Chad D.

iTrader: (19)

+1
This is a very good idea.

PeteInLongBeach

Are you checking the oil exactly the same way each time (level ground, fully warm engine, 5 minutes after shutting off, etc.)?

Delmeister

Do you know what the actual relationship is: ie step# vs. rpm/load?

mbitterman

I was always taught to check oil on a level surface and a cold engine.

PeteInLongBeach

Mazda specifies checking the oil with fully warm motor, a few minutes after shutdown, and this is what the dipstick is graduated for. This facilitates regular checking when fueling the car. Oil expands / rises when hot, so if you top it off when cold you risk over-filling it.

Woody77

Digging around, I've seen .0004/deg F as the thermal expansion coefficient. For a 140f rise (40f to 180f), and a 7 qt system total (??) that's 40% of a qt of expansion.

Given that the oil temp is likely to be nearly the same (within 10f) every time on a 5min after shutdown, vs. the >100f swings in ambient during the year that some places have, it makes sense.

Of course, one way to deal with that 1/4-1/2 qt of change is just to keep the cold fill point at 1/2 qt low, since they so nicely provided that mark on the dip-stick. Although, one could also time your shutdown wait with how long it takes to fill a tank fully up.