Engine starts itself at 35 mph in deceleration

I've never noticed this. lease include temps, driving time, engine coolant temps etc. when trying to diagnose something like this.

 

On a short trip in freezing temps your engine coolant temp may not have been high enough to keep the ICE off. This is especially true if you had the heater or defroster on! If your SOC was low from gliding then that could have also trigger the ICE to fire.

This is one of the reasons that hypermilers use grille blocking in temps below 40F. When coasting with the ICE off the engine cools down pretty quickly at higher speeds.

 

But what was the ICE coolant temp? What was the SOC?

 

You see it with a scangauge. Same with the SOC %. Alternatively you can use the Torque App and a smart phone.

Without any of this data there is not much than can be said and even less reason to worry about it further. Get the monitoring devices.

 

It doesn't sound normal to me, particularly if you had the heat off.

 

Just buy a Bluetooth OBDII dongle.

Soliport ELM 327 Bluetooth OBDII OBD2 Diagnostic Scanner : Amazon.com : Automotive

 

Well 43 mph is a different story. If your speed is increasing past 43 the MG1 is forced to get the engine turning to protect the MG2 from overspeed. The engine must be turning once you're above this speed.
If you're coasting down in speed you're probably feeling a slight jolt as the system allows the engine to stop turning.
This is very normal and to be expected.

 

43 is normal 42 is the official. over that speed the ICE must be on that is by design so whichever electric motor is no over rotate ..

 

Its normal..., and no the ICE will not turn off until you drop below 43mph (when it is fully warmed up)...

 

When doing this, it injects a few drops of fuel for very brief time.

 

You won't.

Unless you purchase an aftermarket device to reveal what's actually happening, it's going to be a lot of hit or miss guessing. Sometimes, the engine actually does start up. Sometimes, the engine simply spins without consuming any gas.

Bluetooth devices (under $20) that work with a smart-phone app ($5 Torque) can be extremely informative.

 

How did you observer this ??? I have a SG so I can tell you and others as well that over 42-43mph the engine is turning weather or not consume gasoline that is something different but it will have 996rpm even when 'no power is coming from it' what you may feel is that the ICE puts out power to the wheels ...