Why warm up oil before a UOA sample is taken?

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My UOA kit from OAI/Amsoil is supposed to arrive this weekend. Now I'm thinking about the process. Blackstone says when sampling, "Getting the oil up to operating temperature should help cook out any moisture or fuel build-up from the last time you drove."

Why should anyone do this? Wouldn't it be better to know if there is fuel in the oil? I'd call Blackstone but I'm getting my uoa from OAI/Amsoil. I saw one or two threads on this, but don't recall a conclusive answer. I do recall someone saying in a thread I read, something about doing this would replicate normal driving conditions, but I would think that if there is normally fuel in the oil, one should know about it--if it is getting burned off, then one would think it would not cause additional wear, but still one should know that it is there in the oil.

Thoughts?
 
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Let me ask you, which chapter of the Motor Oil University deals with the best temperature for oil to take a sample for a UOA?

Originally Posted by Imp4
Read the motor oil university section of BITOG.
 
I took a sample from my mazda DI that was right after my wifes 7 mile commute, this was in cold weather, and there was a lot of fuel dilution. I wanted to see how much fuel dilution there was after her short trip.

That way i know what her typical drives do to the oil.
 
Originally Posted by spasm3
I took a sample from my mazda DI that was right after my wifes 7 mile commute, this was in cold weather, and there was a lot of fuel dilution. I wanted to see how much fuel dilution there was after her short trip.

That way i know what her typical drives do to the oil.


IMO that's the right way to do it. If the car is driven on short trips take a sample after a short trip. If driven on a long trip take a sample after a long trip. That would yield results based on how the vehicle is used. No point in taking a vehicle that is only driven on short trips for an hour drive and sample the oil, that wouldn't be a fair representation of how the vehicle is used, and might skew the results.

When I take an oil sample from my van I drive it for about 2-3 miles, that's pretty much how it is used. My other vehicles are typically driven at least 30-90 minutes, so I would sample the oil after about a 30 minute drive. I feel that is long enough, and anything after that is a moot point.
 
I think what you are Demar are saying makes a lot of sense.

I get the idea of not wanting to merely collect what has gathered at the bottom of the oil pan--a drive of course would mix it up, but I don't plan on taking it for a 30 minute drive, as most of the time the vehicles get driven 20 mins, some of that city streets.

Originally Posted by spasm3
I took a sample from my mazda DI that was right after my wifes 7 mile commute, this was in cold weather, and there was a lot of fuel dilution. I wanted to see how much fuel dilution there was after her short trip.

That way i know what her typical drives do to the oil.
 
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I did one Blackstone oil analysis on a Saturn with a 1.9. I only drove it a few miles and it did show fuel dilution. Blackstone was not sure if it was due to oil not being warmed up and put a comment to that effect on what they wrote. I think if they give verbal feedback on your sample I would tell them how long car was warmed up before sample is pulled.
 
Originally Posted by paulri
I think what you are Demar are saying makes a lot of sense.

I get the idea of not wanting to merely collect what has gathered at the bottom of the oil pan--a drive of course would mix it up, but I don't plan on taking it for a 30 minute drive, as most of the time the vehicles get driven 20 mins, some of that city streets.

Originally Posted by spasm3
I took a sample from my mazda DI that was right after my wifes 7 mile commute, this was in cold weather, and there was a lot of fuel dilution. I wanted to see how much fuel dilution there was after her short trip.

That way i know what her typical drives do to the oil.


I recall having a conversation with someone very knowledgeable about the topic and that was the advice I was given. I also believe a few years back this was discussed here, and some of the resident experts concurred. It made sense to me, so that is what I've been doing. I was surprised with my van to see fuel dilution and water were not issues. With such short runs I would surely have bet those items might have been something flagged. The longer driven vehicles were fine too with regard to water and fuel.
 
