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My regular daily commute is around 80 miles each way but I charge at work so it's always roughly 50/50 electric / petrol. As well as trying to get the maximum out of the battery I also try get the best MPG when on fuel. On average I use about 0.65 - 0.75 gallons for the petrol part so around 52mpg. On a few longer trips 150+ miles I've been getting closer to 58mpg. I'm assuming the initial cold start of the engine has a noticeable impact on the mpg but the longer it has been running the better. I'm not convinced the theory of using hold at the start of a journey when it's cold is beneficial to the overall economy. The ICE is at it's least efficient from cold especially when it's put under extra load with lights, heating etc.

I try to be careful if I use hold as I worry about engaging hold at 70mph with a cold engine that all of a sudden it's being asked to work very hard with cold thick oil so I tend to try and let it warm up a bit by reducing speed. I've also seen various opinions about using hold increasing battery range but from what I have seen the way the split mileage is calculated is very clever and I notice when switching from ICE back to battery it will sometimes continue to total up the ICE miles for up to 3 miles after the engine has stopped and only start adding to the battery miles once that battery is back to the state of charge before hold was selected.

Typically with ICE engines mpg improves from new as the engine runs in. I wondered what sort of MPG people are getting once a few more miles have been covered?
 

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As long as you have decent oil in there then running it fairly hard on cold isn't too bad. When it changes over (or you switch to Hold/Mountain), watch the main screen to see what's happening - for the first minute or two, it continues to run on battery power while the petrol engine runs at a low speed to bring the oil temperature up a bit. Only when this has happened does the petrol engine start taking over power duties. This is specifically to cover what you mention.

I think for some of us, the petrol engine is used so little it's probably not even run in yet ;-) I've done 6k miles in total and probably only about 500 of them on petrol.

Generally people seem to get the same figures as you - it starts at mid to high thirties when it's cold, rising to mid 50s when it's up to temperature. That's at about 65mph.

This is (by the way) one reason why we have a petrol range-extender not a diesel one - diesels are much bigger lumps of metal and take considerably longer to heat up and are very inefficient until they are fully up to temperature. My old X-type didn't get warm going into work after 12 miles!
 

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Everything @Richard Gledhill says pretty much mirrors my experience over 13,000 miles.
The engine goes through a warm up cycle to ensure it doesn't prematurely wear.
My aim is to get the petrol mpg above 60 on a long run, but winter is a bad time to achieve that, as wind and rain seem to drag it down.
I got it down to 45mpg in the cold last week when it was running the engine due to the cold, even though it had battery capacity left :(
 

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Ampera aka IGOR
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Ditto and ditto.
I did wonder about this engine starting and stopping during a trip but decided that it is designed in that way and providing there is power in the battery, which there always seems to be due to the way the Ampera manages it, then when you select 'Hold' it does not suddenly disconnect the electric power and bring the ICE running hard to take over, it is a gradual process to transfer from the electric motor to the ICE. Even when the battery is 'empty' you will find that there is a changeover over quite a distance (seem to recall watching the display and seeing the battery mileage still climbing even although according the other display I was now running on petrol. I no longer think about the engine running hard on 'choke' and loads of petrol washing away the oil in the cylinder bores until it has warmed up.
 
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