88 (Mar 6, 2011)

pipo said:


> Having seen a lot of questions on this forum about what viscosity oil to use for specific cars, whether old or new, it may be useful to read the following from bobistheoilguy:
> 
> "The best way to figure out what viscosity of oil you need is to drive the car in the conditions you will use. Then use the oil viscosity that gives you 10 PSI per 1,000 RPM under those circumstances. For some reason very few people are able to get this simple principal correct. I cannot explain further.
> 
> ...


Use the oil that is spec'ed by the engine maker for your application.

Simple. To the point.


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## pipo (Oct 15, 1999)

biggs88 said:


> Use the oil that is spec'ed by the engine maker for your application.
> 
> Simple. To the point.


Well yes, but also no. The post was about viscosity, not whether or not to use manufacturer spec'd oil. 

Within the VW 502 approved oils, for example, there is a range of viscosities and formulations. And the point of the original post is to provide some background knowledge to better understand why a particular range of viscosities is chosen for a particular application.

If you're not interested, that's fine. The info is there for people who are.


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## uNclear (Aug 30, 2011)

pipo said:


> Well yes, but also no. The post was about viscosity, not whether or not to use manufacturer spec'd oil.
> 
> Within the VW 502 approved oils, for example, there is a range of viscosities and formulations. And the point of the original post is to provide some background knowledge to better understand why a particular range of viscosities is chosen for a particular application.
> 
> If you're not interested, that's fine. The info is there for people who are.


I get that some people are interested and do UOA and the like but I just see it as WAY over thinking what has already been proven! I think it's funny how religious some people are about it! Especially when those people don't even put that many miles on their cars or keep them that long! :screwy: :laugh:

For my application 0W40 covers it! :wave:


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## biggs88 (Mar 6, 2011)

pipo said:


> Well yes, but also no. The post was about viscosity, not whether or not to use manufacturer spec'd oil.
> 
> Within the VW 502 approved oils, for example, there is a range of viscosities and formulations. And the point of the original post is to provide some background knowledge to better understand why a particular range of viscosities is chosen for a particular application.
> 
> If you're not interested, that's fine. The info is there for people who are.


Yes. Useing the correct weight oil is important. 

Car makers set the viscosity range for their engine. Useing what they recommend would be wise on a stock or near stock engine.

Viscosity plays a role in engine wear, engine cooling, engine timing, VVT, oil PSI, ect. . . .


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## 90crvtec (Nov 17, 2010)

pipo, what you're reading is a post from AEHaas. He is quite the champion of using thin oils and also tends to back them up with UOAs. He's posted UOAs of several of his high end cars running very thin oils. 

If I recall, I think he has a UOA posted for his Lambo Murcielago with Fuchs Titan 0w20.

Anyways, AEHaas has some great arguments and I agree with him. There are a few things to consider based on his experiences and assumptions.

1) His ultra high performance cars have absolutely overkill oiling systems. In the case of his Ferrari and Lamborghini cars, they have a dedicated dry sump oil system that holds a massive amount of oil (anywhere from 8-12qts is not uncommon on those cars). A system like this is vastly different from a 4.5 qt wet sump oiling system in a Volkswagen and will yield consistent oil pressure, even with "thin" oil.

2) AEHaas correctly points out that oil pressure does not = flow. Most people don't get this. They want to see high oil pressure. If you have 0w20 @ 10PSI or 20w50 @ 30PSI, which will flow more? This theory is why most thin oils work so well in cars that specify a heavier oil, even though the thin oils might make less oil pressure, they flow more oil at that lower pressure, thus negating a lot of the value of oil pressure in the first place. Obviously, we still need SOME amount of oil pressure to move the lubricant around, but oil pressure and oil flow are not directly related when comparing two different viscosities of fluid.

3) The ultra high performance cars that AEHaas owns also have incredibly efficient oil cooling systems. AEHaas himself admits that his Ferrari does a very good job at keeping the oil cool. On a road car with a small sump and a high temperature thermostat, we have the reverse. Our cars are designed to run hotter and stay hotter, because that's when the engine is most fuel efficient and produces the lowest emissions. The problem here is that this also means that we will have a more narrow operating range for the oil in our engines, and I believe this is why auto manufacturers stubbornly stick with outdated oil specs, such as VW502.00. They want to have a thicker oil in there that will still be a thin 30 weight when the car is running 100mph in 95 degree weather with 3 people and luggage in the car. 