It is fine to take a cold sample in the sense that you park the vehicle when you get home from work one day and then you go out the next day and change the oil WITHOUT starting the engine...but if you start the engine to drive it up on stands etc in order to change the oil, your sample will likely show fuel as most engines run rich until they go into closed loop operation (reach full temp)
 
Which would then give you a higher than normal fuel reading (starting the engine to drive it up on ramps). So that is why a normal drive, whatever your car normally does, would be a good approach--to burn off whatever fuel normally gets burned off, but no more. This of course does not mean a 20-30 min freeway run, to bring fuel down to 0. You made a good point there.

Originally Posted by thastinger
It is fine to take a cold sample in the sense that you park the vehicle when you get home from work one day and then you go out the next day and change the oil WITHOUT starting the engine...but if you start the engine to drive it up on stands etc in order to change the oil, your sample will likely show fuel as most engines run rich until they go into closed loop operation (reach full temp)
 
Closed loop is where samples are taken on some industrial engines … like a sample valve in a cooler line while the engine is at operational temps and use. (Guru does not want sump sample)
To emulate that on a street vehicle?
I'd only do it if I ever had an Amsoil dual filter and Amsoil SS thing going that requires UOA.
Me? I just apply my UOA saving to a jug of oil … and thanks to those who do post since I learn from those.
 
The only "benchmark" to see how your engine is doing compared to others is to have the same "controlled" circumstances in how and when the sample is taken and that is to do a "full operating" temperature oil sample.

Now if you just curious on what is going on in your engine under the short trips your vehicle makes that is fine, you are then just curious about fuel dilution and honestly makes sense for those who wish to do it however, once you get the results and its full of fuel etc, don't start looking for advice or wasting money on parts, thinking something is wrong with the engine. Because you have no idea if something is.

With a full hot oil sample, your getting true viscosity readings, wear metals and if excess gas in getting into the oil once the engine is up to full operating temperature.
You see, there has to be a benchmark/baseline and that would be once the engine is warmed up.
 
Interesting. I just went to the OAI website, and found this about sampling conditions:

Fluid analysis is most effective when samples are representative of typical operating conditions. Dirt, system debris, water and light fuels tend to separate from lubricants and coolants when system temperatures cool. For optimum results:• TAKE SAMPLES WHILE SYSTEMS ARE OPERATING UNDER NORMAL CONDITIONS or immediately after shutdown while they are still at operating temperature

Well that right there gives a reason why they (along with BS) want you to take it when engine is hot. Making sure dirt & other contaminants are uniformly circulating throughout all the oil, hence will be represented in your sample, is a very good reason. Only problem is that like I said above, I don't want to burn off fuel if it is there in short trips, but not in long trips.

No, I had no intention of trying to track down a "fuel in the oil problem" and start repairing a problem that doesn't necessarily exist. I just want to see if there is fuel. Coolant can be identified by sodium & potassium, even if the water has burnt off.


Originally Posted by alarmguy
The only "benchmark" to see how your engine is doing compared to others is to have the same "controlled" circumstances in how and when the sample is taken and that is to do a "full operating" temperature oil sample.
...With a full hot oil sample, your getting true viscosity readings, wear metals and if excess gas in getting into the oil once the engine is up to full operating temperature.
You see, there has to be a benchmark/baseline and that would be once the engine is warmed up.
 
FWIW, I ended up driving 8 miles round trip to warm the oil up just a bit; I saw by the time I reached my halfway point that the needle for the temperature had already risen to the halfway mark (although people here have said that this means it has just reached a range, and does not necessarily mean that the oil is a certain temp). Took the sample; unfortunately I have to wait till Monday to mail it in.
 
I take my oil sample after my normal daily drive. I don't want to skew the results with bad untypical data by taking a long drive. If my daily drive is 2 miles and back to work, that's when I take the sample.. Ed
 
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I would prefer to see the results both taken from after my drive home from work (a few miles each way) and after a half an hour drive to see how quickly the fuel dilution drops. My commute is way too short and both my summer and winter car are carbureted.
 
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