I should have consolidated these thoughts, but if you remove those extra 1.5 gal I do after the back press cuts off, that puts me in the range (around 14 gal) that others are experiencing for a fill up. So allowing for an approx 1.5 gal remaining at “0 range” (40 miles additional range?), maybe the gas tank is 17.2 gal as advertised??

 

My 2024 TX500H has 61,000 miles on it and whenever I filed the tank, its never taken more than 12.5 gallons. I never trust that there's an additional 4 gallons in the tank - ie about 17 in total.

Also on milage I never got more than 25 mpg.

 

My 2024 TX500H has 61,000 miles on it and whenever I filed the tank, its never taken more than 12.5 gallons. I never trust that there's an additional 4 gallons in the tank - ie about 17 in total.

Also on milage I never got more than 25 mpg.

 

Could there be some type of "burping" issue, perhaps related to the environmental equipment. This happened on the Chrysler Aspen/Dodge Durango.

 

What would be the basis? That you could drive longer without running out of gas?

Personally I think the small tank is a major design defect but it is one that is disclosed (though I'd imagine most consumers, including myself, don't notice) and isn't a safety issue. It greatly annoys everyone but unfortunately Lexus made a conscious design choice, no doubt to save a few pennies, rather than make consumers happy. I would certainly mention it any time I see a Lexus senior executive (never) but I'm sure they could care less as long as the profits keep rolling.

 

2026 Lexus TX500h Luxury, here. Had the car since late November and have filled it up twice. Each time it easily took 16 gallons after the LOW FUEL warning came on at 7 miles of range indicated and I probably could have topped it off to put in more. At fast fill, the (COSTCO) gas pump clicks off at about 14.75 gallons the first time. Then I do a slower fill to about 16 to 16.1 gallons, No fuel is visible in the cars filler neck afterwards. And the car runs fine.

The gas tank is long and roughly cylindrical and of course it has baffles - they ALL do to prevent major fuel slosh when driving. (~120 lbs of fuel can REALLY rock the car back and forth when the level drops below full if not moderated by baffles). This does not decrease tank capacity but it CAN require a slower fill rate on some cars. And as it approaches full, fuel vapor pressure rises faster in the tank as empty space disappears and causes the gas pump nozzle to sense this and click off at high fill rates. So the last gallon or so should be done at a slow rate. Note that this is NOT "click-clacking" the filler nozzle until fuel fills up to the top of the filler neck. Never had a car damaged by a final slow fill - not the charcoal canister, not the catalytic converter, not anything.

The manual rates the TX 500h fuel tank to hold 17.2 gross (not usable) gallons and being able to use 16.1 gallons out of that is pretty darn good. Most of my cars have needed at least 3 gallons in the bottom of the tank beyond rated capacity to function reliably, with one (1) notable exception ( a Ford Expedition). Lexus says in the manual 2.6 gallons are needed for the TX 500h. But apparently the TX 500h does just fine with 1.1 gallons in the bottom, if I believe the fuel tank rating and MY results - or perhaps the rating has a small undocumented reserve, maybe in the lower filler neck, that increases capacity slightly beyond 17.2 gallons. Or not. Who knows?

BTW - the cars in-tank fuel pump has built in filters and there are others downstream - no solid trash will get into your fuel system and this filter is very resistant to clogging unless you use heavily contaminated gas. Water being the most troublesome contaminant - though 10% ethanol fuel blends tend to clear this out (they absorb water - used to be called "dry gas").

Note also that the electric fuel pump is cooled by fuel flowing THROUGH it, no so much surrounding it. Which is why having it suck air for an extended period, which can happen when the tank is VERY low, is not a great idea. But as long as it can gulp fuel, its OK. And air in the pressurized fuel system can cause operation "glitches" as well - so running out of fuel in a fuel injected car is not a good idea, either. Still, these systems are pretty well engineered and robust. They don't break very often (I've only have had ONE tank mounted fuel pump replacement in decades, and on a 22 year old classic exotic car).

Sounds like Lexus may have reprogrammed the fuel gauge firmware earlier this year to have the low fuel warning come on later, based on other social media comments. Whatever they did, the system in my car seems to work fine. Ironically, in about 2020, Toyota issued an update for the Highlander fuel gauge firmware due to owner complaints of insufficient fuel reserve when on empty. Earlier complaints about the TX was that the reserve was too much.

