Hello. Can someone please explain why the Owner's Manual says we need to let the engine warm up to check the engine oil level ?

In step 3 below, we wait for the oil to return to the oil pan before looking at the dipstick, so why might that give a different result than checking the oil level when the engine is cold and all the oil is already sitting in the oil pan ?

From page 8-10 Owner's Manual:
"Inspecting Engine Oil Level
-------------------------------
1. Be sure the vehicle is on a level surface.
2. Warm up the engine to normal operating temperature.
3. Turn it off and wait 5 minutes for the oil to return to the oil pan.
4. Pull out the dipstick, wipe it clean, and reinsert it fully.
5. Pull it out again and examine the level. It's OK between L and F. But if it's near or below L, add enough oil to bring the level to F."

Thanks in advance,
rx8cited

 

My assumption would be the fact that oil, like most liquids will expand when heated and contract when cooled. I don't know by how much the volume will change nor do I know how sensitive the (oil) stick is (how much oil is "missing" when it goes down 2 or 3 mm). But I would imagine that rather than take into account oil volumes at -20°F on a cool Albertan-winter afternoon vs. 117°F on a warm Dallas-summer afternoon and "standardize" the oil stick across such a temperature range, they elected to predicate everything upon oil volume at driving temperature. That makes sense to me.

 

Hi FirstSpin,
Thanks for your reply. The oil expansion thought had crossed my mind too - but I was not sure if that was it or if there was more to it.

You are correct about the oil expansion reasoning :D.

In this article
http://cartalk.cars.com/Columns/Arch.../March/09.html
the car guys Tom and Ray talk about it.

If that link does not work, try this one:
http://cartalk.cars.com/content/colu.../March/09.html

Thanks again,
rx8cited

 

How often do you have to check ?

 

hi rx-7~rx-8,

The Owner's Manual page 8-6 says to check it when refueling. I don't check it that often - I've been checking every 2nd or 3rd fill-up.

rx8cited