So while I agree completely with AEHaas' proposals and logic, it doesn't always apply verbatim to lesser engineered cars. The range of viscosities and formulations within VW502 is actually smaller than you might think. The common denominator here being that the most of the older German certifications will require 3.5HTHS to meet the cert. BMW LL-01 and VW 502.00 being two of them. 

This means that a 0w30 VW 502, a 5w30 VW 502, and a 0w40 VW 502 are all going to be very close in viscosity, close enough in fact that I don't think most engines would be able to tell the difference. If we look at the actual specifications of these oils, their viscosity @ 40C and their viscosity @ 100C, we see that they aren't really that different, even though one would think that a 0w30 and a 5w40 would be worlds apart. The common certifications keep them all in a pretty narrow window even though the labels would lead us to believe otherwise. 

Obviously, the 0w oils are going to perform better in the extreme cold but, they are still a good bit thicker than a 0w30 that does not have an HTHS of 3.5. Basically, the HTHS of 3.5 is the common denominator here that keeps this window of performance so small between all of the VW502 oils.

Looks like a lot of your quotes are from AEHaas' motor oil 101 article. Here's a link to the Ferrari Chat version for anyone else interested on reading the whole thing. I've been actively following BITOG since 2005 and AEHaas Motor Oil article was one of the first things that got me interested in motor oil: AEHaas Motor Oil 101


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## pipo (Oct 15, 1999)

uNclear said:


> I get that some people are interested and do UOA and the like but I just see it as WAY over thinking what has already been proven! I think it's funny how religious some people are about it! Especially when those people don't even put that many miles on their cars or keep them that long! :screwy: :laugh:
> 
> For my application 0W40 covers it! :wave:


I think you're right, uNclear, about everything you said. 

This is WAY overthinking, but that's part of the reason some of us are fanatics and ask stupid questions on enthusiast forums. And there's a big difference between overthinking and overdoing: I tend to be pretty conservative on the doing side of things, and have decided to stick with M1 0W-40 for the time being (easy choice), although I may top off with unapproved M1 0W-30 during the winter if I experience any consumption, to get the cold weather viscosity down a notch.

The other thing is, it feels good to baby our cars, and use products that we reasonably believe are best for the application. It may be overkill, but using a good oil may increase longevity, reduce service needs, improve mileage, improve power delivery, etc., and not all approved oils are created equal. That said, M1 0W-40 seems to be a great oil in many respects, especially considering that it is probably in the same league as or better than some of the premium oils but can be had for $6 and change per quart. 

Also, I am one of those guys who runs their cars way over 100,000. My X3 has about 140,000 on it and going strong, and I just got rid of an Audi that had more than 160,000. The Audi, for the most part, ran on NAPA brand 5W-30 full synthetic, and seemed to love it. That was before I got Religious! 

Sorry to all if I got a little defensive before...


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## pipo (Oct 15, 1999)

90crvtec said:


> pipo, what you're reading is a post from AEHaas. He is quite the champion of using thin oils and also tends to back them up with UOAs. He's posted UOAs of several of his high end cars running very thin oils.
> 
> If I recall, I think he has a UOA posted for his Lambo Murcielago with Fuchs Titan 0w20.
> 
> ...


Nice post; it's good to understand the perspective of a Ferrari/Lamborghini owner, with their superior lubrication and cooling systems. 

Another bit of religion I've learned is that the 40/100 degree C viscosities do not correlate well with operating temperature viscosity, which correlates much more closely with HTHS viscosity. So the HTHS Viscosity and the Viscosity Index are probably the most important available information in deciding how well an oil will maintain proper viscosity at widely varying oil temps. That's why M1 0W-40 is so attractive: 502 approved, and higher viscosity index than most if not all of the comparably priced oils, together with a more modern formulation than a lot of the other approved oils.

And your point about the viscosities of the approved oils not varying that much is even more true when looking at the HTHS viscosity. The differences between the oils seem to lie more in their ability to maintain viscosity and their formulations. 