 

While I am new to the Lexus/Toyota family I have been around cars for a long time.

One thing I have learned with modern vehicles is that once the fuel pump clicks off you should consider your tank filled. I say this because some manufacturers have their environmental systems close to the filler nozzle. "Overfilling," or adding more fuel after the pump has clicked off, may cause fuel to spill into these environmental canisters/equipment and subsequently may cause damage to the fuel system or environmental control system. This is known with late model Cadillacs for example. While it may not be an issue with our vehicles (or it may be) why chance it?

 

Fast filling at a gas pump will invariably underfill the gas tank due to early nozzle click off. So if you want to be able to use full tank capacity, slowing the fill rate is necessary. This is very different from topping off to the top of the filler neck and resulting in a possible spill.

I've had dozens of cars and never damaged any by doing this.

Your choice. But please don't complain a fuel tank can't be filled to advertised capacity due to a defect if you, the operator, refuse to fill it properly ... and don't realize the last 1 - 3 gallons are generally not usable (varies by model).

Same goes for cruising range. Never believe a range calculated based on the gross rather than usable tank capacity. Nominally, the maximum safe and usable range of a Lexus TX 500h Is about 17.2 - 2.6 gallons (per the manual) x 28 MPG = 409 miles.

 

Most listed fuel tank capacities are in gross (total) rather than usable gallons. Generally, the last 1.5 to 3 gallons in the bottom of the tank are not usable. For my Lexus TX 500h, the manual states that at least 2.6 gallons must be left in the tank for reliable operation (on hills as well as level ground).

Still, mine seems to do a bit better - I'm able to easily put 16 to 16.1 gallons into a 17.2 gallon tank after the low fuel light comes on AND range has gone to zero, which would means that there is only 1.1 to 1.2 gallons left in the tank (maybe its bigger than 17.2, despite the rating?)

I generally fill the tank at full speed (handle latched at top auto-fill notch) until about 14.75 gallons, where the pump "clicks off". I then do a slow fill on the bottom auto fill latch notch where the pump generally stops at around 16 gallons. I do not "top off" beyond this fast/slow fill (no "click-clacking the pump handle) and there is no fuel visible in the filler neck nor any spill when I'm done.

I've never damaged ANY car doing this (fast/slow fill) and have always needed to do this to get reasonable capacity out of the tank. Including our 2010 and 2023 Lexus RX350's, my 2026 lexus TX500h, my old 2008 Toyota Sequoia Platinum and many more non-Lexus/Toyota cars.

You're doing OK. 17.8 - 15.6 gallons means about 2.2 gallons is left sitting in the tank. If you check the "If you run out of fuel" section of your user manual, you'll find advice to put at least 2.6 gallons or so in to "limp" to a nearby gas station.

 

Good luck with your fuel tank capacity problem. We have a 2024 Lexus TX500h that was diagnosed by a Field Tech Specialist with a deformation of the fuel tank. The "FTS" is the Lexus expert/specialist for diagnosing problems the dealership can't handle in the service department. This person is a regional Lexus support service expert. The maximum capacity of our gas tank is 13 gallons. We do not run it to 0 miles DTE but to the point that it might have 20-30 miles DTE. If you run your car past 0 miles, I'm sure Lexus will not warranty your car because you might or will eventually damage the fuel pump that needs the extra fuel to work properly. The FTS was assigned to our car and diagnosed our problem in early February 2025. This only happened after I told the dealership service department repeatedly for 9 months that we had a fuel capacity issue. We also kept extensive records about fill ups and mileage I continuously contacted the Lexus Engagement Center. The FTS wrote that the car had a deformation of the gas tank and would need a new redesigned fuel tank. After continually calling the Executive Lexus Engagement Center for months to get an update on the new gas tank, I was told that there would be a fix in December 2025. It has been over 10 months since the diagnosis. We have had the car since April 2024. This problem has existed for 22 months. Obviously, Lexus feels that there is no urgency to fix the problem. It is very misleading to think that you have a gas tank with 17 plus gallon capacity and you can only fill up to 13 gallons. Obviously, this becomes a range issue when taking long trips. Lexus knows they have a problem. Lexus needs to address the issue or change the information on the sticker and anything that has printed information about the car's capacity One way to cure the issue is to let people know the real range of the car. This would be similar to approximate MPG. Once again, good luck with your capacity issue. Please keep the forum posted. I'm interested how you are going to handle the fuel capacity problem.

