If you have a vehicle with a manual transmission and poor fuel economy, you might want to check your clutch operation. As a clutch gets old, it can start to slip in the higher gears. What this will equate to is a loss of motion and efficiency from the engine. In other words, less power is transferred to the transmission when you have a slipping clutch. So even if your engine is running perfectly, a slipping clutch can cost you MPG. Here’s a simple test to see if your clutch is working correctly.