Thanks for another informative post. :thumbup:


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## 90crvtec (Nov 17, 2010)

pipo said:


> Nice post; it's good to understand the perspective of a Ferrari/Lamborghini owner, with their superior lubrication and cooling systems.
> 
> Another bit of religion I've learned is that the 40/100 degree C viscosities do not correlate well with operating temperature viscosity, which correlates much more closely with HTHS viscosity. So the HTHS Viscosity and the Viscosity Index are probably the most important available information in deciding how well an oil will maintain proper viscosity at widely varying oil temps. That's why M1 0W-40 is so attractive: 502 approved, and higher viscosity index than most if not all of the comparably priced oils, together with a more modern formulation than a lot of the other approved oils.
> 
> ...


Thanks. :beer:

I assume you've also been using this link to calculate the viscosity of various oils at lower temperatures?
http://www.bobistheoilguy.com/viscosity-calculator/

The only thing that bothers me with calculations like that is that it depends on two viscosity numbers of relatively warm temperatures. For instance, viscosity @ 40C is still a long ways away from where the oil will be @ -8C. Where I live, it's not uncommon to have a solid month of temperatures -8C or even a little cooler.

We are kind of "guessing" how an oil will perform when we sample the 40C and 100C viscosities, and then try to correlate that to where we think the oil will end up at -8C. I don't quite trust those numbers. I really wish oil manufacturers would specify viscosity @ much lower temperatures, I think they would be quite revealing.


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## pipo (Oct 15, 1999)

90crvtec said:


> Thanks. :beer:
> 
> I assume you've also been using this link to calculate the viscosity of various oils at lower temperatures?
> http://www.bobistheoilguy.com/viscosity-calculator/
> ...


I actually used the Widman calculator at http://www.widman.biz/English/Calculators/Graph.html

One of the "oil professors" at BITOG said that the Widman calculator is useful down to about -10C. Between M1 0w-40 and GC, the M1 was significantly thinner at subfreezing temps than the GC, and eyeballing the viscosities and viscosity index of the other mass market 502 oils, it looked like M1 would easily beat them in this category as well.

It would be really useful if the manufacturers gave us cold climate folks viscosity measurements at say 0C (32F), -10C (14F) and -20C (-4F). In the meantime, we live with the 40C and 100C figures and the viscosity index. By the way, the viscosity index is calculated from the 40/100 viscosities. The closer they are to each other, the higher the VI, and the higher the better. I think I got that right! :snowcool:


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## gmikel (Nov 10, 2010)

*it takes hp to pump oil*

the thicker the more hp it rquires, in addition to all the above. and yes it is made way to complicated on this forum. use a quality oil of the spec recommended by the manufacturer, change it regularely and all will be fine. with the oil changes read the disclaimer that go with the rcommnded intervals. most of us will fall into a catagory requiing somewhat more frequent oil changes.


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## Super Hans (May 27, 2011)

I like to shoot for 5000cP as the floor for cold starting. 10,000cP being the absolute acceptable limit....imo.

The "speced" 5w-40 really doesn't cut it in cold, does it?









Shot at 2011-08-26

That's why 0w- oils were invented. 

I dunno if people realize how thin of a 40 weight M1 0w-40 is. Let's just say it shears into a 30 weight after 500 miles....thinner than GC, which does not shear.

Mobil 1 SyperSyn fairs poorly in general when exposed to fuel dilution, another Mobil 1 trademark, along with high iron wear. If more people here were pulling UOAs, you'd know that.


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## gmikel (Nov 10, 2010)

*way to complicated*



Super Hans said:


> I like to shoot for 5000cP as the floor for cold starting. 10,000cP being the absolute acceptable limit....imo.
> 
> The "speced" 5w-40 really doesn't cut it in cold, does it?
> 
> ...


as has been said, it's been made way to complicated


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## gmikel (Nov 10, 2010)

*sorry soup*



Super Hans said:


> I like to shoot for 5000cP as the floor for cold starting. 10,000cP being the absolute acceptable limit....imo.
> 
> The "speced" 5w-40 really doesn't cut it in cold, does it?
> 
> ...


the chart shows 5w-40 mobil 1 not 0w-40, another missed boat.


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## uNclear (Aug 30, 2011)

But it is very pretty and well layed out...........it just isn't of any use.


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## pipo (Oct 15, 1999)

gmikel said:


> the chart shows 5w-40 mobil 1 not 0w-40, another missed boat.


