Save fuel
By skipping gears on gear changes ie. 3rd straight to 5th instead of 3rd then 4th then 5th. Works on the way down as well: when leaving a motorway stay in high gear for as long as possible then drop straight to 3rd or even 2nd.
(Smale is stuffed, Thu 24 Mar 2011, 10:03, 3 replies, latest was 14 years ago)

Might cost you more in gearboxes and brake pads though.
Use an appropriate gear to the situation wherever possible -- because it is safer.
Having said that, the best way to get good fuel economy is to keep the car at optimum revs for than engine while accelerating -- if your car puts fuel into the engine while it's decelerating then it's old enough that using it is better for the environment than buying a new one anyhow.
Still, changing from3rd to gth, or other two-gear intervals, should use more fuel than changing properly -- since keeping constant revs is the way to fuel economy.
(you can read more in my book "A fooels gide to economy").
(Me, I'm not... in any way intoxicated, Thu 24 Mar 2011, 18:18, Reply)

I learned to drive recently
and was told by my instructor that there is nothing wrong with switching gears to the appropriate speed regardless of which gear you are in. Theres nothing wrong with changing from 5th to 2nd etc. if you have slowed down enough whilst braking.
( Peej, Tue 29 Mar 2011, 13:20, Reply)

There's a distinction to be made — the most efficient way to accelerate is to use every gear and use a very light touch on the accelerator, changing up each time before the revs get very high at all.

On the other hand, if you have already accelerated in, say, 2nd gear to a speed where you can easily use 4th or 5th, then there's no reason to oblige yourself to engage every other gear in between — there's nothing wrong with just bunging it into the gear you want.

For maximum efficiency, plan far enough ahead that you don't need to touch the brakes. If you're braking *now*, then you could probably have lifted your foot off the accelerator 30 seconds ago instead, thus making those 30 seconds more economical. That's not always possible of course — things change on the road, hazards appear, other people brake, etc. etc. — but if you can see that the traffic light 500 yards away will be red when you reach it, start coasting now; off-sliproads are made for coasting, and if there's no one behind you, you might as well start on the dual carriageway itself 200 yards before the sliproad; [add your own examples here]
(Sir Reginald Slapknackers last slapped his knackers at, Tue 5 Apr 2011, 21:03, Reply)