I have a 2015 Volt with 98k miles. Still drives great and charges to full capacity. Chevy dramatically over built the first gen, it was the second gen where they were forced to actually limit their design based on lame goals like "making a profit"
Lifetime 172 mpg over 60,000 miles!
It gets around 42 mpg when running purely on the gas engine. Based on the distance I have traveled and the amount that I have used the gas engine, it works out to 172 miles per actual gallon used.
MPGe is what you would refer to for your fully electric car.