Modern automatic gearboxes will not shift up until you've achieved a predetermined minimum speed. This is noticeable towards the last few gears.
The upside of this is that it guarantees that your engine are at the revs when it generates sufficient torque to carry you on into the higher gear without much loss in acceleration and without consuming more fuel in the process.
The downside is that the gearboxes are unable to tell when you don't need that additional torque. Like going downhill or slow cruise on a flat road, this safety program makes your engine rev higher & consume more fuel until you achieve the minimum speed before it allows the next gear change.
It will always assume the worst in that you're climbing uphill and will not shift up until its certain you're fast enough.
You can override this program for gearboxes with the steptronic/tiptronic ability. Just notch the gearbox into manual and shift up a gear and then return it to "D". If the gearbox kicks down a gear during or back into the original gear after the process, you're doing it too early and not yet at enough speed to save any fuel from this trick.
Through trial an error, you can find a speed range where you can notch up the gear to reduce revs and save a bit of fuel without having to increase speed to get the auto gearbox to finally shift.
by BenjaminWKI on February 08 2011
this tip works for 32% of voting Fuelly members.