2020 Tacoma TRD OR AT 4WD dash shows only 280 mile till tank empty. is this normal?

Yes, but when the instrument panel is telling you your range, it's not going to give the range for running the tank dry. It's going to give a "safe range", where even if owners exceed it by 20-30 miles, they still won't run the tank dry.

Because if Toyota did give the displayed range as the "tank dry range", you'd have people thinking they could go right up to that value before they started looking for a gas station and then they'd complain because they ran out of gas.

that's why my original post mentioned an 18 gallon capacity with a "couple more gallons for wiggle room". ~18 gallons is the "practical capacity".

 

Yes, I agree... but capacity means just that, so a disclaimer is warranted for those of us who are not stupid. I did lots of study on the gas gauge needle position and the low fuel warning light... stopping to fill the tank at various points. Now, my truck is a 2010, but as far as I know, the tank size has remained the same. Toyota just added a computer to do the thinking for you.
For the geeks who like details of actual fuel measurements rather than some computer estimate with a safety cushion:

The following figures are +/- 0.5 gallon as temperature and other conditions will change the volume of gasoline as well as where you stop filling the tank.
FULL: 21 Gallons
3/4 Line: 16 Gallons [5 to fill]
1/2 Line: 12 Gallons [9 to fill]
1/4 Line: 8 Gallons [13 to fill]
Low Light: 4 Gallons [17 to fill]
Empty Line: 3 Gallons [18 to fill]

*Do your own research to see if these numbers work for your Tacoma, too.

 

Nope. I can squeak out nearly 400 miles. ~18 gallons at ~22MPG or so. This would be a nearly full tank at 65-70 with minimal stopping. 3.6L with the 6 speed. The auto gets better mileage due to its better highway gearing.

I actually get my best gas mileage at about 40-45 in 5th or 6th. Display usually shows a consistent 30 instant MPGs on flat ground.

 

I am getting about 16 miles to the gallon city driving which is most of my miles so far. New 2021 Pro and now have 600 miles.

 

And seemed to get a bit less gas mileage on the Costco Brand gas vs. my last tank was Shell.

 

Too much whining and discussion about "Distance to Empty."
When the fuel gauge gets to the "E", fill the damn tank.

 

LOL, right? OR SOONER!!

 

I only use shell.

 

I think they may have pushed a borked software update. On a full tank, mine always showed 380-390 mile range. I did a double-take a week or so ago when it started saying 256 mile range with a full tank. Based on my actual, measured, fuel consumption I'm good for 308-370-ish miles depending on the conditions.