[RedDevil]

Hi Laszlo, welcome at Ecomodder.

If your car is a true 2014 Insight you do not need to worry about oil consumption. The 2012 and early 2013s had a piston ring problem, earlier and later Insights don't.
The problem is mostly limited to the USA, it may be fuel dependent. But Belgian member 'Rode Schicht' at HondaHybridClub.nl • Index page seems to have it too. He experimented with thicker oil, to no avail.

Honda acknowledges the problem and issued TSB #16-101 to repair the issue.
You should contact Honda to find out whether your car is in the range or not.
Loads of info on InsightCentral.net .

I tried my hand at a plugin conversion for the Insight, even have my own thread.
The Insights hybrid battery pack does have 2 terminals well hidden in its internals, but it does sense abnormal current flow.

I made a buddy pack using 36 12Ah LiFePO4 cells, grouped in 3 isolated subpacks each with their own BMS and crashproof metal housing.:

The pack is able to produce 55 Amps at 116 Volt, but the Insight throws IMA fault codes if hooked up to it.
If you contact on while the pack is connected it will also immediately throw an error.

So I have relays on both terminals to separate the pack, and a switch to power them only after I started the car. Also invaluable is my UltraGauge OBDII device, which not only shows lots of vehicle data but also can reset the fault codes the IMA system throws...
It does not show specific IMA data, sadly. Retepsnikhep at InsightCentral.net has made a device that does just that for the first gen Insight and was planning a version for our cars, but housing projects got in the way.

I have used a lamp shunt to limit current, which works to some extent; the buddy pack draws to near empty in about 5 hours of driving. It does shorten or prevent the mild recharge that happens after speeding up to merge the motorway, and it may prolong the EV mode in slow zones a bit. The overall effect on fuel economy is marginal.

I am not using the buddy pack now, but am planning a revised version with volt and amp meters in the car, a diode bank to prevent back current on deceleration and ideally an adjustable current limiter.

If I lose heart on the project I may rebuild the cells into a 12V pack to replace the lead acid battery and prevent the car from charging it, to do that at home or with a big PV panel instead. That setup won't throw IMA codes and solve the Insights weakest point - that lead acid battery... If that goes the car throws all kinds of weird errors, as one by one the systems detect malfunctioning due to low voltage. Even the IMA control system is powered by the 12V battery! I therefore monitor the battery voltage on my UltraGauge almost as vigilantly as the economy readout.

You got a good car. Check out the VIN to see if your car is due for a piston ring replacement. Do not build a buddy pack