Before coming to this site, I reasoned that the best way to get real FE gains, while avoiding the BS, was to go based upon sound engineering principals. And so the next question I asked myself, is what general areas are there, that engineering says we could (at least in theory) help FE with. Here is the list I came up with:
1) Efficiently turning the fuel into "work". In theory, if you could burn the fuel more completely, or fail to "waste" energy (say out the tail pipe), you could get better FE.
However, I also realized that most changes in this area were beyond what I was likely to be able to effectively tinker with. You can effectively tinker a little bit (for example, by indexing your spark plugs, or carefully using a small amount of gas additives), but it's just a little around the edges. IMHO this isn't an areas that a small user can easily get big gains from (but every little bit helps).
2) Avoiding "losses" in the systems involved. For example, if you have a belt that is "slipping", you are wasting energy. As I see it, the main things that a normal user can do about this, is to just keep things running in good repair.
3) "Double-dipping" from the energy used. i.e. getting two (or more) "useful" things done from the SAME energy input. One of the more "extreme" examples of this is co-generation power plants, where the fuel not only produces power but also gives off "waste heat" that is used by a nearby factory or greenhouse (thereby getting two uses out of the same fuel). This one is a real "coup" when you can do it, as the 2nd/3rd/etc uses of the power are essentially "free" (as you have already paid the power price for the first use). However, the places were you can effectively do this in an automobile are limited. You might (for example) be able to use the "waste heat" (or "waste" exhaust gasses) of an engine to do useful work, after the engine is done doing its useful work (from the exact same fuel), but that's probably about as far as you can take "double-dipping" in a car...
Which brings us to 4) "Drag".
Given that objects in motion tend to stay in motion unless acted upon by an external force, science tells us that it should take virtually no gas/energy to maintain a constant speed if there wasn't "external forces" acting on the car. And most of those "external forces" go by the general term of "drag". So it follows that as you lower "drag", you should get closer and closer to the ideal of just setting a speed and continuing to coast without using up any additional fuel. As you will never fully get rid of drag (there will always be some "wind resistance" for example), it's impossible to fully get to the ideal. But I reasoned that there was a lot of potential in lowering drag, and that this was the one area that a normal person could usefully tinker with! And this theory seems to be supported by this forum, as many of the techniques this forum found to work, are really just different ways of lowering the various types of "drag" we encounter (be that drag from friction, rolling resistance, aerodynamic drag, or...).
But if you look at it from a "lowering drag" standpoint, IMHO it helps to let you see "the big picture". Because at that point, you are looking for ANYTHING that accomplishes the general principal of "lowering drag", and not limiting your mind to just the areas that someone has already thought of. This allows you more freedom to "think creatively", and still be working in a useful direction.
For example, it was that general principal/reasoning that first got me thinking about car lighting as a source of improvement. I already knew from general electromechanical principals, that the more electricity you actually use from a generator, the more "fuel" (mechanical resistance to turning the generator) you will need. So it stood to reason that lowering car electrical use would lower "drag" (from the alternator) and therefore (slightly) help FE (and tests on this forum, have since confirmed that theory). Which is why car LEDs (i.e. "energy efficient lighting") actually helps FE, even though that seems to be a major secret to most everyone else (ironically, even the companies that sell LEDs for cars, don't mention their FE benefit).
Likewise, it was the principal of "lowering drag" (in this case friction resistance) that caused me to want to do an extra good job of lubing up my wheel bearings. Because the more free the wheels spin, the less you slow down when just coasting. Again, the idea is to lower "drag", in this case friction inside the wheels slowing you down. And this really makes sense to anyone who has ever worked on a bicycle, as the more the bicycle wheels turn freely, the more you can coast, and the less work it is to move when you do have to pedal. Likewise, lowering drag in auto wheels, should greatly help FE even when not coasting (and indeed it does seem to help).
And it was even the principal of lowering "drag" that caused me to switch to high quality synthetic motor oil and transmission fluids. Because the more lubricated that the engine (and transmission) are, the less effort is being wasted going into friction. And that in turn means that more of your effort is being put towards useful work (i.e. greater FE). And I'm far from the first person to notice that better quality oil (or transmission fluid) can help FE a small amount all by itself!
And those are just examples of things that previously occurred to me. There are many other examples from this forum, that also prove the point (but for which I initially didn't think about). For example, all of the talk about "aerodynamic mods", is pretty much talk about lowering aerodynamic drag. And when you do such things right, they can be amazingly effective (just look at how effective "grill blocks" can be, for example).
Which brings me back to the general principal of lowering drag. Lowering drag just seems to be the "glue" that ties so many of these FE techniques/tricks together. And I will go further, and speculate that "lowering drag" should almost always be useful (for FE) unless it has some higher "cost" to it. For example, a solar cell can produce electricity, and thereby lower the alternator drag on the car. But when looking at FE, you have to weigh this against the extra weight of the PVC array, and any lowering of car aerodynamics that your mounting position might entail (as you don't want to trade one gain, for an even bigger loss).
So what do people think? Should we be putting on "our thinking hats", and trying to find "out of the box" ways to lower drag? Or is that really what we have been doing all along, and I'm just finally putting a name to it.
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