Abstract: An engine provides a self-adjusting system and a method to save fuel in accordance with a practical driving state of a vehicle. The engine self-adjusting system includes an information center and a plurality of onboard computers. Each onboard computers has a vehicle controlling module for adjusting a response features of the engine so as to reduce influences of improper driving manners. An optimized standard road resistance characteristic coefficient is applied as a more valuable reference, so that the fuel consumption is efficiently reduced while keeping the vehicle powerful.