thermal efficiency

Thermal efficiency measures how well a machine converts heat into useful work—basically, how much of the fuel's energy actually gets used instead of going up in smoke. It's expressed as a percentage, with higher numbers being better. For car engines, thermal efficiency usually hovers around 20-30% for older petrol engines, while modern diesels and hybrids can push into the 40-50% range. Electric vehicles, cheekily, don't have thermal efficiency because they don't burn fuel, but if you consider the whole power chain, efficiency can vary. Remember, thermal efficiency is the cold-hearted truth behind the shiny engine specs—always check the official documentation for exact numbers.