You're right, gmikel, and of course the M1 0W-40 has much lower cold temp viscosity than the M1 5W-40. And while the cold temp viscosity of M1 0W-40 and Edge 5W-30 are very close down to freezing, but M1 does better starting at about 14F (-10C). 

The M1 0W-40 would have been the winner if it had been shown on the chart.

The other thing is - and here I am just repeating what someone said - that these charts are really only valid down to about -10C, and even at that temp the accuracy may be suspect. So the 5000 cP floor may be a nice goal, but we can't really determine whether an oil meets it at -30C based on these charts. Someone would actually have to take the measurements.


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## Super Hans (May 27, 2011)




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## uNclear (Aug 30, 2011)

Why do you keep posting useless charts and graphs!? :facepalm:

Are you selling something?
Are you proving something?

All your other posts that don't have graphs and charts just say how great "highmiles" is?

You need a new hobby! :screwy:


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## gmikel (Nov 10, 2010)

:thumbup:


uNclear said:


> Why do you keep posting useless charts and graphs!? :facepalm:
> 
> Are you selling something?
> Are you proving something?
> ...


:thumbup::thumbup::thumbup::thumbup::thumbup::thumbup::thumbup:


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## Super Hans (May 27, 2011)

It must be frustrating to try and learn from a technical forum, when you obviously have no technical background and simply do not understand the charts. 

Obviously a product of the public school and state university system, I bet you could name the top 5 teams in every sports division. :thumbdown:


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## Super Hans (May 27, 2011)

lol.










Shot at 2011-07-16


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## gmikel (Nov 10, 2010)

*soup*



Super Hans said:


> It must be frustrating to try and learn from a technical forum, when you obviously have no technical background and simply do not understand the charts.
> 
> Obviously a product of the public school and state university system, I bet you could name the top 5 teams in every sports division. :thumbdown:


you've been banded under multiple user names both here and on bigtog. you can post fancy charts and graphs but you haven't the sense of a goose, sorry.


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## uNclear (Aug 30, 2011)

gmikel said:


> you've been banded under multiple user names both here and on bigtog. you can post fancy charts and graphs but you haven't the sense of a goose, sorry.


And Super Douche, you are a condescending prick! Just because you can post some crap chart doesn't mean you know sh!t........did you make the chart?.......did you do the research behind the chart?..........it's nice to dream that you are smarter than everyone else but it doesn't make it so. 

I don't watch NBA, MLB, NFL or NASCAR but to think you are so much better than the people that do shows your insecurities and lack of intelligence! 


Seem funny to make fun of your public school system, I wasn't educated in the US! I was brought here because of people like you! 

:wave:


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## 90crvtec (Nov 17, 2010)

C'mon guys, it's just oil. Everybody have a beer and chill out. :beer:


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## pipo (Oct 15, 1999)

*I Second that Emotion...*



90crvtec said:


> C'mon guys, it's just oil. Everybody have a beer and chill out. :beer:


Why don't we try to take the best of what each of us has to offer and try to ignore the rest? We'll get along better and learn more in the process.

Healthy disagreement develops knowledge and is sometimes entertaining. Name calling and insults are probably not helpful.

Just take a deep breath and repeat 10 times: oil is good, oil is good, oil is good...


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## Super Hans (May 27, 2011)

Yeah, you definitely want to jump in with both feet on a technical forum, when you have no technical skills. 

What was your special skill again?



Quit breaking the pills in half.


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## jellowsubmarine (Aug 24, 2011)

pipo said:


> Why don't we try to take the best of what each of us has to offer and try to ignore the rest? We'll get along better and learn more in the process.
> 
> Healthy disagreement develops knowledge and is sometimes entertaining. Name calling and insults are probably not helpful.
> 
> Just take a deep breath and repeat 10 times: oil is good, oil is good, oil is good...


:thumbup:
This is a forum, I'm sure many have listened and learned. I for one appreciate the sharing and found this great info. I certainly have alot to learn, listening and sorting out the details for oneself doesn't make you inferior.

keep up the good tech info. pipo


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## pipo (Oct 15, 1999)

jellowsubmarine said:


> :thumbup:
> This is a forum, I'm sure many have listened and learned. I for one appreciate the sharing and found this great info. I certainly have alot to learn, listening and sorting out the details for oneself doesn't make you inferior.
> 
> keep up the good tech info. pipo


Thanks, jellowsubmarine. One big happy family!


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