Can a good UOA be misleading?

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43
Location
The Gawden State
Hello, I have been reading these forums for almost a year, daily, and this is my first post because you guys answer all of my questions before I ask them. The oil obsession bug has bitten me. I feel like I know you all, and when my wife's friends complain about spousal internet porn addiction she tells them this is worse because I make her sit with me. Whoa!Too much sharing,sorry My question has to do with viscosity and wear, specifically if using a thicker or thinner oil than recomended can result in shortened engine life despite good UOAs. Could there be a problem that doesn't show in these tests? My car is a Passat 1.8T, and there have been many exellent reports with both 5W30 and 0W/5W40 oils for this engine. This year VW sent out a TSB recomending 5W/10W40 for fill, and 5W30 for top off only. Is it reasonable to think a 5W30 with a good analysis is bad for my car? Am I overthinking this, is it nothing? I have 5W30 ASL in it right now. Joe I thought I knew, But I had no idea - The Pebble
 
Messages
168
Location
KY
quote:
Originally posted by mirou: Hello, I have been reading these forums for almost a year, daily, and this is my first post because you guys answer all of my questions before I ask them. The oil obsession bug has bitten me. I feel like I know you all, and when my wife's friends complain about spousal internet porn addiction she tells them this is worse because I make her sit with me. Whoa!Too much sharing,sorry My question has to do with viscosity and wear, specifically if using a thicker or thinner oil than recomended can result in shortened engine life despite good UOAs. Could there be a problem that doesn't show in these tests? My car is a Passat 1.8T, and there have been many exellent reports with both 5W30 and 0W/5W40 oils for this engine. This year VW sent out a TSB recomending 5W/10W40 for fill, and 5W30 for top off only. Is it reasonable to think a 5W30 with a good analysis is bad for my car? Am I overthinking this, is it nothing? I have 5W30 ASL in it right now. Joe I thought I knew, But I had no idea - The Pebble
What's a UOA? Sorry!
 
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18,449
Location
East of IGO
In all honesty this is my opinion and others may give you different answers. An analysis gives a general overview on the oils condition and a simple look at the engine. to get the most complete goings on by an oil sample a partical count is the best as the typical analysis posted in the forums measures stuff under 4 microns .I hope someone with more expertise on this subject posts.
 
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373
Location
Port Colborne, ON
quote:
Originally posted by Justin:
quote:
Originally posted by mirou: Hello, I have been reading these forums for almost a year, daily, and this is my first post because you guys answer all of my questions before I ask them. The oil obsession bug has bitten me. I feel like I know you all, and when my wife's friends complain about spousal internet porn addiction she tells them this is worse because I make her sit with me. Whoa!Too much sharing,sorry My question has to do with viscosity and wear, specifically if using a thicker or thinner oil than recomended can result in shortened engine life despite good UOAs. Could there be a problem that doesn't show in these tests? My car is a Passat 1.8T, and there have been many exellent reports with both 5W30 and 0W/5W40 oils for this engine. This year VW sent out a TSB recomending 5W/10W40 for fill, and 5W30 for top off only. Is it reasonable to think a 5W30 with a good analysis is bad for my car? Am I overthinking this, is it nothing? I have 5W30 ASL in it right now. Joe I thought I knew, But I had no idea - The Pebble
What's a UOA? Sorry!

used oil analysis
 
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47,638
Location
Duvall WA - Pacific NW USA
If the 5W-30 is giving you good results don't sweat it. ASL is a good oil. I just went 20K miles in the wife's Volvo 850 (non-turbo)and while the oil thinned a bit, and the TBN was a tad low, the wear was almost nothing. Since you have a turbo don't go longer than 6 months. Not sure why VW is suddenly recommending xW-40 but maybe wait until spring or the early summer and switch, but again don't worry.
 
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3,845
Mirou, UOA can be misleading if it is not interpreted correctly. Meaning the analyst needs to understand the test protocals, oils, engine, and finally you. Very few if any labs have the time on a test for less than $100 to perform that kind of service. If your analysis results are in the normal range, the lab is accurate, there is little to slip by and cause a problem as it can be seen early on if properly interpreted and caught before it becomes catastrophic. As far choosing a vis and your specific engine, I say the analysis is more relevant to controlling engine wear than a TSB put out from wolfsburg to cover all the morons out there that could car less about good maintenance. Let the analysis results guide you not a blanket statement used to CYA corporate warranty issues.
 

mirou

Thread starter
Messages
43
Location
The Gawden State
Thanks for taking the time to answer my questions. Only 368 more to go. Now I'll be able to sleep. ( for tonight) Next topic --Trending. JOe The measure of a man is more than just cm. - anon
 
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40,143
Location
Great Lakes
quote:
Originally posted by mirou: Hello, This year VW sent out a TSB recomending 5W/10W40 for fill, and 5W30 for top off onlyJoe
What TSB? I'm not aware of one. Can you provide a link possibly? The owner's manual of my A4 1.8T calls for 0w-30 and I haven't seen any changes to this literature. Nevertheless, I use 0w-40 (synth), and if I go to the dealer for the free oil change, they'll put in some mineral 15w-40 because that's all they have and that's what they use for all Audis they service, regardless of year or engine type. [Dummy!]
 

mirou

Thread starter
Messages
43
Location
The Gawden State
Pete, I saw it on clubb5 about 6 months ago. I tried to find it so I could link to it in my original post but, no luck. I think they released it when they changed the 2003 manual recomendations. I'll ask someone to repost it. joe
 
Messages
500
Location
Vermont
Mirou, I think the following is at least partial answer to your question. The typical UOA we see here on the forums is a spectrographic (correct me if I'm wrong) analysis of the oil. What I read at the site of a lab that does these is that they are only able to detect very very small particle sizes using this method. The example they gave as to why this could be a problem is this; a big iron ball bearing sitting in your oil sample would give a spectrographic reading of 0. It's just not designed to find particles bigger than a certain (I don't know exactly) size. So the answer is yes, a UOA can be misleading in that you could have low wear numbers but a catastrophic failure could be imminent. But, these analyses are definitely worth doing, I do them at every change.
 
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