 

I run past zero every tank in every Toyota vehicle we have and did the same in the Lexus vehicles we had.

If they are labeling this as deformation of gas tank then it’s across the board. I’m currently on a road trip and I ran 35 miles past zero in my Tundra. I’ve been doing it for years. It’s the biggest pet peeve I have with Lexus/Toyota.

We have a ‘23 RAV4 hybrid and family member ran it dry and my guess tried restarting it which shut down the hybrid system. Had vehicle towed to dealer where they had to put techstream or whatever their computer is called on it to clear the error codes. Warranty was not voided. SA diagnosed it as “big dummy” and sent us on our way.

I say that to say it’s how Toyota/Lexus programs their DTE. Now I do recall 2019-2020 RAV4 hybrid having fueling issues where owners couldn’t fill the tank but not sure what was the actual cause and fix.

Interested to hear if Lexus replaces your tank. Please report back any updates.

 

Note that the Lexus TX fuel tank is rated at 17.2 gallons gross (not usable) capacity. You are able to put in 13 gallons with 20-30 miles of indicated range left, which is about 1.5 gallons of fuel unused. In addition, Lexus states in the "if you run out of fuel" section that 2.6 gallons of fuel is needed in the bottom of the tank for reliable operation and it makes a great deal of sense that they would tend to set the predicted zero range point at that level. If we do the arithmetic, 13 gallons fill + 1.5 unused + 2.6 minimum to operate reliably = 17.1 gallons, which accounts for all but 0.1 gallons of rated tank capacity. Thats pretty darn close, even allowing for some +/- error in estimation.

So ... Perhaps your lack of tank capacity is the result of how you fill the tank (not quite full), when you decide to refuel (not quite empty) as well as a conservative Lexus range prediction - ranther than a damaged/deformed fuel tank.

Note that a tank defect or damage that reduces capacity by 20% should be pretty obvious in inspection and that it would likely represent a major safety hazard from potential leaks if compromised that much, in my opinion. Either you or the dealer would have to act immediately to address this potential safety issue - because the liability and danger could be enormous. BTW - the TX uses a plastic fuel tank - they don't permanently deform very much before they're compromised - not like the old steel ones that could be significantly dented and still not leak.

Another thread mentioned a 2025 TX TSB that corrects overly conservative range estimates and low fuel warnings that some owners have complained to Lexus about. Perhaps that's why I can easily put 16-16.1 gallons into my TX 500h tank without topping it off (but using a slower fill rate for the last 1.2 gallons) after running it to zero remaining (indicated) range. The car was delivered to me in Novenber of 2025, BTW. I suggest you enquire (perhaps at another dealer) to see if this is available to you and your 1st year (2024) Lexus TX 500h. It might help.

 

I've been dealing with the same issue for some time ('24 TX 500h, now 19K miles)... and accepted this reserve capacity explanation. HOWEVER, my range miles total has been DECREASING over the past year. How does that get explained? A year ago, when I filled my tank it said ~320 miles of range, and it's been getting lower and lower.

As of today, it's stating 275 miles full tank range! I was on the low fuel warning, (supposedly) 15 miles of range left. At the gas station it would only let me add 10.7 gallons of gas (and that was ignoring the first click off of the pump nozzle for a bit). And again, according to my TX 500h, I have 275 miles of range. Even if you accept the intentional gas reserve explanation, why has my full tank capacity dropped from 320 to 275 miles? Something isn't right.

 

Note that, per the 2026 manual, the gross fuel tank capacity of a Lexus TX500h is 17.2 gallons, vs. 17.8 on the Lexus TX350 and just 14.5 gallons on the Lexus TX550h+.

