That's great data - and exactly matches what I was expecting without hard calculations based on my experience (but mental heuristics). Thanks for sharing the exact data.

Its good also to note that the lifetime average actually slightly exceeds the EPA-instrumented estimate of 36 mpg. Its quite a feat that they managed to roughly match with the Hybrid's mpg somewhat in the Hybrid mode, despite the heavier traction battery of the PHEV.

 

Data point since the last fill-up. Drove 870 kms at speeds up to 135 kph with limited city driving (maybe 100 kms of the total) and used 52 litres of regular gas. With the remaining 12 litres, I should easily get 1000 kms on a single tank (and probably more if I drove without a brick on the pedal). Take THAT Elon!

 

Another datum: 753 km with 20 liters remaining on fill-up, this time with some slower rural driving mixed in (70-90 kph). That is 5.8 l/100 or 40.5 US MPG.

 

My 2013 RX and 2023 RX are the same way, the low fuel warning comes on very early when clearly there is quite a bit of fuel left . They just don't trust us.
As for squeezing more gas into the take after the automatic shutoff: No. Bad idea as discussed previously. When the pump automatically shuts off, my gas gauge shows the tank is (a bit more than ) full...

 

When I completely emptied the tank of our RX450h+, stopping at the first automatic shutoff put about 14.2 gallons in. A single extra fill to the automatic shutoff brought it to 14.5 gallons, exactly the stated capacity of the RX450h+

 

I am late to the party (just got a 2025 rx350h in late december 2025 anyway), and have done my own reading and research. Most helpful thing is the SAE J398 document (esp Fig B1 and the procedure for rated capacity). I am trying to upload here. The missing gap that I observed comes from top-end space (most people, me included, would stop at 1st click), and the bottom-end low fuel warning that Lexus/Toyota controls (which they revised for 2024-2025 Highlander Hybrid, and it may not be the 2.6 gal stated in the manual). J398 described that the rated capacity is determined by 3 click-offs. I don't recommend 3-click-offs, just to protect EVAP system. But now I have a good understanding of the missing capacity.

 

When I purposely ran ours down to empty, it took almost exactly the rated capacity, with a single extra click. It was only a quart short on the first click .

 

Hi, WellsB, I really appreciate the experiment you have done. It is one of the two hard data points on this topic. I obviously can't reconcile your single-click to reach full capacity with the J398 procedure. but I read your posts (at different threads), you ran 138 miles from low fuel light, which indicated 3.8 gal in total reserve (bottom end), minus the 2.6 gal per Toyota, there is 1.2 gal between low light and DTE=0. Again, thanks for the experiment.

 

If I take the average of all fill-ups at zero miles estimated range, plus or minus 16 miles, I come up with an average of 10.74 gallons or 3.76 gallons after Zero DTE. The range is from 9.9 - 11.4 gallons. I use the same protocol for filling up every time, though at multiple different gas stations in different states. One extra click after the first click.

I believe the reserve, after Zero DTE, is 3.8 gallons. I don't think that changes, only the amount that each tank takes, varying due to different gas station pumps. For the RX450h+ that leaves 1.2 gallons over the Lexus-claimed reserve at the low fuel light. One can easily drive 30-40 miles past "Zero DTE" and not even hit the Lexus claimed reserve. I figure 50 miles after Zero DTE is perfectly safe, though my average fill is at 126 miles DTE, so It's not like I routinely push it.



By contrast, my 2025 GR Corolla has a Toyota-claimed 2 gallon reserve after the low fuel light comes on and 13.2 gallons capacity. The average fill near zero DTE is 11.6 gallons and ranges from 11 to 12.1 gallons. So the GRC seems to have a reserve of 1.6 gallons after Zero DTE is reached. I believe it is very close to 2 gallons from the low fuel light.