[Gasoline Fumes]

Anything between the two marks should be safe and approved by the manufacturer. Don't go lower and do check it very often. Owner's manuals usually say to add oil when it gets to (or below) the lower mark. I'd keep it at the max in a racing car. My Insight calls for 0w-20. I use 0w-16 and run it near the low mark, which is only two quarts in the engine. My oil gets changed once a year and my oil analysis from Blackstone Labs says I'm doing fine. $10 annual oil change and $30 analysis!