# Difference between 0W-40 and 5W-40?



## Nadhir (Jan 22, 2015)

I just got a 2006 VW Passat 3.6L 4motion and have been looking up what oil I need for it. 

I read 5W-40 and 0W-40 were the best oil types - brands aside - but don't really know the difference between the two. All I really know is that one is thicker than the other (not sure which one) and I'm not sure what difference it may cause, if any at all. 

Car has over 100 miles, if that means anything with the oil type.


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## crrdslcvr6 (May 3, 2006)

Nadhir said:


> I just got a 2006 VW Passat 3.6L 4motion and have been looking up what oil I need for it.
> 
> I read 5W-40 and 0W-40 were the best oil types - brands aside - but don't really know the difference between the two. All I really know is that one is thicker than the other (not sure which one) and I'm not sure what difference it may cause, if any at all.
> 
> Car has over 100 miles, if that means anything with the oil type.


0w40 will have better flow characterizes in cold and usually sheer a bit in the heat down to a 30 weight oil. 5w40 will be a thicker oil that will maintain viscosity in the heat better. Good oil can be had in both categories, take your pick.


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## Nadhir (Jan 22, 2015)

crrdslcvr6 said:


> 0w40 will have better flow characterizes in cold and usually sheer a bit in the heat down to a 30 weight oil. 5w40 will be a thicker oil that will maintain viscosity in the heat better. Good oil can be had in both categories, take your pick.


So should I use the 0W-40 in the winter time and the 5W-40 in the summer or does it not matter all that much?


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## crrdslcvr6 (May 3, 2006)

Nadhir said:


> So should I use the 0W-40 in the winter time and the 5W-40 in the summer or does it not matter all that much?


You can but either oil will work. If your winters are brutally cold I would use 0w-40 year round. If your engine runs a bit warm use 5W-40.
I run 5W-40 in my vr6 corrado and 0W-40 in my 330ci year round. Both cars have over 115K miles and both run great.


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## racerpoet (Apr 20, 2013)

Per VWoA:



> SAE 5W-40 or SAE 5W-30. Synthetic based oils. Engine oil must conform to the exact specification in VW publication VW 502 00. See TSB No. 17 09-07 (2012855).
> 
> Use only a high-quality engine oil that expressly complies with the Volkswagen oil quality standard specified for your vehicle's engine. Using any other oil can cause serious engine damage that will not be covered by any Volkswagen Limited Warrantly. DO NOT mix any lubricants or other additives into the engine oil. Doing so can cause engine damage. Damage caused by these kinds of additives are not covered by any Volkswagen Limited Warranty. Overfilling engine oil can cause misfire DTC's to be stored in the Engine Control Module (ECM) -J220-. To prevent overfilling, add approx. 0.5 less than capacity, start engine and let it run until engine operating temperature is approx. 140Deg. F (60Deg. C), turn OFF ignition, wait approx. 3 min., check dipstick, then fill to MAX. TURBO ENGINES ONLY: After changing oil and filter, start and run engine at idle until oil pressure light goes out. DO NOT rev engine, as this could cause damage/failure of the turbocharger. Quantities are approximate.


You can use whatever oil you want, it's your car. It is recommended that you use a synthetic oil meeting the Volkswagen 502 00 oil specification.


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## goldblumjeff01 (2 mo ago)

crrdslcvr6 said:


> You can but either oil will work. If your winters are brutally cold I would use 0w-40 year round. If your engine runs a bit warm use 5W-40. I run 5W-40 in my vr6 corrado and 0W-40 in my 330ci year round. Both cars have over 115K miles and both run great.


 If your engine is running a bit warm a thicker oil will make it run hotter. Cuz friction.


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## Butcher (Jan 31, 2001)

WHAT? 

That is not right.


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## goldblumjeff01 (2 mo ago)

Butcher said:


> WHAT?
> 
> That is not right.


It absolutely is. Common sense. It's called fluid friction or viscous drag. A thicker fluid takes more energy to move around, fluid friction increases with viscosity. That's how these thin 0w20 and 0w16 oils improve fuel economy, and why we use water as coolant instead of syrup. There's even a formula. Fluid Friction=-nA(dv/dy) where n=viscosity.
Amsoil explains


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## Butcher (Jan 31, 2001)

It is not.

