That's what it is called on this side of the pond.
>I expect Diesels, like petrol engines, cut the fuel off completely
>on throttle overrun, just as petrol engines do, and inject fuel
>to keep the engine running when in Neutral.
True but irrelevant. When the engine is spinning at higher RPMs the engine resistance sucks a lot of kinetic energy. The amount of fuel needed to replace this kinetic energy is higher than the amount of fuel saved by not using idle.
With the right driving techniques, you can really save big. For example: did you know that you can go 60 miles on precisely 0 gallons of gas? You can - by coasting with the car in gear!
The overrun fuel cutoff feature interrupts fuel supply to the engine so that not a single drop of fuel is used. The best time to apply this clever little method is when you’re going downhill or approaching a red light, which is when you can also benefit from the engine’s braking effect.
You’ll also save fuel by disengaging the clutch. This is particularly effective when combined with predictive driving to coast on a long stretch of road. Coasting downhill is effective, too, but only if the gradient is not too steep.
Yea its called drink driving here as the threshold is much lower, you dont have to be "drunk" to be over the limit, far from it!
Anyway, I live in a very hilly region and although I only passed my driving test 9 years ago, ive probably done close to 100,000 miles so have had plenty of time to experiment. Although coasting in gear uses 0 fuel, the brake effect means you have to accelerte sooner, where as coasting in neutral, gravity takes you faster and further so the need to accelerate arises less often, if at all on some stretches!
I am not going to argue, because I am never going to convince anyone anyway. But I ask - if coasting with the engine disengaged saves fuel, why are free-wheels not found on cars? The old Saab with the three-cylinder two-stroke engine had one, back in the '50s. There is no technical problem fitting one, and with all car companies claiming to be working for better fuel economy (driven by Government, no doubt) a free-wheel would be an easy fix - if it worked.
... In ECO mode, the clutch was disengaged when the accelerator pedal was released for maximum economy, so the car freewheels as much as possible, with the clutch re-engaging as soon as the accelerator pedal or brake pedal is touched. ...
There are VAG group cars with DSG gearboxes over there, but my understanding is that auto-freewheel is disabled for cars in the USA. I think this was because people threatened to sue VAG saying that the engine-braking wasn't slowing them down quick enough...
In my 1998 Honda Civic EX coupe I used Mobil 1 synthetic motor oil during the 60,000+ miles I owned the car. Averaged over 34mpg despite the cold Chicago winters. I highly recommend synthetic motor oil for fuel efficiency, easier cold weather starting and great engine protection due to better flow on startup, cooler oil temperatures and less oil breakdown.