Gas tank level sensors are rarely in OBDII. The ECU does not need to know how much gas is in the tank, so the fuel level sensor is only connected to the gauge on the dash. Nobody is trying to hide anything from you. Rather Toyota did not make you pay for an extra wire in the wiring harness that would tell you something you already know.
Ultragauge will not really tell you anything important. The ECU will throw a code if anything bad happens. Also the ultragauge MPG calculator is terribly inaccurate.
My best guess at the cause of your problem is your trip distance. Driving 3 miles will barely get the car up to operating temperature, especially in the cold season. If all or most of your trips are this short, it can make a big impact on your MPGs.
However if your old car got better MPGs in the exact same usage, then something doesn't add up. My bet is that we are not getting the entire story. Either there is a problem with your measurement methods (either with this car or the last) or your trips are too short... possibly combined with other issues. No single issue should cut your MPG in half, no matter what, barring a stuck e-brake or towing a trailer.
Is your 3 mile commute all on city streets with lots of stop lights?
Well the temp is at the midrange on the car meter and the Ultragauge is saying 185F within the first 3 lights to the main road Castor Ave. I know its eating up gas faster because I use to spend $12-$15 tops now i'm spending $20+ and driving less in this 2010 XLE. According to EPA my 1995 Camry had lower 18 city and no Variable transmission which supposedly increased performance and MPG.
It's 3 miles to work 3 miles back and couple miles here and there about average of 10 miles a day and 8 miles on 2 days off in a week. As for my calculations if my trip computer is not working correctly and the photos of the gas station meters are displaying incorrect information I don't know how you could mess up calculations. Take trip mileage from last fuel up or subtract OM miles then divide it by the gas of the starting trip/OM. It shows the same results.
Even took photos of my dash before fill-ups and after to document the gas needle position and MPG readings off the dashboard. Nothing is altered to the car since I got it 2/20/2013 now I do hit a lot of lights on this because 3 miles takes me 15 mins in the morning to get to my destination and 20 mins going home during rush hour 6pm. But like I said I travedl on I-95 and got 15-17 mpg according the dash MPG AVG. Tank drops a notch down on 15-18 mile HWY trips using trip B readings.
I been told the dash is wrong and Ultragauge is inaccurate but at this rate beside taking 50 photos since march 6th its getting a bit desperate here for perspective tracking. All I get told is it's impossible yet I been driving to this same spot for 14 years and had a previous car 18 years and this one just few months and it's a culture shock I know but I just see the same bad results over and over so looking for some insight that's all.
BTW my link is using trip mileage. My alternative tracking is on fueleconomy.gov using odometer readings. Which give the same results. I just like to know how is fuelly.com giving me 18.9 -1.2 AVG MPG when my highest is 16.7, 16.6, 12.3, 13.9 mpg. A bit misleading there. Tried changing to partial fill up and full and nothing changes. Given I only been using this site for a month now but I've tried every which way to track my fuel ups and still the same results.
14.9 AVG MPG regardless of that 18.9 listed on my profile. Anyhow that's taking all my trip miles recorded driving up to the gas station and filling up from the last time. 313 miles and 20.99 gets me 14.9 average. So that's mixed in with I-95 driving 20 miles and 30 miles to the dealership being on route 130 South hitting 3 lights the whole way there and no 3-4 lights getting to I-95 hwy. So to sum it up 100 miles is visiting the dealership x1 for diagnostics check and 3 trips to other townships doing interstate hwy driving. Going 60 in 55 mph zone. That's 1/3 my giving me 8.875 traveling per day give or take a mile difference since I drive less on that 1 day off. Yes my Camry 2010 XLE V6 is getting 14.9 mpg and consider I live on Roosevelt Blvd so its average speed is 40-45 mph and the local streets are 25-30. It sucks but like I said the 18 year old 1995 camry V4 130 HP POS with sludge in the engine and used tires was giving me with the same half tank fill ups 22MPG because $12.60 got me 80 miles a week while my average now is $20 with 62-78 average miles. It shows in cost alone there is a huge change and the tank was the sane 18.5 gallons filled to half a tank every week for 5 years straight doing less than 5000 miles a year doing the same commute.
My apologies in advance if I sound frustrated and longwinded. I've waited 18 years to finally find a reason to let go my first car which was beyond good to me to find that, ok these cars are amazing now... faster and safer but where did Toyota's Philosophy of economical go? I love the gen 6.5 (2010)design as much as the gen 3.5 revamp design (95). But why am I getting such low mileage? I just keep getting there is nothing wrong and yet I see everyone else is fine out there. I want to fix this problem because I really have no urges to get another brand of car yet I can't rationalize accepting all these other results if I'm to stick with this car for who knows how long.
MMUK is right about the short distance driving. When I look at other cars with similar specs to mine I see a wide variation in MPG. I was not happy with mine when I first bought it in early January. I did have a bad catalytic converter which I replaced. I drive 30 miles back and forth in 4 miles increments daily with a medium number of stop lights, on top of driving a 100 mile round trip 2 -3 times a week. On the one week I made the 100 mile trip once my MPG dropped by 5-6 MPG. The range I have seen since purchase has been as low as 23 and as high as 34, depending on length of trips that week.
I still think your car should be doing a little better than it seems to be, but I've seen 4 cylinder Accords like mine getting the same mileage as you are in similar driving to what you describe.
One thing I did to test my car was to intentionally take a longer trip of 300 miles to see what the best I could get out of my car was (34MPG). Understand that I'm impatient and don't drive slow, but I set cruise at 75 MPH (70 speed limit here) to achieve that best, no hypermiling at all, just sane driving. I thought I'd made a horrible mistake at first but I'm liking my Accord better all the time.
FYI: I have only driven Camrys or Accords for the last 15 years, usually 6 to 15 years old. and always 4 cylinder engines with manual tranmissions.
Thanks for all the advice guys. I am really hoping nothing is wrong here and being that the 3 mile commute from and to work on castor ave in Philadelphia is way terrible I'll try more longer trips and full fuel ups once I get back on my feet from the first month payments done. Got the car for $19,999.00 (25,584 OM) and put down $6200 with 1.9% finance just seem too good to be true considering the 1995 Camry LE 4 cylinder was $18,000. Hope this turns out ok because It's nice to have certified used as an option for this day and age on fuel economy since I was use to $1.15 per gallon before lol.