In some embodiments, a fuel temperature sensor is located proximate to a vehicle component that is expected to experience fuel gelling, such as near or within a fuel filter, in order to obtain temperature information that accurately reflects the likelihood of fuel gelling occurring within the component. The proximate fuel temperature sensor can provide more accurate temperature information for components such as fuel filters that are installed at the periphery of the vehicle, compared to other temperature sensors that measure oil temperatures or other temperatures of centrally located vehicle components. In some embodiments, the vehicle is automatically started when the temperature indicated by the fuel temperature sensor falls below a startup temperature threshold value, and is automatically stopped after a predetermined time period or after the temperature reaches a shutdown temperature threshold value.

An example ferroelastic ceramic composition includes at least one compound having a relative chemical formula of A.sub.XB.sub.YC.sub.(1-X-Y)D. Element A, element B, and element C are independently selected from different members of the group consisting of yttrium, lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium. Element D is selected from the group consisting of phosphate, niobate, and tungstate. X and Y are each equal to or greater than zero and less than one. X and Y are collective less than one.

A cooling structure of an engine includes a cylinder head and a coolant temperature sensor. The cylinder head gas a first water jacket for cooling a combustion chamber and a second water jacket for cooling an exhaust manifold. The cylinder head includes a joining portion where coolants from the first water jacket and the second water jacket join together. The joining portion has a first coolant passage. A second coolant passage is disposed downstream of the joining portion. The temperature sensing portion is disposed in the second coolant passage. A coolant outlet of the second water jacket is defined in the first coolant passage, and is located at a position on the cylinder head cover attachment surface side in the first coolant passage. The temperature sensing portion is located at a position on the cylinder block attachment surface side in the second coolant passage.

An air/oil-cooled internal combustion engine capable of increasing accuracy in detection of the temperature of the air/oil-cooled internal combustion engine by a temperature sensor and carrying out the warm-up operation after the start-up of the air/oil-cooled internal combustion engine favorably. The air/oil-cooled internal combustion engine includes cooling fins that are provided on the circumferences of a cylinder block and a cylinder head; and a cooling passage that is provided in a combustion chamber upper wall covering a combustion chamber of the cylinder head and is used for cooling the combustion chamber upper wall with lubrication oil. The air/oil-cooled internal combustion engine has a temperature sensor configured to detect the temperature of the air/oil-cooled internal combustion engine by detecting the temperature of oil. The temperature sensor faces a cooling oil outlet portion of the cooling passage.

A combustion speed, for example, is estimated or evaluated, with a required accuracy, more simply than the conventional art, while reducing man-hours to produce a heat generation rate waveform of an internal combustion engine. An increase rate of a heat generation rate relative to a change in a crank angle in a heat generation rate increasing period (e.g., a first-half combustion period a) in which the heat generation rate increases after ignition of an air-fuel mixture is defined as a heat generation rate gradient b/a that is one of characteristic values of the heat generation rate waveform. The heat generation rate gradient is estimated based on a fuel density (e.g., fuel density .sub.fuel@dQpeak at heat generation rate maximum time) at a predetermined time set in advance in the heat generation rate increasing period so as to produce the heat generation rate waveform using the estimated heat generation rate gradient.

A combustion speed, for example, is estimated or evaluated, with a required accuracy, more simply than the conventional art, while reducing man-hours to produce a heat generation rate waveform of an internal combustion engine. An increase rate of a heat generation rate relative to a change in a crank angle in a heat generation rate increasing period (e.g., a first-half combustion period a) in which the heat generation rate increases after ignition of an air-fuel mixture is defined as a heat generation rate gradient b/a that is one of characteristic values of the heat generation rate waveform. The heat generation rate gradient is estimated based on a fuel density (e.g., fuel density .sub.fuel@dQpeak at heat generation rate maximum time) at a predetermined time set in advance in the heat generation rate increasing period so as to produce the heat generation rate waveform using the estimated heat generation rate gradient.

The present invention provides a novel combination of devices to measure and transmit to an electronic controller data pertaining to differential pressures, temperatures, regeneration status, exhaust content, accumulated gas consumption and substitute fuel consumption. The electronic controller compares the data to thresholds; when the controller receives signals indicating these thresholds or limits are met, the controller causes the gas substitution rate to be diminished or set to zero until after-treatments elements are fully regenerated thereby facilitating integration of a mixed fuel system with an application internal combustion engine.

An air/oil-cooled internal combustion engine capable of increasing accuracy in detection of the temperature of the air/oil-cooled internal combustion engine by a temperature sensor and carrying out the warm-up operation after the start-up of the air/oil-cooled internal combustion engine favorably. The air/oil-cooled internal combustion engine includes cooling fins that are provided on the circumferences of a cylinder block and a cylinder head; and a cooling passage that is provided in a combustion chamber upper wall covering a combustion chamber of the cylinder head and is used for cooling the combustion chamber upper wall with lubrication oil. The air/oil-cooled internal combustion engine has a temperature sensor configured to detect the temperature of the air/oil-cooled internal combustion engine by detecting the temperature of oil. The temperature sensor faces a cooling oil outlet portion of the cooling passage.