When the engine is at full operating temperature, they are both at the 40 rating. Since that is the case, there is no loss. I bet the light bulb just turned on 💡

I bet you could not measure the cold running efficiency losses, since we are only talking about 0 vs 5. As a professional mechanic for over 40 years [38 just on German cars], I have never ever had a customer complaint that the engine is running too hot during a cold start. 

With the thousands of cars that I have dealt with or know about, changing the oil with a thinner oil has never fixed an engine running too hot. Matter of fact, it has never fixed anything except for the shop making more money. So, your thought is not just wrong, it's misleadingly wrong. People read these posts and when people like you post this stuff, others get misled.

For 20 years, I used to fix Mercedes that could not be fixed. I took all the information that I read/heard and took it with a grain off salt. Most of the information I heard is poor at best. The stuff I read from the Mercedes Benz documents were much more accurate, but they still had problems. 

I suggest that you question everything you read and try to make sense of it. 

But heck, if you want to think you are right, great. The rest of the world deals with reality.


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## goldblumjeff01 (2 mo ago)

Butcher said:


> When the engine is at full operating temperature, they are both at the 40 rating. Since that is the case, there is no loss. I bet the light bulb just turned on 💡


That's a significant misunderstanding of how cold weather ratings are actually achieved and their effect on high temperature performance. There is a difference, although pretty tiny between a 0w40 and a 5w40, at all operating temperatures. It will vary considerably between brands depending on base stock and VI modifiers, but typically a 0w40 will shear down to a thinner oil at operating temps than a 5w will due the inclusion of a higher percentage of VI modifiers. Between 0w and 5w it's pretty moot, that would depend more on the brand and the formulation they used, it would be more consistent if you compared 10w40 or 15w40 with a 0w40. A 0w40 is more likely to shear and perform like a 0w30 after a few weeks because it requires a higher percentage of, less shear resistant than the base stock, VI modifiers to achieve that 0w rating. A 10w40 can start with a thicker base oil and doesn't need to add as many modifiers producing a more sheer stable oil and can remain more viscous overtime, keeping the properties of a 40 weight oil over time and not shearing down to a 30.

It's not so simple as "they're all the same at 100C because they're all 40s. Think about it- if all 40 weight oils, from 0w40 to 25w40, all performed the same at operating temperatures as each other, then why would there even be 5w40 oil? Why wouldn't every manufacture just recommend 0w40 and cover the widest range?



Butcher said:


> I bet you could not measure the cold running efficiency losses, since we are only talking about 0 vs 5.


We absolutely can measure them, and we do. But like you imply and I said above, the differences between a 0w and a 5w are so small it would be better to measure the differences between individual brands even year by year than to assign a rating across the board.



Butcher said:


> With the thousands of cars that I have dealt with or know about, changing the oil with a thinner oil has never fixed an engine running too hot.


No it definitely won't. If your engine is running hot the viscosity or the oil isn't the reason and making it thinner definitely isn't going to help. Making it thicker isn't going to help either. That's not addressing the cause. But this is irrelevant, I'm talking about fluid physics you're taking about how to fix a coolant leak.


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## Butcher (Jan 31, 2001)

If I recall, the topic is 'What is the difference between 0W40 and 5W40'. We should probably keep on track. 

You piped in saying *IF* your car was running slightly warm, the thicker oil may be the cause. I stated you are wrong and shared my 40 years of real world experience proving that. Of course, that is my opinion and I could be just lying. I'm not but if you think I am, I'm ok with that. 

I think it would be best to keep on track instead of broadening the road to some things I may agree with.

Yes, you can measure the differences in weight of the oil. That is a no brainer. That is why they are rated differently. I said I highly doubt if you could prove the differences in any test. I was implying real world tests. Just like running an engine on a dyno, some days are better than others. There are too many variables that could cause the differences. Remember, the subject is 0W40 and 5W40. Not any of the weights you are bringing to the table.

Why do manufacturers have their recommendations? From my understanding, when they design a product, they use certain oils and ask the oil manufacturers what they recommend. Sometimes the goal is maximum efficiency, others it make be maximum power, others may be long term durability/use, emissions, does the engine have catalysts, diesel/gas, etc. Let's accept the fact that neither of us know. Asking a question that you do not have the answer is just like me answering that question. We have our beliefs, but lets face it, we are both wrong. Unless you are designing engines for a manufacturer, I don't and I do not think you do either.

