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-   -   New fuel pump, better gas mileage (http://www.bimmerfest.com/forums/showthread.php?t=730362)

nedmon 10-19-2013 05:30 PM

New fuel pump, better gas mileage
 
All
I just installed a new Airtex pump in my 1998 528i along with a filter. The original, at 165K miles is now a spare. The Airtex pump is a nice assembly and came with all the hose clamps and wiring. I also treated it to a new fuel filter.

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?

Ned

mucho 10-19-2013 06:25 PM

New fuel pump, better gas mileage
 
Just changed mine also last month 99 528I w/181k, but treated it to original fuel pump part, I've read that after market parts don't go very far, but have noticed a slight drop in MPG. Need to give some time to really see any diffrence.


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AH673000 10-20-2013 05:12 AM

New fuel pump, better gas mileage
 
Better mpg? Could be your cars computer was trying to deal with lower fuel pressure to the rack. Could have been the pump or the filter. I use Airtex parts in all my vehicles( they make many OEM parts for USA built vehicles) and have always had great service from them .




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Fudman 10-20-2013 06:01 AM

Quote:

Originally Posted by nedmon (Post 7907305)
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.

nedmon 10-20-2013 09:39 AM

All,
Right now the computer shows 31.5 mpg and 65 miles travelled. I agree that it may be a measurement error but will post the MPG when I fill it next.

mucho 10-20-2013 10:22 AM

New fuel pump, better gas mileage
 
I average between 28-29 mpg, these numbers come from gallons used verses miles traveled. Computers are only a great tool, just do the real math.


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nedmon 11-13-2013 02:13 PM

All,
361 miles travelled, 12.5 gallons used and this is 28.9 mpg. Before changing the fuel pump, mileage was around 26/27 mpg
Ned


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