If oil expands or contracts when hot, and how much at what temperature could be debated for days. From the practical standpoint, I doubt if there is a cup full of difference either way. I don't have a problem checking my oil with a cold engine as long as it hasn't been started. If you start the engine and shut it off cold, it will take thousands of Seybolt seconds for the oil to drain back to the pan. Hot or cold what is important is to pull the stick and wipe it before dipping it again to take a reading. These modern oils will stay at the last highest reading for weeks. You can't just pull the stick and take a reading. A tip for you guys maintaining several cars and wasting time getting the oil level correct after an oil change. To save time when I had a service facility going full tilt years ago, I had my mechanics sprnd extra time and carefully determine the correct amount of oil they put in a car. Then with a set of number punches, they punched ,for example, 6.5 on the dipstick. When the car came back for future service, the mechanic just had to check the #s on the dipstick. Also you troups and troupettes with diesel engines with the filter up above will leave a quart of dirty oil in the car if you don't remove the filter cover before draining the oil.
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