Who's talking about coolant leaks? I missed that. I suggest we stay on topic. Makes a discussion flow easier [yeah, pun intended].

One thing I find fascinating. What is with it about Americans and engine oil weights? As a professional tech that owns a shop, the most important thing for me is getting the right spec oil. Working with Mercedes, engines with issues had the oil sent out for testing. We knew right away if the right oil was put in and there were some angry clients when we told them the oil used was not up to spec. 

The second most important thing for me is the brand. I am willing to spend more of my clients money for a name brand oil. People really defend their brand and say all others are junk. I guess it's like kids, not many parents think their kid is bad, even though we all know they are. If you like Mobil 1 great. If you like Amsoil, wonderful. I would not put Amsoil in any of my clients cars. #1, my supplier does not stock it and #2, it's all just hype. Is it bad? No, I do not believe that at all. In a nut shell, I do not believe any oil will go much past 10k and one year of service. I have no proof of this and I know I am wrong. I've never seen any engine fail when the oil services are done properly [time and proper oils/filter]. 99.9% of my clients are not going to keep their engine past 200k. There is no reason to put in 'better' stuff if there is no benefit to my clients. Who cares if the oil lasts 20k? I'm swapping it out at 10k. Who cares if the oil lasts 5 years? I'm swapping it out in a year. Who cares if an oil filter captures every micron so it lasts 1,000,000 miles? The engine is going to be made into HF tools in 200k. Of course, if we are talking about ships, where they build the ship around the engine, that is different, but we are staying on track.

The last thing that is most important is the oil filter. OEM is the only way to go. Again, working with Mercedes, oil filters were also tested and if they were not up to specs, there was a really good chance that it would be denied any warranty coverage. 

I am 100% confident that what the factories recommend is done with testing. Testing that you/I do not have the privilege of knowing or being a participant in.

The only reason to look at oil weight is where you live. Rumor has it, Santa Claus uses a good 0W40 and Satin uses 10W60. My source of this information is from Big Foot and we all know he lies a lot. 

In the end, I believe you are wrong, in the real word scenario, when you say the the engine may run warmer if you use a 5W40 oil vs 0W40. I believe as long as I use oil that passes VW spec [or whatever manufacturer I am servicing], use a OEM oil filter, and use the right weight for my area, I am good to go.


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## Boner Champ (May 9, 2013)

Some 5w-40 can be quite thick in cold.









The 0w-30 here is German Syntec, and trust me it's the same visc curve as 0w-40.
As you see, 5w-40 is 3-4x thicker in cold than jug 5w-30

As far as 0w-40, there's no downside, but do you actually need the improved cold performance? it's a combo of climate and engine. Where a basic N/A engine can crank and start with a cold visc of 10,000cSt (1000x the visc at operating temp!) turbo engines need good cold flow to lube well as it warms up, so 0w-40 or even 5w-30 is the ticket in cold. 5000cSt is a more reasonable cold visc for turbos. The danger is when you start to boost while the oil is still cold, which can be several miles for sake of discussion.

Another thing 0w-40 offers is better specs than 5w-40 in many cases. Euro 5w-30 VW 504 oil is actually the top performance spec, MB 229.5 beats out the lame VW 502 specs, which are often 5w-40, but product lines are changing with more 5w-40 MB 229.5 available. 






Relative Performance Comparison Tool for Passenger Car Specifications - Engine Oil Additives - The Lubrizol Corporation







online.lubrizol.com













One exception to the added cost of VW 504 family of MidSAPS oils is Pennzoil Euro L 5w-30. It's MB 229.51 and BMW LL04, but skips the added cost of a VW 504 approval. It's an amazing oil for $24 a jug, way better than Euro brands of VW 502 oils, lol.



Robot or human?



If you really want a 0w-40, Castrol Edge with titanium additive pack is a legit Euro made oil at WalMart with MB 229.5.

Liqui Moly is not appealing to me at all, I'd rather use a HD 5w-40 like Rotella at half the price, but whatever.


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## Boner Champ (May 9, 2013)

Mechanics are the worse source for lube info. If you have a tribology question, ask a real tribologist.


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## Butcher (Jan 31, 2001)

I agree 100% but on the other side of the coin, tribologist are a terrible source for repair information, ask a real mechanic.


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