VW Passat - New Fuel Pump Gives Improved Fuel Economy Gas Mileage

I've recently needed to replace the in tank Fuel Pump on my VW Passat TDI as it had failed and the car wouldn't start. What surprised me the most was that the car runs much more smoothly especially under hard acceleration and also gives improved fuel economy (gas mileage) which I really wasn't expecting to happen. 

VW Passat TDI Replacement fuel pump failure

I guess over time the pump wears and becomes less efficient but it's not immediately obvious as the change is so gradual. It's only when you switch to a brand new pump that the significance of the replacement is clear.

There was a spate of Passat TDI diesel fuel pump failures early on in the model's life but the pump on my car had lasted 12 years and 185,000 miles. It's actually the first fuel pump I've ever needed to replace so even that mileage is quite low for replacement.