H20 - Water
HC - Hydrocarbons
H/D - Heavy Duty
HEGO - Heated Exhaust Gas Oxygen Sensor
HEI - High Energy Ignition
HG - Mercury
HGT. - Height
HLDT - Headlight
HO - High Output
HO2S - Heated Oxygen Sensor
HP - Horsepower
HP - High Performance
HSC - High Swirl Combustion
HSO - High Specific Output
HT - High Tension
HTR – Heater
Hz - Hertz(Cycles Per Second)