Sometimes a cold sample is better.

[RamFan]

Question-
I will soon be conducting a used oil analysis on an '08 Sebring 2.7l V6. This vehicle is used only for short trips, less than 5 miles daily. When I take my sample should I still take the car out long enough to boil off moisture or should I take the sample cold? Since the engine never gets to operating temp taking it cold should reveal what exactly the oil looks like as it is being pumped through the engine, whereas taking it hot may give a "false-positive" of the oils condition. What would you suggest?

Blackstone Answer-
Thanks for the e-mail. Since your engine doesn't see much highway use, it may indeed be a little deceiving to get a sample after a long run on the highway. Go ahead and get one from a cold engine after normal operation and lets see what shows up. Things might not be bad at all.

 

[The motor guy]

The only thing that would give a false positive by running it down the freeway would be that any excess fuel/moisture from the short trips would be gone. And it would give a false positive on the viscosity.

 

[RamFan]

Originally Posted By: motor_oil_madman
The only thing that would give a false positive by running it down the freeway would be that any excess fuel/moisture from the short trips would be gone. And it would give a false positive on the viscosity.


Exactly right. Since the engine never gets up to operating temperature I'd like to see how much fuel and moisture is in the oil while it is being run, rather then burn it off going on a drive that the vehicle never sees under normal operating conditions.

 

[friendly_jacek]

Originally Posted By: motor_oil_madman
The only thing that would give a false positive by running it down the freeway would be that any excess fuel/moisture from the short trips would be gone. And it would give a false positive on the viscosity.


I would call it false negative.

 

[ltslimjim]

Definitely take a sample cold in your case, or just after one of your short trips, to make it look the worst.