VW Oil Conversation - why 40 weight?

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Why do you suppose VW persists with the 40 weight oil specification (VW 502 00), when many competitors have been specifying 20 weight oils for many years with good engine longevity? Do passenger cars like the Passat and Jetta really need thick oil? For one thing, SAE 40 exacts a fuel efficiency penalty compared to SAE 20. VW must have spent a fortune redesigning their new gen-3 1.8T engine for improved efficiency (their stated goal), yet they seemingly shoot themselves in the foot by going with 40 weight. One would think the new engine would have been redesigned from the outset to work with 20 weight or at most 30 weight oil? My guess is that VW engines run hot (which is why they often come with oil coolers). So maybe 40 weight in a hot engine has the same viscosity as a cooler running Honda Civic engine with 20 weight oil? Just speculation, though. Or does VW assume we drive wide open on the Autobahn every day? Any thoughts on this?
 
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I have wondered this as well. I'm assuming it is because of the long change intervals. (10k mi./1yr.) I see no reason why you couldn't use a quality synthetic or blend for a 5-7500mi OC. The 2.5L in line 5 cyclinder engine is easy on the oil. Not Direct Injected nor Turbo-charged w/5.8Qt sump. I've used GC 0w-30 and the engine runs superbly w/this oil but I want to compare it w/Pennzoil Euro Ultra 5w-40. We'll see how it likes the Ultra...
 
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Bearing clearances and the need to make sure that the engine doesn't blow up if someone drives it no the autobahn at the speed limiter for extended period of time where the oil temperatures could get too high for lesser grades.
 
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Originally Posted By: SandCastle
Why do you suppose VW persists with the 40 weight oil specification (VW 502 00), when many competitors have been specifying 20 weight oils for many years with good engine longevity? Do passenger cars like the Passat and Jetta really need thick oil? For one thing, SAE 40 exacts a fuel efficiency penalty compared to SAE 20. VW must have spent a fortune redesigning their new gen-3 1.8T engine for improved efficiency (their stated goal), yet they seemingly shoot themselves in the foot by going with 40 weight. One would think the new engine would have been redesigned from the outset to work with 20 weight or at most 30 weight oil? My guess is that VW engines run hot (which is why they often come with oil coolers). So maybe 40 weight in a hot engine has the same viscosity as a cooler running Honda Civic engine with 20 weight oil? Just speculation, though. Or does VW assume we drive wide open on the Autobahn every day? Any thoughts on this?
First, engine is made for European use. When they design engine they are not thinking about us here first, then Germans. So yes, average German drives on Autobahn every day to get to work. That does not mean it drives every day 250km/h, but having a lot of experience in Germany, and other European countries, driving dynamic is much different. Second, it is philosophy in building engines.
 
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Originally Posted By: SandCastle
Why do you suppose VW persists with the 40 weight oil specification (VW 502 00),
First of all, VW does not persist with 40 grade oil. The spec calls for HT/HS viscosity of at least 3.5 cP, and as such, 30 grade oils can meet this requirement as well, and there are some VW 502.00 30 grade oils out there.
Quote:
For one thing, SAE 40 exacts a fuel efficiency penalty compared to SAE 20.
How much of a penalty is it really? As for the reasons why, I believe it mainly had to do with long drain intervals. If your 3.5+ cP HT/HS oil happens to thin out over the course of a long OCI due to shearing and fuel dilution, it'll still be viscous enough to provide adequate protection. The same may not be true if you start out with an oil that only has 2.6 cP HT/HS. However, I am now seeing some cars calling for 20 grade oils and recommending long drain intervals, too, so maybe they're not worried about a 20 grade thinning out even more.
 
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QP is right. They specify use of minimum 3.5 mPa.s HT-HS oils, not 40 grade. All Euro engines are higher stressed compared to most Asian or American engines. They usually have higher output per litre, bearing pressures and flat tappets. ACEA A3/B4 and C3 accommodate those needs.
 
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I've never read this before, but the idea came to me from my own experience... It's more common for Europeans to drive a manual shift transmisson than it is in the US. In stop-and-go traffic my Passat has no problem idling in gear when moving slow unless going uphill. This is when oil pressure is at it's lowest, and the thicker oil provides more protection for the bearings in this case.
 
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Let's not forget also that in Europeland these engines will commonly use 504 oils with a 5W-30 viscosity, up to 30,000 km OCI.
 
