Anything you can do to increase air flow through the engine may improve mileage. Keep in mind, you are trying to overcome friction with a motorized vehicle. With that in mind, weight of vehicle is a primary concerns. Second is efficiency of the engine. Third is leverage, which is gearing and tire size.

The six points you mention deal with the engine and making it run more efficient. As to whether they work or not is open to debate.

Synthetic oils are popular but come with disadvantages. If you start a new engine with synthetic oil it will prolong the life of the engine. If you change regular oil to synthetic in a high mileage vehicle, you are asking for problems in the form of oil leaks.

With newer engines and increasing use of sensors monitored by a computer to control the engine, tweaking the computer does help performance and mileage. Not sure you will see much difference with an ÔÇÿ05 vintage engine.

I have seen many claims about magical properties of new technology and spark plugs. There appears to be a lot of hype with little substance.