Another aspect of reduced maintenance that the Volt shares with other hybrids is drastically reduced brake wear and maintenance because most everyday braking needs are met by using the electric motor in reverse, recapturing energy to be stored in the battery and saving wear and tear on the brakes. My 2007 Prius with 140k miles has never required new brake pads, for instance.
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Brake wear is the most expensive part of normal automobile service. For my ICE vehicles from the past I paid about $1000 for front brake rotors, calipers, pads, brake fluid and labor. For all 4 wheels it would $2000. Currently it would cost even more.
Reduced wear of brakes is the most significant maintenance item for saving money on any vehicle - ICE, Hybrid or EV.
The cost of engine oil changes, transmission oil changes, coolant changes, air filters, fuel filters and drive belts are insignificant compared to brakes. EVs do not have any of these costs.
Jaak