I would like to share something here that i experienced a few years ago. I do not understand the why of it, but it has worked several times with the same levels of reduction in fuel consumption for the distance travelled. Perhaps nothing can come of it, but i figure that if it is shared, that there might be some remote chance of it giving ideas or "aha's" for other things people might be working on. Anyway, here it goes;

Before i explain, some notes are in order;  For a long time, i have been recording my fuel consumption against the distance traveled. That has been done by filling the tank up to full, recording the travel meter, and then zeroing the travel meter so as i know how far i have travelled at the next fill up. I am well aware of city driving having different results to highway steady drive cruising, and have tried to make comparisons with same types of driving, and also as long a distance between refills as possible. I figured that if i travelled a short distance before refills, that if there was a slight inaccuracy of the fuel shops pump's stopping or "fill level" detection point, that the data would be more distorted, than if using a lot of fuel.


I had a 5 litre (Roughly = 1.25 gallon) plastic fuel container filled with petrol (that's gasoline for USA people) in the rear enclosed storage section of my sedan type car, that we in Australia refer to as the boot. At least this part of Down Under.  The fuel had been in there for 6 to 12 months. I recalled some 2nd hand information or claim that fuel goes stale, so i figured that i better put it into the tank during the fill up, and then freshly fill up the emergency container to keep in the boot.
  At this point, i was about 4 hours from my home city, and about to return home. I recorded the amount of fuel consumed by using the amount of fuel put into the vehicle that moment, recorded the distance travelled to that point, and reset the trip meter to zero (as i had done during fill up before i left my home city several days earlier)   So, out of the full 60 litre fuel tank, 5 of those were the stale fuel, which had been subjected on and off to heat, and compression it seems. A ratio of 1 to 12. 
When i reached my home city some 4 hours later to fill up, i went over the calculations several times , and double checked the amount of fuel on the fuel invoice from the fuel station. It was out of the norm, and i didn't understand why the car used much less fuel.

I have repeated this several times, with always a reduction of fuel for the distance traveled. The car was always more responsive with the stale fuel. I noticed two factors that it needed. A certain amount of time, and also heat. During summer my vehicles boot (as i said earlier, it is the rear storage space of a sedan), gets hot. It is a white car, but still can get hot on the hot days. I found the improvements were less obvious or did not happen at all in the colder weather. It seemed to need heat conditions. The container is a black plastic, and each time it expanded by a small amount, as it would look partially blown outward.

When i had it in the boot for about two months during hot (on and off hot) weather, i always got the same gains with the same type of city driving and more or less same routes. I went from 12 Litres per 100 km, to  9 Litres per 100km. I guess that might translate into a 33 percent improvement for the MPG people who have different measuring systems.   
This is getting a little bit off topic, but thought i would also mention my having toyed with Acetone in the fuel with improved results, to which i noticed most of the improvement occurred during the first 100km if i go by the position of the fuel meter (roughly 60 miles). 

I was wondering several things about this, and have mentioned it to a small number of people.
The automotive shop sales person was ok until i shared some contemplated ideas in order to try and understand it, but then he developed instant amnesia to any results i shared and started yielded mantras that i now recognize as inherited from Academia. Arguing for impossibility.  Meanwhile i have not even lifted a finger, yet apparently i was in violation. Its kind of funny in a way, but its no fun being the blackboard guy spewing out the mantras like an avid preacher. Little realizing he is doing the bidding for someone else and ignoring the bigger picture, and real world results.

Someone else presented me an idea that the plastic from the container might be mixing with the fuel, and converting or creating whatever is occurring.
My own ideas were based on looking at things from an energy and essential nature perspective. Looking at the qualities of things. There was an obvious expansion of the container, and thus a compression. Maybe that compression in the container was energetically creating a springy quality in the fuel. More explosive. Bringing that essential quality or nature to the application or conditions of its use in an engine. They are just some thoughts. In a way i don't care about the how so much, but more about the results. The how can come later or evolve over time, if one really wants to know.