For nearly 20 years I have been using a very good quality fuel additive in my personal vehicles, as well as in our farm machinery. Most tests that I have done show around 10% fuel savings, while the product cost is only about 2 or 3%, so I’m ahead financially by 7%, give or take.
Here is a link to the company that I started out with in 1998.
There is a product for gasoline, as well as for diesel.
Along with that is a very high quality and functional lubrication system, including oil additives and grease.
The grease can reduce your total lubrication usage dramatically, and extend the life of the bearings etc. in your equipment. We personally dropped our volume about 75% when we switched over back in 1998.