Inaccurate fuel range indication

[Toynut]

Hello everyone, first time posting on this forum. 
I recently purchased a 2024 RX500F sport for my wife and have a question for the embers on this forum.  I understand that the vehicle has a 17.2 gallon fuel tank. I recently had a chance to notice that the low fuel indicator only came on at approximately 17 miles remaining range ( instead of 50).  I went to fill it up and could only put 12.8 gallons of fuel in it after letting click 4-5 times. I had previously brought this up to the dealership who could not give me an answer ( I thought a fuel sender calibration might be off).  BTW, the mpg indicator is reading approximately 19-20 more or less with about 1,300 miles on the vehicle.  I 

[RX400h]

Quote

The 2024 RX500 F-sport has a fuel tank capacity of 17.2 gallons¹²³. When your display indicates that there is only 17 miles worth of fuel remaining, it doesn’t necessarily mean that your tank is completely empty. Most vehicles have a fuel reserve when the fuel gauge reads empty, to prevent the vehicle from running out of fuel and to protect the engine. This reserve can typically range from 1 to 3 gallons.

So, if you’re only able to put 12.8 gallons of fuel into the tank, it’s likely because there was still some fuel in the tank. The remaining 4.4 gallons (17.2 total capacity - 12.8 gallons you added) would be a combination of this reserve and the fuel left when your car indicated 17 miles remaining. This is a common feature in many vehicles to give drivers a buffer to reach a gas station after the fuel warning light comes on.

Please note that it’s generally not a good practice to frequently run your vehicle close to or on this reserve fuel, as it can cause the fuel pump to overheat and wear prematurely. The fuel pump relies on fuel for cooling and lubrication. So, it’s usually recommended to refill the tank when it’s about 1/4 full.

 

[Carbuff2]

Get used to it...a typical amount of refuel ability IS about 12.5 gallons on the 17 gallon tank.

 

Gets talked about a LOT. 🤔

 

Personal experience: 

When filled, the DTE (Distance to empty) says ~ 410 miles. But the last fuel-gauge indicator "bar" on the gauge goes away at ~360 - 370 miles. When we fill at that point, same as you, the car only takes ~12.5 gallons.

 

++++++++++

 

Have never read an 'official' technical reason for the big reserve. Some have said that the extra fuel enables the hybrid system to run?

 

Quote

"2.6 gallons is for the low fuel light as a usable reserve (Page 519 of the manual).

Another 2.6 gallons that unusable/kept to prevent you from running below the amount to run the hybrid system on normal inclines. (Page 78 of the manual.)

17.2 - 2.6 - 2.6 = 12 gallons for the ‘E’ indication.

 

 

[cvsleeper]

2024 spec sheet states over 400 miles city and over 460 highway yet after filling the tank with 12 gallons or less the DTE shows 350 miles, false advertising or

deception?

[Toynut]

On 2/3/2024 at 9:43 PM, RX400h said:

 

I guess that the issue still stands that either the miles to empty range indicator is reading incorrectly ( overly pessimistic about range left to empty) when I theoretically  have at least 4 -4.5 gallons left in the tank, or  something ( an obstruction in the neck perhaps) is not letting me actually physically  fill the tank to it’s full capacity.  I have a Hellcat powered Trackhawk that forces me to rotate the butt of the fuel nozzle to a 1:00 O’clock position to add the last 4-5 gallons in the tank on occasion.  
In my former business life, I owned a pretty large operation of auto parts warehouses and would have annual sales of $2 -3 million in fuel pump category ( many OEM pumps fuel senders failed on domestic vehicles in large part due to the introduction of ethanol fuels in the early part of the century, so I am familiar with bad fuel senders.  
Finally, I never let my cars run to the fuel empty light lights up ( this is my wife’s car) but, it should give warning at a minimum of 40-50 miles based on her current 20 MPG.  I just happened to be driving it that morning. 

[Dean2]

Before there were electric read outs, the gauge showed empty when there was still at least 15% of capacity left. It is NOT deception, then or now, it is done that way on purpose so the general motoring public, most of whom are not very well versed in how vehicles work, don't run out of fuel. More than 80% would never twig to the fact they only take 12 or 13 gallons on empty because most have no idea what their actual tank capacity is. Ask 20 guys how to tell from the dash which side the fuel filler is on, might be 2 that can answer that.

[cvsleeper]

With our TX h, the reserve volume, fuel remaining, plus refill amount should equal 17.2 gallon time the 27 mpg should equal an DTE of 460 miles. Last fill up i only got 6.8 gallons before auto shut off. Squeezing handle multiple times hit another 0.6 gallons. Fuel gauge read 3 bars out of 4. No matter how much I refill the DTE never says 460 miles til empty  as car and driver or motor tend state in their Articles.  

[cvsleeper]

Why then do they print on their window sticker 3.7 gallons per 100 mikes car and driver using Lexus specs state 460 plus snd motor trend stated 460 plus. If these gallons are unusable, correct specs sheets and do not deceive customers. I filled up with 88 miles on DTE able to put 9.6 gallons got 3 bars on fuel guage. Snd new DTE of 340. 

