Mods (@John Anthony
, etc), if you want to roll this into the merged thread, that's fine, but I thought this might deserve its own thread because I have some anecdotal insight and I thought people who are having issues might want to help prove/disprove what I'm seeing.
The merged thread.
After a wide range of driving conditions this past year, I believe this is (mostly) a software issue. I think what we can all agree on is there's some learning ability in the gas gauge/DTE software - where it's taking into account your recent mpgs (past two tank average is what I've "read") to calculate your DTE. I think there's also some factoring there for gauge "fullness", but am not entirely sure.
Anyway, what I've noticed over the past few months is that as I allow the tank to get closer and closer to empty before filling it (searching for the lowest gas prices mainly), the higher my DTE has gone, and the more I've been able to add to the tank when I get closer to empty. These past two tanks especially, I've gotten it down to ~5 miles to empty and found my DTE jumping 5-10% over what I would have expected, and getting very close to the 600 mile mark (after hovering around 500 for most of the year). I've also noticed it's taking slightly more than I'd expect to fill it, more than 15 gallons vs. 12-13 when I've only let it get down to 25 miles to empty. That doesn't make sense when I'm getting 35-40mpg; 25 DTE would translate to 2/3rd a gallon, not 2+ whole gallons.
I think this is because the software needs to see those near-empty readings to "learn" what an empty tank is supposed to read. If you're filling up at a quarter tank every time, it may never learn.
On the flip side, it may have to learn what a full tank looks like, too, so it's important to both fill completely and drive down close to E for it to register. I've seen the gauge not reading full, despite filling it, just once - this summer when I was towing a trailer across the Midwest, not knowing where the next station would be and filling up every 200 miles or so instead of when nearing E.
My advice (@reezick
, @kalagher @dtime1
,etc) - if you're having trouble getting the gauge to read full, or you're upset your tank won't take more than 13-14 gallons when "empty" - try this: for the next 3-4 tanks, fill completely and drive down as close to DTE=0 as you're comfortable doing - sub 10, if you can. Help teach the software what a full/empty tank looks like and you might start seeing improvements.
I know there's a couple on here who've gotten replacement tanks/pumps/sending unit/gauge, etc and have seen improvements. That doesn't necessarily negate the theory.