[Butterballz]

Originally Posted by theadmiral976

Do you calculate your mpg at the gas station? Or have you just observed the tank gauge dropping faster than you might expect? The reason I ask is that the fuel level sending units in this car are not the greatest in the world. Lots of people have issues with the sending units gumming up over time, particularly the secondary sender on the passenger side (for LHD cars) of the tank. There are a couple threads about this but to sum it up, essentially, the sender-B tends to slowly progress towards infinite resistance over time and can cause the gauge to float abnormally slowly or quickly, particularly at the extremes of travel. I had an issue for a long time where my gauge would never show full - others have had issues with the lower quarter of gauge travel would proceed really quickly.

Just based on your log above, I would be confident in saying your trims look pretty darn good. Back when I ran a stock car, I would routinely notice total trims anywhere from -9 to +7, even when the car was only a few thousand miles old. Without the vacuum and load data, it is impossible to be 100% confident, but my bet is you don't have anything that would cause more than a slight (normal wear and tear-related) change in fuel economy.

Another thing to think about is your O2 sensors. I doubt you have an issue with either the wideband or narrowband, but tracking their voltages could be really helpful as well just to be sure. The early narrowband sensors used in the manufacture of these cars were replaced with a new version, I think in 2015. If you have an older car, it's not impossible that the narrowband has gotten contaminated; although, it sounds like you haven't modified the primary cat so it's not too likely in your case. For me, within about 5,000 miles of switching to a catless header, I fouled the narrowband sensor which started messing with my trims (and thus fuel economy) in specific situations.

I reset the trip odo to zero when I fill then compare the miles to the fuel gauge. Noticed some differences from before. Usually, I could get over 200 miles before hitting the 1/4 filled mark. Now I usually get under that. I drive the same route 5 days a week so not much differences with the route. Fuel gauge seems consistent still when I checked the gallons filled during gas up.