[zazaa]

On 2/3/2024 at 8:51 AM, Toynut said:

Hello everyone, first time posting on this forum. 
I recently purchased a 2024 RX500F sport for my wife and have a question for the embers on this forum.  I understand that the vehicle has a 17.2 gallon fuel tank. I recently had a chance to notice that the low fuel indicator only came on at approximately 17 miles remaining range ( instead of 50).  I went to fill it up and could only put 12.8 gallons of fuel in it after letting click 4-5 times. I had previously brought this up to the dealership who could not give me an answer ( I thought a fuel sender calibration might be off).  BTW, the mpg indicator is reading approximately 19-20 more or less with about 1,300 miles on the vehicle.  I 

I purchased a 2024 RX500h F sport and have notice the same fuel gauge issue.  When low fuel indicator light comes on I have 20 or less miles left in tank as listed on miles to empty.  But when I fill the car up with gas it takes 11-12 gallons and I have travelled only 273 miles.  Tarhis has happened several times.  I took the car to the dealership and they did a software update but that didn't work.  It is very annoying to have 5 gallons and over 100 miles to go left in the tank when the low fuel indicator comes on.  Lexus can do better and needs to fix this issue

[Toynut]

I agree that there is either a software issue or  a problem in the filler neck that prevents a complete fill ( my Jeeps make me upend the pump nozzle to add the last 3-4 gallons on occasion).  This Lexus is the first Toyota product I have purchased since the 80’s and plan on a GX 550 overtrail when they release a hybrid version.  This issue, as  well  as the fairly low fuel mileage is not exactly comforting. 

[Toynut]

Interestingly enough, some of the YouTube videos indicated high 20-low 30 ish mpg in their videos ( mostly California videos). 

[Dean2]

You guys do realise that with the fuel pumps in the tank they need to have fluid on them to prevent overheating, and you have to have enough fuel that if you are on a steep uphill, it can still pump fuel. If you run them low enough you will potentially stop, even though there is gas in the tank.

Old cars had mechanical or later, electric outside fuel pumps. You could run the tanks nearly empty on flat ground becuase the fuel line came out the bottom of the tank, but even those were uphill sensitive. Modern cars with in tank fuel pumps aren't like that.

[Toynut]

I am aware of in tank fuel pumps.  I don’t jump on the gas in my Hellcat powered Trackhawk without at least a half tank of fuel to prevent a lean out condition upon acceleration.  The factory calls for 2.2 gallons left in the tank before the refill light goes on.  This has not been the case with mine ( and apparently others on this thread).  Safety margin aside, the vehicle is at least 3-4.5 gallons short of a full tank if the 2.2 gallon lower limit is reached.  When the dealer handed us the new vehicle with a full tank of fuel in it, the MTE indicated somewhere around 450 miles.  Every subsequent fill up is off by 100-125 miles or more. Something isn’t adding up, no matter how it’s calculated. Even with the mediocre 20-21.5 mpg indicated, the MTE should trip at 45 mile range or better, and not at 17, if there is a fuel level sensor that is calibrated to light off at 2.2 gallons in the tank.  Can’t seem to get more than a head scratch from the dealer tech.  The car is not driven aggressively in our suburban environment.  I haven’t had it on any long trips yet, but I am curious if there will be a substantial improvement or when the weather warms up come late spring. 

[Dean2]

Put a 5 gallon jerry in the trunck. Run it till it stops. Add the 5 gallons go to station and fill up. You will pretty soon know if you are getting a short fill or there is way more than 2.2 gallon in the tank when the light comes on.

[Lexus-CT]

I am not counting gallons and miles, but whoever say that Lexus and Toyota are optimistic in their ads when telling that fuel economy is excellent. Most other companies are doing likewise.

The little CT we have was adverticed with a fantastic fuel economy.

3.8L/100km

Reality after several years of refilling the tank is quite a lot different

6.7L/100km

Lexus service personnel say it is normal. Nothing wrong with the car, hybrid battery is controlled yearly.

Compared to the VW Golf 2.0tdi DSG it is not as expected cheaper to drive as the diesel was using

5L/100km

and diesel is cheaper. Same driver – same driving style – same area.

I think that the extra battery in the car is not getting better fuel economy out of the car, just making the car consumes tyres a bit more than if the extra (hybrid) battery was not in it.

 

[Carbuff2]

The 5 gallon 'reserve' has been noted and discussed on many Gen-5 RX forums and FaceBook groups. 😒 The tank is shallow and horizontal, it runs along the left side of the chassis.

 

One guy DID run the RX to empty (and refilled from a can to get to a station).

 

We have difficulty running more than 350 miles on our 500h.

[loopbloke]

We just bought a 2021 Lexus RX450h and has been getting only 370 mile range on full tank.

[Screwball]

I think we need to keep in mind that the miles remaining readout is only an estimate calculated by the car's electronics based most likely on your average mpg over a certain (unknown) period of time, and the fuel pump's best estimate of the remaining fuel that's sloshing around in your fuel tank minus the emergency fuel buffer of at least a gallon. My Jaguar has the same issue. I think miles remaining readout is just a conservative estimate at best.