Hi Bob and welcome to Just Answer!
I will help as I can, what is the question you have?
In my opinion you can either run the factory Autolite spark plugs that come in it or run a platnum to get more distance between changing plugs. The spark plug gap should be .052 to .056 of an inch.
Some other things you want to check is the air filter and make sure it is not clogged or dirty. You could switch to a K&N cleanable filter which aloows more air flow into the engine over a stock paper filter, this would help gas mileage a little. Afuel injection cleaning will also help the fuel mileage some.
All in all it is a total of the small things that will get you some better gas mileage, but remember your driving habits and his driving habits can be different and can account for a large difference in gas mileage.
Lastly don't get pulled into these gimmick things that promise better gas mileage like the intake tornado, the magnets on the fuel lines. They don't work, if they did the manufactures would be using them.
Please let me know if you need further help