SAE 10w30 full synthetic and change it once a year.
what grade of oil on this engine
straight 30 or a 10w30
your rings are most likely bad
5w-30..or any 30 w oil will work..takes about a half a quart no more!
My 6.75hp Briggs calls for 30wt, so I would make a reasonable assumption that the 6.5hp calls for the same.
SAE 30 weight.
Briggs and Stratton is a select brand of lawn mower. When oiling one's Briggs and Stratton lawn mower engine, it is best to use a high quality oil. One can find such an oil at their local home improvement store, such as Home Depot.
Briggs and Stratton only recommend using their own brand of lawnmower oil. This oil is available in stores for around $6 for 18oz. This particular oil is designed to be compatible with air cooled engines.
Briggs and Stratton recommends SEA30 oil.
A Briggs and Stratton 17.5 horsepower engine can use any type of small engine motor oil. A heavy duty motor oil is recommended.
In moderate temperatures, as in a lawnmower used in summer, most will use straight 30W oil.
SAE 30