Owner's Manual Oil Checking Instructions? Confusion

[ClassaxV]

As long as I have owned cars I have been diligent about checking my oil. My first car was an RX7 so it was a necessity. I know that every vehicle has an optimum procedure for checking the levels and getting the correct reading. However the information in the owner's manual for the CT4 has me a bit confused about how to check the level.

"Follow these guidelines: . To get an accurate reading, park the vehicle on level ground. Check the engine oil level after the engine has been off for at least two hours. Checking the engine oil level on steep grades or too soon after engine shutoff can result in incorrect readings. Accuracy improves when checking a cold engine prior to starting. Remove the dipstick and check the level. . If unable to wait two hours, the engine must be off for at least 15 minutes if the engine is warm, or at least 30 minutes if the engine is not warm. Pull out the dipstick, wipe it with a clean paper towel or cloth, then push it back in all the way. Remove it again, keeping the tip down, and check the level."

It's the last statement "must be off for at least 15 minutes if the engine is warm, or at least 30 minutes if the engine is not warm." I assume this is based on the first instructions that the best readings are gotten when the oil is cold and drained to where it settled. But then the statement above seems like it would be reversed. It would seem like one would need to wait LONGER if the engine is warm (come up to operating temp I assume) vs when it is still cold unless there is evidence that it takes the cooler oil longer to settle to readable levels. It's just strange. Thoughts....?

 

[Sticker Boy]

Like tires, I check it cold after it’s been sitting in the garage overnight for the most accurate reading.

 

[565565]

As long as I have owned cars I have been diligent about checking my oil. My first car was an RX7 so it was a necessity. I know that every vehicle has an optimum procedure for checking the levels and getting the correct reading. However the information in the owner's manual for the CT4 has me a bit confused about how to check the level.

"Follow these guidelines: . To get an accurate reading, park the vehicle on level ground. Check the engine oil level after the engine has been off for at least two hours. Checking the engine oil level on steep grades or too soon after engine shutoff can result in incorrect readings. Accuracy improves when checking a cold engine prior to starting. Remove the dipstick and check the level. . If unable to wait two hours, the engine must be off for at least 15 minutes if the engine is warm, or at least 30 minutes if the engine is not warm. Pull out the dipstick, wipe it with a clean paper towel or cloth, then push it back in all the way. Remove it again, keeping the tip down, and check the level."

It's the last statement "must be off for at least 15 minutes if the engine is warm, or at least 30 minutes if the engine is not warm." I assume this is based on the first instructions that the best readings are gotten when the oil is cold and drained to where it settled. But then the statement above seems like it would be reversed. It would seem like one would need to wait LONGER if the engine is warm (come up to operating temp I assume) vs when it is still cold unless there is evidence that it takes the cooler oil longer to settle to readable levels. It's just strange. Thoughts....?

It makes sense. When you run the engine the oil gets pumped up into the block. When you turn it off it settles back into the pan. Warmer oil is less viscous and settles faster than colder oil.

So basically if you cold start the car and shut it off immediately and check the oil, your readings will be artificially low.

 

[GTANotch88]

I think the 15/30 min thing is correct...
If you drive the car an hour, oil is warm and will return to the pan quicker than cold oil. But say you just start the car, doesn't get to warm up really, now the still fairly cold oil has been pumped up into the engine and will take more time to flow back down. At least that's one way the manual can be interpreted.

 

[ClassaxV]

I fully understand the concepts and it's very true for the heavy oils we used to use, but modern oils are so much thinner and the viscosity don't vary from cold to warm like the old days.

The manual is accurately worded but not eloquently so.

 

[M2Cto4BW]

I think the 15/30 min thing is correct...
If you drive the car an hour, oil is warm and will return to the pan quicker than cold oil. But say you just start the car, doesn't get to warm up really, now the still fairly cold oil has been pumped up into the engine and will take more time to flow back down. At least that's one way the manual can be interpreted.

Yup - whether really necessary or not that is definitely the intent of the message. They could have cleaned up pretty easily say...
For an accurate reading check your oil after the engine has been shut off for 2 or more hours. If you cannot wait 2 hours, do the following based on whether you engine was fully warmed up or not:
- wait at least 30 mins if your engine reached nn F/C or higher
- wait at least 15 mins if your engine reached nn F/C or less