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Old 10-12-2012, 07:38 AM
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doru doru is offline
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Location: Calgary
Join Date: Sep 2007
Posts: 4,703
Mein Auto: 2003 530iA
Need some mpg improvement ideas

I posted this on Roadfly, but there isn't much traffic there, so here it is:

My car runs beautiful, however, the mpg is creeping up steady, and I ran out of ideas. The mpg is city driving related. i haven't been on a highway in a long time.

Up until about 4 years ago, the mpg was around 10.8 - 11.2 l/100Km (21.7 - 21 mpg). Then, it started to go up ever so slightly. Today I am at around 13.2 l/100km (17.8 mpg), and the trend is still going up. I will post a list with engine related stuff I did on my car, maybe this will help:
  • ATF was changed together with filter in fall/winter 2007/08 (55k / 88600Km)
  • Winterized CCV 2008 -feb
  • New pre-cat O2 sensors (Bosch) - Oct 2008 (66k / 106000 Km)
  • Beisan vanos seals Aug 2009 (74 k / 120000 Km)
  • New fuel filter Sep 2009 (75k / 120000 Km)
  • Cooling overhaul (incl belts, pullies, hoses, etc) & new DISA May 2011 (89k / 143000 Km)
  • New injectors (OEM) Sep 2011 (91k / 147000 Km)
  • Cleaned TB & ICV. New MAF (OEM), new sparkplugs (NGK), new VCG, replaced all vacuum hoses (Jul 2012) (99k / 159000 Km)
Other maintenance was also done, like oil changes, coolant flush, brake fluid flush, etc and various engine not related maintenance. But this mpg up-creep is just puzzling. My driving habits or route did not change, and I use the same Shell V-power gas since I purchased the car in '06 (with the odd different brand fuel once a year or so).
What did I overlook? I think I will change the post-cat O2 sensors as well regardless of "monitoring" status only. But I am not sure this will change the status-quo.

Last edited by doru; 10-12-2012 at 09:49 AM.
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