Why does fuel consumption increase after an engine overhaul?
2 Answers
This is a normal phenomenon because after an overhaul, the clearances between engine components are too small, leading to excessive operating resistance and increased engine load. The specific impact depends on the situation. If only polishing was done, there might be slight effects on power and fuel consumption. Below are some common engine-related issues: Cylinder scoring: Cylinder scoring refers to deep grooves being formed on the inner walls of the cylinders, causing the piston and piston rings to lose their sealing ability when rubbing against the cylinder walls. This results in reduced cylinder compression pressure and loss of power. Fuel injection system failure: This could be caused by low fuel pump pressure, leaking or deformed fuel lines, or a malfunctioning fuel pressure regulator.
Over the years repairing cars, I've encountered many car owners complaining about a sharp increase in fuel consumption after major overhauls. The common root causes are assembly issues: for example, piston rings not installed properly or valve adjustments being inaccurate, leading to poor sealing, reduced compression pressure, and lower combustion efficiency, which naturally consumes more fuel. Another issue is improperly adjusted electronic systems, where the ECU's fuel injection parameters aren't updated, resulting in overly generous fuel delivery. New parts also need a break-in period of a few hundred kilometers after installation, so slightly higher fuel consumption in the first few days is normal, but if it doesn't decrease after a while, it's cause for concern. Poor repair techniques, such as uncleaned fuel lines or missing small components, can also affect performance in the long run. I recommend that car owners take their vehicles to a professional shop for a follow-up check, including compression ratio tests, fuel pressure measurements, and ECU fault code scans, to avoid turning it into a hidden problem. In daily driving, avoid sudden acceleration and maintain a steady speed to save on fuel costs.
