My 6.75hp Briggs calls for 30wt, so I would make a reasonable assumption that the 6.5hp calls for the same.
what grade of oil on this engine
SAE 10w30 full synthetic and change it once a year.
A Briggs and Stratton 17.5 horsepower engine can use any type of small engine motor oil. A heavy duty motor oil is recommended.
A Briggs & Stratton engine usually costs anywhere from about $170 to $1600. The cost of the engine will depend on its size and its features. A mid-range cost for this type of engine is about $400.
sae-30
SAE30
that is not a good model number for briggs. also you need the type.
On Briggs and stratton or techumseh.com Just go to ask.com and type in the brand of product and it should come up.
48 oz
5w-30..or any 30 w oil will work..takes about a half a quart no more!
Briggs and Stratton does contract anyone to build mowers. The mower manufacturers contract Briggs and Stratton to build their engines (or whatever engine is on the unit). That is why you can have a Briggs and Stratton on most any type of mower. Same is true for Kohler, Tecumseh, etc. Not to say that the engine manufacturers do not build their own type of outdoor power tool but as the question states "snapper mower". Also keep in mind that if you have a snapper mower with a Briggs and Stratton engine and you need warranty work on the engine you need to go to an Authorized Briggs repair facility where as if you have a mower warranty then you need to go to an authorized repair facility for the mower manufacturer.
take the old plug to a mower parts store & tell them you need a matching one for a push mower