UOA for used vehicle evaluation
- Thread starter mek42
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Yes and No, IMO a good scanning and compression test can tell you more in a shorter amount of time. Realize if you send a sample to say blackstone your looking at about 3-5 days for results. The vehicle could be sold while you dilly-dally around with it.
Without a trend a used oil analysis is worthless, unless your looking for fuel or coolant in the sample.
By the way
to BITOG
Without a trend a used oil analysis is worthless, unless your looking for fuel or coolant in the sample.
By the way
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"Without a trend a used oil analysis is worthless, unless your looking for fuel or coolant in the sample."
+1. Plus the turnaround time.
+1. Plus the turnaround time.
Agree with Dieseltech for the most part, although you could potentially spot other problems. F.e. if you had high lead or something. I would rely on maintenance history, and pre-purchase inspection much more than a used oil analysis. but for the cost of $25 or so, it does give you one more piece of info.
dnewton3
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I agree that you won't really be able to discern wear trends.
However, coolant, water, dirt intrusion, or other really high wear metals could tell you something. Also, presuming the oil is of the sellers choice, you can learn of what has not been done right, moreso that what was done. For example, if the vis is WAY out of range (high or low) for what the seller claims, it's likely that he/she is either uninformed,lazy or lying; none are complimentary and would make me question any maintenace statements they claim. If the vis is way high, perhaps they added a thickener to stop leaks. Or if way low, perhaps they ran the oil for way too long and it's sheared badly, indicating poor maintenance practices. The list goes on and on. You can learn much from a used oil analysis that has nothing to do with wear.
Pulling a valve cover can tell you a lot visually as well. Typically, at least one is easy to get off for a quick check.
However, coolant, water, dirt intrusion, or other really high wear metals could tell you something. Also, presuming the oil is of the sellers choice, you can learn of what has not been done right, moreso that what was done. For example, if the vis is WAY out of range (high or low) for what the seller claims, it's likely that he/she is either uninformed,lazy or lying; none are complimentary and would make me question any maintenace statements they claim. If the vis is way high, perhaps they added a thickener to stop leaks. Or if way low, perhaps they ran the oil for way too long and it's sheared badly, indicating poor maintenance practices. The list goes on and on. You can learn much from a used oil analysis that has nothing to do with wear.
Pulling a valve cover can tell you a lot visually as well. Typically, at least one is easy to get off for a quick check.
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used oil analysis are not of much value since each company can vary with the results quite a bit with the same oil. However with a used car eval it would be helpful to detect coolant as already been mentioned. This might really be helpful if you were buying a GM V6 which has a history of coolant contamination in the oil.
The only reason I would consider a used oil analysis as part of a pre-buying evaluation would be if the vehicle was one known to commonly leak coolant into the oil. Any DexCool filled GM with the known lower intake gasket problem would be a good reason to do a used oil analysis. A model year 2000 Jeep 4.0 with the "331" head casting prone to cracking would be another. I'm sure there are many.
In the case of the Jeep, say the car has 100,000 miles and a 331 casting. If it hasn't cracked, odds are VERY good that it never will in 300,000 miles- if they fail, they usually fail before 100k. But at 100k, it could be leaking just enough for a used oil analysis to find it, but not enough to show obvious oil contamination. Its a good screening test in that case. If it shows no contamination, buy with a better degree of confidence.
But for wear metals- forget it. As others have said, without a trend a used oil analysis doesn't mean a lot, and on top of that an engine can be grinding itself apart producing large wear particles that a normal used oil analysis wouldn't detect.
In the case of the Jeep, say the car has 100,000 miles and a 331 casting. If it hasn't cracked, odds are VERY good that it never will in 300,000 miles- if they fail, they usually fail before 100k. But at 100k, it could be leaking just enough for a used oil analysis to find it, but not enough to show obvious oil contamination. Its a good screening test in that case. If it shows no contamination, buy with a better degree of confidence.
But for wear metals- forget it. As others have said, without a trend a used oil analysis doesn't mean a lot, and on top of that an engine can be grinding itself apart producing large wear particles that a normal used oil analysis wouldn't detect.
Also, would you really know for sure what oil type and viscosity was in the engine ?
Probably not, nor the miliage on the oil either.
And as mechanicx said, most used car dealers change the oil before putting it on the lot anyhow.
Good luck.
Probably not, nor the miliage on the oil either.
And as mechanicx said, most used car dealers change the oil before putting it on the lot anyhow.
Good luck.
When I was first reading of used oil analysis, it sounded like a good idea...but yea, a bad UOA is easy to avoid; simply by changing the oil. For example, I've heard of many craigslist car salesman change the oil before a sale....since obviously if people see golden oil they are gonna think it's been well-kept.
My sister was looking at a car one of these doof's was selling, he even went as far as telling her he's changed the oil 3x in the past 2 weeks...well, for WHAT? Must have been a reason for the un-necessary changing
But she didn't have the knowledge she has now (from me, and my father) to question further. Luckily she didn't buy it 
My sister was looking at a car one of these doof's was selling, he even went as far as telling her he's changed the oil 3x in the past 2 weeks...well, for WHAT? Must have been a reason for the un-necessary changing
Send it overnight mail. If the car has ever been flooded the UOA will pick it up. Do the Trans and differential too if it is rear wheel or 4wd. Flooded cars is a big problem here and even if they changed the oil it will pick it up.
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