Tried EOC
 

I decided to try a bit of Engine Off Coasting, to try and recover some lost mpg after being an hour crawling in traffic after a road accident.
I turned the ignition off and coasted for a mile or so, then noticed my speedo was not registering (I have a GPS one I go by so seldom look at the car's speedo). When I checked the odometer I discovered this was not recording either. So no point in EOC as, though it will save petrol, it will not give me improved mpg figures.
I suppose I could turn ignition back on, but I don't really want the drain on the battery, so I guess it is back to DFCO and coasting with the engine ticking over.

You want to turn ignition back while EOCing for other things, like lights and EPS.

In the car I EOCed, I had one of the Scangauge displays set to battery voltage. I also regularly(one a week to at least once a month) charged the battery from an outlet.

My lights work with ignition off. Even the brake lights. I have found I can get by without the EPS, in fact I think it needs the engine running before it operates, due to the high current it draws, just as the rear screen does.
I have a ScanGauge, but unfortunately no facilities for charging the battery, unless I take it off the car.

There might something else besides the odometer you want on. I think the dash displays and lights can vary based on what position the key was in. There is also the brake boost accumilator on some cars.

It was the Sonic I EOCed. Even with the ignition on, while the odometers kept track of miles, the dash display ignored the miles coasted with engine off. So it was the only car I had that displayed a MPG lower than what I actually got.

Yea walking on dodgey ground with this in my opinion. As mentioned, lots of driver aids and safety features only work when the engine is running, and don't forget, if an accident occurred whilst performing this, you'd likely be charged with careless/dangerous driving and your insurance would be completely void.

I don't mind not being able to see the odometer. I switch it to Average mpg by default anyway. It is just that if it doesn't count the miles, as a mechanical one would do, then my calculations would be rubbish.
Brake servo doesn't get charged with engine off, but I am not braking when I am coasting, so that doesn't matter. There is always plenty brakes left for an emergency stop or even two.

I agree with this, though I do not know how they would know whether the engine was off before or after the accident, unless I was foolish enough to tell them. My dashcam doesn't record engine noise, and it would continue to record with the ignition in the Aux position.

There are two long sections on my usual run where I may try it with the engine off but ignition back on. They are only a couple of minutes in length, so I may give it a try. The road is quiet, no appreciable bends and no braking required.

You'd be surprised what you can read off an ECU. For example, a previous car I owned had the option to remap the ECU for an extra 25 HP within the first year/12k miles, but only if your engine hadn't hit the rev limiter for a combined number of (unknown) seconds to prove you weren't going to thrash the car.

Unless the accident involves death, or a life changing injury, you are lucky if the police bother to take photos/measurements. That is assuming they turn up at all.

Well mine did, near fatal and life changing injuries for the other driver and coincidentally it was in Scotland too, and it was a horrible 4 year process to sort the claim, and my car suffered compromised steering and braking mid accident, similar to what you could experience with EOC. But if you want to dice with death and save 14p, it's a free country my friend.