VW 502.00 and HTHS minimum

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23,591
It's been mentioned that the VW 502 spec requires very demanding high temp/high load testing in a test that runs for 248 hours during which no makeup oil is allowed. What I would like to know is whether or not the minimum HTHS of 3.5 must be maintained until the end of this test or until the end of the suggested end of the drain interval for any particular VW/Audi vehicle. If in fact, the HTHS may be lower than 3.5 during or after the test, then a safety margin must have been taken in account, and it would be good to know what the actual minumum HTHS figure is. My question is, must the minimum HTHS of 3.5 be maintained during the above-mentioned test or during the entire drain interval in order to make this oil eligible for VW 502.00 approval? If the answer is yes, then how did M1 0W-40 get approved, since it reportedly thins out a lot. If the HTHS of 3.5 is only required at the beginning of the test, then this figure seems pretty meaningless.
 
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quote:
Originally posted by moribundman: It's been mentioned that the VW 502 spec requires very demanding high temp/high load testing in a test that runs for 248 hours during which no makeup oil is allowed. What I would like to know is whether or not the minimum HTHS of 3.5 must be maintained until the end of this test or until the end of the suggested end of the drain interval for any particular VW/Audi vehicle. If in fact, the HTHS may be lower than 3.5 during or after the test, then a safety margin must have been taken in account, and it would be good to know what the actual minumum HTHS figure is. My question is, must the minimum HTHS of 3.5 be maintained during the above-mentioned test or during the entire drain interval in order to make this oil eligible for VW 502.00 approval? If the answer is yes, then how did M1 0W-40 get approved, since it reportedly thins out a lot. If the HTHS of 3.5 is only required at the beginning of the test, then this figure seems pretty meaningless.
I wish i knew the answer [Smile] , Why don't you send this q in some euro oil companies? At least one of them should give you some answer ..although i wouldn't expect any details.
 

moribundman

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I'm curious too, but I don't want to go on a wild goose chase. [Wink] I figured someone here might know the answer. I think Primus mentioned once that an oil must maintain the required minimum HTHS throughout the whole test.
 
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As Ted has said, there is no requirement that the HT/HS viscosity be maintained throughout the test. I feel that this is one reason that the HT/HS is set at >3.5 - to allow for thinning without passing the borderline safe limit of 2.6.
 
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The high temp, VW "T-4" test, which is part of the VW 502 spec, limits the viscosity INCREASE due to oxidative thickening after 248 hrs. I believe the test allows for an 80% increase in the viscosity @ 40C - that's from memory, so I may be off slightly. There is NO requirement that HT/HS viscosity be maintained. The generic, ACEA "A3/B4" tests require that the oil "stay in grade" after 30 flow cycles. So the viscosity of the Mobil 1, 0w-40 would have to be 12.5 Cst or better when tested @ 100C under a low shear rate. This test uses a Bosch fuel injector to rapidly shear the oil, by forcing it through a small orifice under high pressure. However,since the Bosch test is done at ambient oil temps, it does not analog the combined mechanical shearing AND thermal degradation you find in an actual engine. Tooslick
 
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To be correct I wrote in our August 03 discussion on Mobil1 OW-40 HT/HS: "... Making approval for use of this or that oil in their cars manufactures expect that this oil will keep HT/HS > 3.50 during all prescribed oil interval. ... Bosch injector test is used 1. for "stay in grade" qualification, 2. as reference point for oil comparison within the same method. Tests define % loss of kinematic viscosity at 100 deg C, but not loss of HT/HS viscosity measured at 150 C ..." Moribundman asked very important question. That's why I have tried to clarify this issue at our certification lab and got the following answer: 1. Naturally HT/HS will decrease if the oil thins out. But HT/HS change is not always being direct. Nature of base stock will have an impact on actual HT/HS in given conditions. 2. Oil approved for a long drain interval should ensure engine protection through the whole interval under the normal conditions. OEM tests suppose the engine is fully OK, i.e. does not have a noticable wear and its fuel system work as per OEM specs, i.e. these tests are run on new cars or like new. It's expected that under normal conditions the oil in such engine will not suffer some considerable loss of kinematic viscosity. A temporary viscosity loss may occure at certain conditions, but given it happens during a short period of time this usually does not cause the engine failure, though it does not promote a long engine life too. 3. "Stop and go" cycle, sustained high speed driving etc. don't fall under "normal" conditions where OEMs' recommendations of shorter intervals. Oil thinning may bring HT/HS lower then 3.50. But again, it may lead to a higher engine wear, but it will not be mortal. Firstly, it's expected that if the owner follows prescribed intervals for severe conditions, a thinned oil could be in the crankcase for a short period only. Secondly, an additive chemistry will protect your engine too. 3. OEM recommendations for oil quality, viscosity and drain interval take into consideration all possible conditions. So, recommending an oil OEM leaves a safety margin, but it have to be clear that here the main and only target is to allow its engine to survive, especially if the car is still under the warranty. 4. VW 502.00 does not specify an additional requirement to ACEA test in respect of viscosity loss (Bosch injector). In the part of viscosity control the test PV1449 stipulates two parameters: initial viscosity at 40 C and its relative increase caused by oxidation. Everybody may make his own conclusion. I understand that Audi/VW had probably some strong reasons to stipulate 5W-30, 5W-40, 10W-30 and 10W-40 for + 15 C only in their 501.01 and 505.00 norms. So, irrespective whether or not their original 5W-40 oil is a real synthetic, for safety reasons it probably would have sense to go one grade up or to shorten drain intervals.
 
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