A car's computer generally calculates remaining range based on cumulative MPG history x the safely usable gallons of fuel it estimates is left in the tank. If your MPG has been dropping due to changing driving mix (as in a change to many short "start from cold" trips) or cold winter weather, MPG will drop resulting in a shorter estimated driving range.

Has your MPG been dropping as well? Has your driving mix changed?

Based on my experience with my 2026 Lexus TX 500h Luxury (late november 2025 purchase), you should be able to safely put 16 to 16.2 gallons of gas into the tank when the guage shows zero range ("REFUEL NOW"). If not, there may be a TSB that's applicable to your car that has an update to the gas guage and low fuel warning system - but from what I've heard, an owner has to ask for this update. My car, being newer, may already have this update. Because I'm putting in about 94% of my tanks stated GROSS capacity, leaving just 1 gallon sloshing around in the bottom, and I have NO idea how much of that remaing fuel is a usable "reserve" (this probably depends on the angle of the road the car is on, temperature, etc.).

Another possibility for "short fueling" is the gas pump and nozzle you're filling your car from. These are hydro-mechchanical devices and are NOT terribly accurate or repeatable from nozzle to nozzle when it comes to sensing "full" and snapping off. There are a LOT of variables to consider, from mechanical tolerances to pump fuel pressure to temperature to tank and filler neck construction (restrictors and baffles). Auto shut off sensing is largely driven by sensing the rate of rise of vapor back pressure in the tank. As the tank approaches FULL, vapor back pressure rises faster. So if the nozzle shares a single fuel pump with another nozzle (most do) and another car's nozzle "clicks off", it will often cause a pressure surge in the nozzle fuel line that can cause your's to click off as well because it "looks" to the nozzle like a surge in tank vaport pressure.. And if you are the sole user of the gas pump, the fill rate will be higher and the nozzle with click off sooner to begin with because the vapor pressure rise (and tank fill rate) is faster to begin with. And to make this variability even WORSE, gas tanks in different car models are usually built with DIFFERENT arrangements of internal "anti-slosh" baffles and nozzle restrictors - so the back pressure the filler nozzle "sees" at any fill point will usually vary from car model to car model. Even from TX350 to TX500h to TX550h+ - they have different gas tank capacities, after all.

So - what to do? I've tried multiple nozzles at multiple gas stations and found that with MY TX 500h, I can generally put in 16 gallons on average AFTER "REFUEL NOW" flashes up over the gas guage without overfilling the tank and with zero spillage or bad behavior by the car - simply by doing a slow fill after the nozzle first clicks off of fast fill. Some gas nozzles will click off 0.5 gallons or so earlier, some 0.5 gallons later - but its generally in the range of 13.75 to 14.75 gallons at first click-off (yes, I'm keeping a spreadsheet). And then a slow fill to about 16 gallons.

My (unprofessional, personal opinion) recomendations:

1. Figure out if your MPG has been dropping and why (cold weather, many more cold starts and short trips, etc.). If it has been, this is likely why indicated range is dropping as well.

2. Experiment with how you fill your gas tank and determine that it's "full". Going "over" one ot two times to figure this out will not likely harm anything, IMO, or there would be a LOT of dead cars at and around the gas pump or failing smog inspection. (NEVER had this happen in decades of driving MANY cars). Make sure the fill rate AFTER first "click off" is S L O W. If there is less than 16 gallons of usable fuel in the tank from start to finish, your TX500h behaves VERY differently from mine. WHICH IS POSSIBLE. See thought #3, below.

3. Holding thought #2 above, visit the dealer and ask about a TSB (Technical Service Bulletin) relating to excessive reserve/poor range on your TX 500h. If they have no idea what you're talking about, try another dealer. Unlike RECALLS, TSBs are generally not considered a mandatory "must fix" by the dealer and Lexus. They may or may not be done at the discression of the service center.

Good luck with this and please let us know how this works out.

 

Nope. My mpg is averaging 19-20 still (always has been below 22). No change in driving style or mix of city/highway. And the most I've been able to add to my tank is 11 -11.5 gallons in recent months, and that's when the low fuel warning is on and it shows 15 miles or less of range. I do the same regarding squeezing another half gallon after click off. It's the weirdest thing. I guess at this point I will have to take it into the dealer and see what they say about any related TSB.