Why not take oil sample from oil drain catch pan?

Messages
1,027
Location
East Helena, Montana
I know that the recommended procedure is to fill the UOA bottle during about the middle of the flow as the oil flows out of the drain plug hole. However, this is obviously going to be at least a bit messy. I've been wondering. Why not just dip the bottle into the oil in the drain pan after all the oil's drained out? Seems to me that would give you a representative sample of the drained oil?
 

GMZ

Messages
297
Location
PNW
I just did my very first UOA I filled the bottle as the oil was draining into the pan. Was very easy and not messy at all. Didnt even need gloves. If you dipped the bottle into the pan wouldnt you make more of mess? I should have taken some pics when I did mine. My car was on a lift though.
 
Messages
1,088
Location
Baltimore, MD
If your pan is clean, go ahead. My pan is pretty dirty with residue from previous oil changes, bits of leaves and dirt that blow in it while the oil is draining.
 
Messages
4,478
Location
Southern California
Do whatever floats your boat, but I believe the possibility of disproportionate contamination is the issue as Blackstone and kanling have both indicated. Early stream sampling introduces the possibility of crud at the drain impacting the contaminants count - especially silicon. By midstream, dirt at the drain hole has likely been rinsed clear by the first part of the stream. The final part of the stream might introduce unrepresentative amounts of pan-bottom crud swept by the last of the flow into the sample. I haven't seen any studies proving all of the above are a <i>real</i> concern, but using a little sampling common sense can't hurt. I haven't seen any studies that an asteroid collision with earth will wipe all life off the face of this planet, but I see no reason to invite such an event to test current theories, either.
 
Messages
1,550
Location
North Texas
My drain pan gets thoroughly cleaned after each oil change. WIped out with apper towels, then i use windex to completely remove all the oil and grease from it. Then again, i'm weird:P
 
Messages
6,171
Location
Santa Barbara, CA
Ray H it would be interesting for someone to take 3 samples from one drain: early, mid, late stream and send it in for a comparison. Would have to be a large sump or someone with three hands. Be easy if you have a full lift, I guess. edit: a fourth sample could come from the drain pan for even more comparison fun. Assign random numbers to the samples so the last cannot be biased at all. Someone DO IT! [Cheers!] FOR BITOG! [Cheers!]
 
Messages
1,412
Location
Falls Church VA
Father of one of my dealers got a call from the lab, telling him that he had antifreeze in the oil. He was very puzzled, since he had seen no evidence in the oil, and had not added coolant. Since he had run the fresh oil for about 1500 miles, he pulled another sample and sent it off. This sample was fine. He scratched his head, and tried to figure it out. AHA! Previous fall, he had drained his old antifreeze into a large pan when changing it. He then washed out the pan, and put it in the garage. Sure enough, when he changed the oil, he used the same pan. Then he dipped out a sample. Doesn't take much to contaminate the sample.
 
Messages
12,385
Location
Northern CA
quote:
Originally posted by Dick in Falls Church: He scratched his head, and tried to figure it out. AHA! Previous fall, he had drained his old antifreeze into a large pan when changing it. He then washed out the pan, and put it in the garage. Sure enough, when he changed the oil, he used the same pan. Then he dipped out a sample. Doesn't take much to contaminate the sample.
That's not surprising. There are roughly 50,000 drops per gallon, depending on the definition of "drop". There is about 1 gallon of used oil in a change. That means that 1 drop in a gallon would be about 20 ppm. That gives me even more appreciation of the detailed level of measurments I get in my $20 UOA.
 
Messages
956
Location
Eastern burbs, MN
I use a clean "Ratio Rite" measuring cup to capture my oil samples mid-stream then transfer the oil to the Blackstone container. I make absolutely sure the cup is clean before I take a sample. So far so good.
 
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