I have been reading about what you should expect for fuel mileage. I have noticed a steady drop in MPGs over the years. Like 15 years ago I took my 29.5 foot Coachmen on a long trip and got 9 mpg. Now...
Anytime additional products are added to blend a specific formula of fuel there is the possibility of a reduction of the available BTU or energy for a given volume of the fuel. Less energy per volume results in more consumption to achieve the same work.
Don't see many ditch diggers eating sprouts and tofu for lunch.