Disclosed are techniques for vehicle feature assumption evaluation. In an aspect, an assumption associated a vehicle feature defines (i) at least one response by an attentive driver to at least one in-vehicle human-machine communications interface stimulus, (ii) timing information associated with at least one in-vehicle driver action, or (iii) a combination thereof. Behavior of attentive driver(s) is monitored, and used to calculate a confidence level associated with the assumption being valid based on the monitoring.

A method comprises on board a hybrid vehicle and executed by a vehicle controller on board the hybrid vehicle, determining a pH based on a pH sensor positioned in a fuel system; and in response to a first condition comprising the pH being less than a first threshold pH, disabling an electric motor and propelling the hybrid vehicle with an engine. In this way, a risk of engine degradation due to fuel degradation can be reduced.

A hybrid vehicle includes: an engine configured to output power for traveling; a motor configured to output power for traveling; a switch configured to set a fuel economy priority mode, in which priority is given to fuel economy, and to cancel the fuel economy priority mode; and a controller configured (a) to operate the engine and the motor based on the switch setting; (b) to determine the presence/absence of degradation of fuel supplied to the engine; and (c) to prohibit setting of the fuel economy priority mode by the switch subsequently when determination is made that the fuel has degraded when the hybrid vehicle travels using power of the motor in a state in which the drive of the engine is stopped.

A method comprises on board a hybrid vehicle and executed by a vehicle controller on board the hybrid vehicle, determining a pH based on a pH sensor positioned in a fuel system; and in response to a first condition comprising the pH being less than a first threshold pH, disabling an electric motor and propelling the hybrid vehicle with an engine. In this way, a risk of engine degradation due to fuel degradation can be reduced.

An ECU determines whether or not fuel in a fuel tank deteriorates. A heating system is configured to be able to perform heating (engine heating) using heat of an engine which heating uses the engine under operation as a heat source, and heating (heat-pump heating) using a heat pump cycle without using the engine as a heat source. When it is determined that the fuel in the fuel tank deteriorates, the ECU controls the heating system and the engine so as to give priority to the engine heating over the heat-pump heating.

A communication device acquires schedule information in which a schedule of a user who uses a hybrid electric vehicle is recorded. The schedule information includes a traveling schedule for causing the hybrid electric vehicle to travel in a predetermined period. The predetermined period is a period from when fuel of an engine is refueled to a predetermined deterioration time. When a traveling distance in a long-distance traveling schedule is a first distance, an ECU increases a usage ratio of the engine in the predetermined period than when the traveling distance is a second distance that is longer than the first distance. The long-distance traveling schedule is a schedule included in the traveling schedule and in which the hybrid electric vehicle travels for a predetermined distance or longer.