2016 3.5 TI-VCT with 90K miles - After the past three fillups the Miles to Empty display has read 392, 360 and this after this morning's fillup 342, Anybody have this happen? Reason for concern?

 

It’s a math calculation but the variable is your mileage per gallon at the time. Unless your mpg is the same, your distance to empty will be different.
My DTE varies every time that I fill up but is much more when I’m towing my travel trailer and when I’m not. Make sense?

 

It's never going to be the same between fillups, and it won't track exactly with your odometer mileage, because the DTE reading is predicting the future using data from the very recent past. It's a reasonable estimate and not intended to be exact. When I fill my truck with the big tank, it will predict the DTE is anywhere between about 500 and 640 miles, depending on my recent driving.

 

I can pull my travel trailer for 200 miles, use 1/2 tank getting 10 mpg. Reset everything under various menus, drive the next 100 miles at 70 mph interstate (no trailer) getting 20mpg. stop and fill up. DTE is somewhere between 300 and 700 miles. After 5 years of ownership I have never understood how dte is calculated, it changes at random over time in truck, and after long interstate runs, avg 20 mpg, if it says 50 miles left, my 36 gallon tank should have 2-3 gallons left, and take 32+ gallons of gas. I'll fill up, it'll take maybe 28 gallons. My point is, dte is as accurate as licking your finger to determine wind direction. My 05 Yukonxl was far superior technology. The gas gauge in general seems accurate, and I monitored mpg over a year, (gauge vs manual math) adjusted for error, and it tends to be pretty accurate over time.

 

DTE is based on your most recent driving, and 0 isn't when your tank will use the last drop. When DTE gets to 0 you still have a reserve of a couple gallons left. Resetting your displays doesn't change the DTE algorithm; it's not like clearing a desk calculator. Your mpg display can be calibrated for very good accuracy - mine was consistently within .1 mpg of my hand calculations, before I stopped bothering with hand calculations.

 

maybe my post didn't display correctly on your end, I would think after driving 100 miles on hwy, that would be adequate for recent driving activity, and my next fill up and dte would be based off that as you suggest. And, I did mention I have my mpg fairly accurate after a calibration, and I also no longer concern myself, it's pretty decent even between extreme mileage between towing and regular driving.

 

It does, thanks!!

 

Unfortunately we don't know the algorithm or which data sets are involved. All we know is, it's a snapshot which will vary with current conditions and recent history. In my work, I do calculations regarding estimated remaining service life of various components; in every report, the result varies, and someone always asks why a year later it's changed by more than a year one way or the other, and I have to explain our methodology. It's just an estimate for planning purposes and nothing to be concerned about in the short term.