[hey joe]

Where I was it was very cold over the Easter week-end. This seems to clobber the mpg on diesels even on a run after the engine has warmed up. Don't have any data to prove this ... but it seems to happen !!

[phil200tdi]

Originally Posted by djgandy

That's talking about accelerating down hills and not up hills though. He was motorway driving, which is mainly flat most of the time. That's the same on a bike or anything, you use gravity to build momentum. The thing is you drop 20-30 mph going back up the other side of the hill, you can't really follow safely using such a technique!

Check this out:

http://www.flixxy.com/audi-a8-diesel.htm

[Davidlindsey]

Originally Posted by phil200tdi

From Wikipedia:

Driving over "rolling" terrain, with gentle up and down portions, can usually be done more economically (using less fuel) by a skilled driver viewing the approaching terrain, by maintaining a relatively constant throttle position and allowing the vehicle to accelerate on the downgrades and decelerate on upgrades, while reducing power when cresting a rise and adding a bit before an upgrade is reached. Cruise control will tend to overthrottle on the upgrades and retard on the downgrades, wasting the energy storage capabilities available from the inertia of the vehicle.

good post and excactly what i do , accelerating down hill is almost free speed then just looking ahead you can adjust were as the cruise cannot do that.
i will cruise at 65 ish then gently creep up to anything up to 90 going downhill then let it just ease off on the flat again.