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Originally Posted By: weasley
Let's not forget also that in Europeland these engines will commonly use 504 oils with a 5W-30 viscosity, up to 30,000 km OCI.
30,000km is in ideal conditions. Also, 504. oils are very heavy, meaning they are close to 5W40.
 
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My point is that various contributors have declared that because of bearings and autobahns and 10k mile OCIs and manual gearboxes that the oil has to be 5W-40. The reality is that in the places where these factors are true (or worse), the commonly-used oil is 5W-30 (and, in fact, could even be a 0W-30). The VW 504 00 spec does not specify a 'heavy' 30, it requires only that the KV100 matches that of a SAE 30 grade (plus, of course, it has to be able to get through the numerous engine tests).
 
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Originally Posted By: weasley
The VW 504 00 spec does not specify a 'heavy' 30,
VW 504.00 specifies that HT/HS viscosity has to be at least 3.5 cP. In practical terms, it means the oil has to be a heavy 30 grade.
 
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Originally Posted By: weasley
My point is that various contributors have declared that because of bearings and autobahns and 10k mile OCIs and manual gearboxes that the oil has to be 5W-40. The reality is that in the places where these factors are true (or worse), the commonly-used oil is 5W-30 (and, in fact, could even be a 0W-30). The VW 504 00 spec does not specify a 'heavy' 30, it requires only that the KV100 matches that of a SAE 30 grade (plus, of course, it has to be able to get through the numerous engine tests).
VW 504.00 is "heavy" 5W30 oil since it requires HTHS of minimum 3.5cp, like Quattro already mentioned. Also, all 5W30 VW 504.00 oils are between 11.5 cst (very rear) and closer to 12 (often) and even 12.21 (M1 ESP 5W30). M1 ESP 5W30 is on the verge of being 5W40 (12.5cst). To illustrate how heavy is M1 ESP 5W30 take into consideration that Motul X-Clean 5W40 has HTHS of 3.64cp, while M1 ESP 5W30 has 3.58cp.
 
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A friend of mine owns a 2 year old turbo diesel VW Sharan and his local VW dealer is using 5W-30 oil with ACEA C3 specification. This is the oil they use in his car: http://www.autoteile-meile.ch/%C3%96le/Castrol/EDGE-Professional-Longlife-3-5W-30/p-OIL-239 As you can see, this is 5W-30 and not 5W-40. Perhaps this is caused by the fact the diesel engines run cooler and our motorways are limited to 120 km/h unlike German Autobahn.
 
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Current engine technology with variable flow oilpumps don't need only low viscosity for FE benefits. Friction modifiers and detergent systems can give similar. The need for VWs to use 3.5cp hths oils is a global requirement. The engines are designed for this viscosity. DPF regen with post combustion dpf strategies and bio diesel can result in fuel dilution thinning out the oil. The old PD engines need the correct oil otherwise the cams wear out. The right oil is both >3.5cp and the right chemistry add pack.
 
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Originally Posted By: volodymyr
A friend of mine owns a 2 year old turbo diesel VW Sharan and his local VW dealer is using 5W-30 oil with ACEA C3 specification. This is the oil they use in his car: http://www.autoteile-meile.ch/%C3%96le/Castrol/EDGE-Professional-Longlife-3-5W-30/p-OIL-239 As you can see, this is 5W-30 and not 5W-40. Perhaps this is caused by the fact the diesel engines run cooler and our motorways are limited to 120 km/h unlike German Autobahn.
That oil is appropriate for that car no matter where you drive it. The most important thing there is HTHS, and that 5W30 has HTHS of min 3.5.
 
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I'm guessing it's cheaper to make a 5w-40 using lower quality base oils than it is to make a 0/5w-30 with a minimum HTHS of 3.5 out of higher quality base oils since the prices in Europe seem to reflect that.
 
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I know two people who have used Xw20 oils long term in VW's both with bad results. Namely timing chain sprockets and cam lobes failing. I would think with as large as VW is, they intentionally design their cars to run on specific oils which happen to be thicker. They do appear to be in the stone age of lubrication. The one vehicle was a Jetta I4 and the other was a GTI VR6. They both took their cars to shops / oil change places that were unaware of 502 505 specs. The damage that occurred is similar to this link I found. Click here
 
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