I know this is easy but I've never mowed a lawn so here goes... what kind of oil do I need to put in a Troy Built lawnmower that 6.75 horsepower?

Thank you,

Straight HD-30 weight (thats a high detergent) of any good name brand (havoline, castrol, etc) Above 40 degrees Fahrenheit... I wouldn't even use it below 50 degrees though..

Use a 5w-30 or 10w-30 conventional below 40..
OR just use a 5w-30 or 10w-30 synthetic all year round. change the oil every 25 hours. This engine should take 20 ounces.

Should've read this thread first. Argh!