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Old 10-20-2013, 06:01 AM
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Fudman Fudman is offline
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Location: Sudbury, MA
Join Date: Apr 2007
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Mein Auto: '02 530i Sport auto
Originally Posted by nedmon View Post
The car now runs just as well as It did with the original pump but is getting a few miles better MPG.

I have no idea why this should be. Any thoughts?
In theory, there is no way a new fuel pump and/or filter should change your gas mileage unless some parameter within the fuel delivery system is changed. Since a fuel pump simply maintains fuel line pressure, changing the pump should have no impact fuel economy. More likely, your calculation of gas mileage is different from before and after. Are you using actual gallons consumed and miles driven (not the trip computer)? Are you driving the same route before and after under the same conditions? Are you comparing a large enough sample size? If not, your gas mileage calculations are just estimates. It will likely all even up over time.
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