When is the best time to do a UOA?

[demarpaint]

In my quest to learn, I read UOA reports and see it is actually pretty easy to skew a report, screw one up, or end up with useless info. Sometimes that is, at least IMO.

My questions and observations:

I've read reports where the person taking the sample was questioned about how long the engine was running when the sample was taken because of high fuel levels, or moisture/water contamination. IMO if you are doing a UOA, and the car is driven for only 10 minutes at a time, then the sample should be taken after the engine is driven 10 minutes. In this example even our favorite oils might not look so good, but it would accurately show the condition of the oil, which represents exactly how the car is driven. If the car is driven for an hour, then the sample should taken after an hour on time. Only then IMO are you actually getting an accurate report, that's if the lab doesn't [censored] it up!

Then I thought maybe the sample should be taken at 5 minutes and 30 minutes in both examples. My reason is it takes time for the engine to get warmed up so in reality the car driven 10 minutes is really taking a hit. So maybe half the time might be a better representation? Running an engine an hour that only sees two 10 minute trips a day certainly isn't going to give an accurate report? Or is it?

Thanks

 

[INDYMAC]

Take the sample after you've driven it like you usually do. If you don't have a routine, then it doesn't matter. You are looking for average condition of the oil. So if there are problems with your engine tune or driving style, they will be more apparent. Then you can make appropriate corrections that might be available to you.

 

[demarpaint]

Thanks INDY, so I guess I'm barking up the right tree. I wonder how many people driving cars 10 minutes each way go for a long drive, then drop their oil and collect a sample? In the meantime they could have moisture and fuel dilution problems not showing up, and in reality should be changing their oil sooner. They could be driving around with a false sense of security?

 

[Shuttler]

The best time is right before morning dew.

 

[Eddie]

My usual days first run is 3 miles to a Café for breakfast and then back home. That is when I drain the oil and take the sample. That way I get a representative sample and not a skewed sample.

 

[demarpaint]

Originally Posted By: Eddie
My usual days first run is 3 miles to a Café for breakfast and then back home. That is when I drain the oil and take the sample. That way I get a representative sample and not a skewed sample.


If that's how the car is driven then that's how I'd take the sample.

 

[Patman]

You definitely raise a good point, however I'd be willing to bet that most of the people here on BITOG are picky enough that they would make it a point to drive their cars on a longer drive at least once a week if their normal daily commute is a short one and they know they aren't normally getting the oil good and hot.

Like my wife's car for instance. Her trip to work is only about 8 miles each way, so the oil probably just barely reaches operating temperature when she gets to work in the colder months. But on the weekends I always make it a point to take the car for a good drive and get the oil good and hot.

 

[demarpaint]

Based on that when would you draw a sample? During the week when the oil is in its most normally used condition, or after the long weekend run when the oil would be at its best?

My intent is not to poke the hive. I want to get an idea of what would give the most bang for the buck, and most accurate UOA report based on how the vehicle is normally operated. Or draw a sample when fuel and condensation is burnt off, which for some of use might only be one or two days out of a week.

 

[Doug Hillary]

Hi,
demarpaint - I have always set two basic criteria in drawing a lubricant sample;

a) the lubricant must have a temperature of at least 60C

b) the engine must not have been stopped for longer than 10 minutes

Others may have other ideas!

 

[demarpaint]

Thanks for the reply Doug!

 

[Gary Allan]

Quote:
Running an engine an hour that only sees two 10 minute trips a day certainly isn't going to give an accurate report? Or is it?


I don't think you'll miss anything. If you remove the fuel and/or moisture, the elements will be the same ..the TBN will still be tanked (if it is) ..etc..etc. You can't undo what's been done. If the fuel was high, you might flash half of it off with a long drive, but allegedly about half of the components will form residuals that are supposed to be stubborn. You'll still show the effects. Your insoluble level isn't going to be reduced.

 

[demarpaint]

Thanks Gary, I thouht most fuel and mositure would be burnt off after an hour. So less would show in the UOA than would show if the engine was only run for 10 minutes. I thought that might trigger an inaccurate reading based on how the car is actually used.

 

[Gary Allan]

Well, yeah. But you can't mask the effects. I guess it would be easier to see why you have the oil in the condition you do.

Some labs cannot tolerate moisture. Their machinery gets fouled. B-S and most others are cool with it, but Cat-Butler does some pre-testing (probably a crackle test) and won't give you all the results. I forget what they won't do since it's been years. Our inside man, Mark Matheys (spl) aka Stinky Peterson, died in a trailer accident (got run over by his log splitter). Terry was hooked up with him and they didn't run a test due to the moisture.

 

[21Rouge]

Originally Posted By: Doug Hillary
b) the engine must not have been stopped for longer than 10 minutes


And yet didnt I read in this thread or maybe another that one 'should' draw a sample at the point when one can comfortably handle the dipstick....that would be (much) longer than 10 minutes after a longer drive.

 

[21Rouge]

Originally Posted By: Gary Allan
You can't undo what's been done. If the fuel was high, you might flash half of it off with a long drive, but allegedly about half of the components will form residuals that are supposed to be stubborn. You'll still show the effects.


+1.

If one has ongoing fuel dilution the a long drive prior to sampling may burn off existing fuel in the oil but flashpoint and viscosity #s will tell the tell of previous and consistent fuel in the oil.