The goal of this instructible is to cover all aspects that affect MPG, regardless of which car you are driving. Of course the type of car and shape along with other car specific tips will be added in.
If you are looking to buy a car, this can help you to identify features of the car that help with MPG.
Here are some links that I found useful: www.fueleconomy.gov
The list is in general in order of effectiveness on mpg.
1. Route (Engine Load and ON time)
2. Weather (Atmosphere and air intake)
3. Tires and Road (Energy Transfer)
4. Driving Style (Personal habits or states of driving)
Step 1: Route and Idling
Idling is using fuel when the car is not in gear or not moving. That is not efficient so having the engine on for as little as possible helps. When you park, turn it off, and only turn it on right when you are about to leave. As long as you are not going to be in the car for more than a couple hours, the battery can handle playing the radio or running the fan, windows, if you need that, and will not need the engine running, well unless you need heat or AC, or whatever.
The route and speed are major determinants of MPG. There is sometimes a difference between the fastest and shortest routes, but which route is the most efficient? It is known that delivery drivers try to minimize making left turns to speed up the routes, because no waiting at left turn lights. Efficiency is a little different, in that it is lost when you have to stop and go. Having a route with steady traffic, less stopping is better.
Most cars have a speed at which they are most efficient. It is usually in the lowest RPM and the highest gear. It can vary from car to car, but is usually around 40-50 MPH. This is slow enough to reduce resistance as well.
If you live in a dense city, you will not always get up to that speed, and if you do, it will only be for a short while.
Any time it is stop and go the best way is to "avoid using brakes" because they are actively taking energy out of your motion. Try to get to the overall traffic average speed quickly, but not the fastest you can like riding up on the car in front, if there is a stop you don't have to go so fast you will get there and stop anyway.
"Speeding up to the red" wasting gas causes stress. This driving style is influenced by routes with a few lanes wide and straight roads with frequent lights.
Step 2: Weather
Air resistance force increases as the speed goes up by the equation in the first link here:
And the shapes and comparisons of objects are here:
In the rain, it might create more drag because of the density of the medium, but not sure. Looking for more info on that.
When the temperature is cooler, you get better efficiency, because the air is denser and has more oxygen.
You could also use a cool air intake which are supposed to take air from closer to the ground, which is cooler.
Step 3: Never Finished
This will never finish as more ways are invented to increase efficiency and new types of engines are created.
Design of future cars is also a good way to increase efficiency or power.