Economical Motoring
Some of us went through this in the oil crisies of the 70's and 80's. Cars got smaller, and more economical. Speed limits as low as 55mph were introduced (in the States). But in the 90's and 00's it was back to fast, big, powerful cars. That's all changed, but this time it's hit really hard, secondhand car prices on big cars have plummeted, and there's no going back (probably).
There are plenty of sources of information regarding economical motoring tips. Here's a distillation of the simplest and most practical ones.
1) Drive smoothly - this will give you the biggest immediate gains, typically 30% improvement (for example of test showing this, visit http://money.cnn.com/2006/05/01/Autos/driving_for_mpg/index.htm). Each time you apply the brakes (except after coasting downhill) you are shedding speed that you built up by burning fuel. Smooth driving mimimizes braking and shows that you have used less fuel to reach your destination.
2) Drive at lower motorway speeds
A t higher speeds air resistance becomes a significant factor. In fact air
resistance quadruples for every doubling of speed. Air resistance at 70mph
is about double that at 50mph. Combining this with tip 1 could nearly double
your economy if you do a lot of motorway miles.
3) Keep your tyres fully inflated
Under-inflated tyres create more resistance when your car is moving. Some
tests suggest you'll save 5% on fuel. Also the tyres will last much much
longer so you'll save there.
4) Move off the moment your engine starts
Modern cars do not need to be warmed up; they will warm up quickest when
driven and your car is twice as thirsty until it is warmed up. Also, warming
up at idle is pure fuel wastage and causes a lot of engine wear.
5) Idling at standstill is wasting fuel
If you're likely to be at standstill, switch off the engine. Easier said
than done but at railway crossings etc. it's predictable.
6) Minimize airconditioning
Aircon puts a heavy load on your engine (relatively very high at standstill
or at low speeds). Many cars make you adjust internal temperature by mixing
chilled air from the aircon with warm air. If that's how yours works try
using the aircon intermmitently. Note that at high speeds aircon might be
more economical than having windows open due to drag.
7) Change up gears quickly
Modern cars are designed to pull strongly and efficiently from low revs.
Change up at 2000rpm for diesels and 2500rpm for petrol. (Don't allow the
engine to labour though.)
8) Don't accelerate uphill
On long gentle inclines such as you find on motorways, try keeping the accelerator
in the same position as it was before the incline and allow the speed to
fall off a little.
9) On motrways used cruise control
Cruise control can save fuel because you can step up and step down the speed
in small controlled increments, and because you won't accidentally increase
your speed over what you have planned. On uphill sections disengage the
cruise control, or reduce the set speed since the cruise control will try
to maintain car speed by depressing the accelerator.
More about this at: http://www.hypermiling.com/cruise-control-saves-gas.html
10) Shed excess weight and drag
Just as in Formula 1 racing, more weight means your car will use more fuel
to get up to speed, and you'll have to brake harder to lose speed. If you
have unwnated (heavy!) items in your boot, take them out. Don't drive around
with a roof rack or topbox if you're not using them.
11) Have your car serviced regularly
This is more important on older cars. Newer cars have onboard computers
that tune the engine, older cars don't and will need regular tuning to run
efficiently.
12) DRIVE SAFELY
Don't compromise driving safety to save fuel. In particular, DON'T FREEWHEEL
(CRUISE DOWNHILL) IN NEUTRAL, you will have much less control of your vehicle.Newer
vehicles with fuel injection will stop pumping fuel when you take your foot
off the accelerator pedal so you don't need to coast. If using cruise control
remember to brake when necessary!
The Cruise Control Debate
It's not entirely obvious whether it's a good idea to use cruise control to save fuel or not. Overall, it'll probably help you save, but here are the pros and cons.
Pros
You stick to the speed you plan to
You can increase / decrease speed by small amounts
You start thinking further ahead so as to use the cruise control rather
than the brakes
Cons
Throttle is being adjusted continuously
Speed maintained on hills - throttle opened ; try lowering the cruise control
setting or disengaging on uphill stretches
Hard to control in heavy traffic
Useful references
http://www.savefuelsavemoney.co.uk/carfuelsave1.htm
http://www.vcacarfueldata.org.uk/information/hints-for-less-environmental-damage.asp