Why does it need any fuel to start the hybrid system, it is battery operated, has nothing to do with fuel? I thought the ICE doesn't kick in until 30-40 mph. You don't need 5 gallons to start the engine. Toyota's explanation sounds a little funky.

 

If the hybrid battery is depleted or it is cold out, or you floor the gas pedal, the ICE will come on immediately. The hybrid system once the ICE is warmed up will work in addition to the ICE at the same time. If you are on flat ground or going down a hill or are sitting in traffic, the ICE will shut off until the battery gets low. If you run the heater the ICE will always be on. If you run out of gas, you should turn off the ICE ASAP or it will be very hard to start the car if you completely drain the hybrid battery. If you run out of gas, the maximum you could drive is 1 mile and that's if you on flat ground. Plugin hybrids are different and they would allow you to drive several miles to a gas station on empty.

 

If the traction battery is completely depleted, then the engine can't start, and there is no easy way to charge the traction battery outside of the hybrid system, except with the RX450h+. I assume that the dealerships have some way of doing it, but that is just an assumption.

My assumption of the way the hybrid starting system works when the fuel tank is empty(partially based on running an RX450h+ out of gas);
The hybrid system attempts to start the engine.

The engine fails to start after a certain number of attempts or time spent trying to start the engine.

The system stops trying to attempt to start and won't make another attempt until it senses that there is fuel in the tank.

Because Lexus lists the reserve at 2.x gallons (varies by model) the same reserve amount is given as the amount needed for the system to attempt starting again. I believe, to ensure a start attempt, one needs to actually put in enough to register in the computer. I don't know if that is less than amount it takes to register as more than empty on the fuel gauge, or if the sending unit is still registerering fuel level when below "Empty" on the gauge.

I don't believe that there is a separate "reserve" to protect the hybrid system.

In the case of the RX450h+, which I have run to true empty, the reserve is about 3.2 gallons, compared to the Lexus claimed 2.2 gal. I'm afraid I did not experiment to see how much fuel it took before it would start. I just filled it up completely and then it started with no issues. It took the Lexus claimed 14.5 gallons without undo "topping off." I filled it at full speed until it stopped automatically, then continued pumping at half speed until it stopped again. It did set codes when it ran out if gas. I reset them with an OBD2 dongle.

In the case of the RX450h+, after the tank is run completely empty, the hybrid system attempts to start the engine, fails, codes are set and the hybrid system will not attempt further engine starts, the vehicle will continue to move as long as there is enough power in the traction battery. I assume it would stop moving when the traction battery reaches around 12% which is when the vehicle switches to hybrid mode, but I did not test that, for obvious reasons. I don't know if the RX350h and RX500h would continue moving if the engine won't start. Regardless, even if it did continue moving it's unlikely it would get you to a gas station and I'm sure it would shut off at some minimum point before complete depletion of the traction battery.

If I were to run one of the other models to empty, I'd plan on needing at least 5 gallons to restart it.

 

Then I would think Toyota should advertise this vehicle as having a 14.6 gallon fuel tank not 17.2 if you can't use the other 2.6 gallons. I assume the dealers or the manufacturer would have to fill at least the 2.6 prior to delivery or the transport operators would not be able to get it off their trucks. Not all of those vehicles are level on the truck. If the dealer lets someone test drive your vehicle prior to pick up it would have to have that 2.6 gallons in it already plus some more or the vehicle would be shooting codes at the person doing the test drive. That wouldn't go over well.

 

Just to be clear, the engine will start as long as there is usable fuel in the tank. It's when the tank is run completely empty that the protective feature kicks in. That prevents the traction battery from being completely discharged, which would require the vehicle being transported to a dealership to rectify.

My understanding is that vehicles are shipped with several gallons of fuel, plenty to get them on and off of transportation and moved around lots before getting to dealers.

 

So if someone runs out of gas in their hybrid, can the AAA service guy just bring you gas and start the car? It was said above that they would recommend putting at least 5 gallons in the empty tank. I don't think the road side assistance guys usually bring that much. Do you also need a scan tool to clear codes to allow it to start? It seems starting an out of gas hybrid may be more of a chore than a normal ICE. If the traction battery gets completely drained, does that mean a flatbed to the dealer?

 

You don't need a scan tool to start it, just to reset the codes.

I suggested 5 gallons as a conservative amount that should always be enough to start the vehicle. I don't know what the actual amount is. It may be less. A quick Google search indicates that wrecker services will provide 2 gallons as a default, but up to 5 by request. If they don't carry enough, then they could tow you to the nearest open gas station.

If the traction battery is completely depleted then yes, a trip to a dealer would be required.

 

I agree with you 100000%!!! Lexus should have advertised 14.6 gallons instead of 17.2! All of my other cars are able to fill up to the advertised gallons. Who would have thought buying the RX350h advertising 17.2 gallon capacity only allows you to drive about 12 gallons to refill? I did not expect to go to gas stations as often.

 

Not sure what vehicles you've owned before, but every vehicle I've owned that has a low fuel indicator has taken less than the advertised amount to fill up, usually 2-3 gallons less. Even the vehicles I've had that didn't have a low fuel indicator have had fuel left when the gauge reads empty and take less to fill up than the rated capacity.

Rated capacity is the amount of usable fuel in the tank, not the amount that you can put in when the fuel gauge reads empty. I have proven that the RX450h+'s usable fuel capacity (14.526 gallons) is extremely close to the rated capacity of 14.5 gallons. I can only assume the other model's rated capacities are similarly accurate.

The issue here is not that the advertised capacity is wrong, but that the fuel reserve quantity stated in the manual is wrong. The reserve can be used, you just don't have a gauge or Miles Remaining to let you know exactly how far you can go.

 

I have a 2024 500h and have the same results. With refuel light coming on I have travelled about 280 miles. Average MPG is 23.5. This has been consistent with our first three fill ups. Took it to dealership and they did a software update on vehicle which didn't help. I can't believe Lexus doesn't fix this problem. Very annoying.

 

Our 500h is annoying too.
I have to fill up every week because my wife refused to drive if the gas light is on. It takes around 11ish Gal each time.

 

My 2024 Rx350h, will read for example 1 bar left in the fuel gauge, and 58 miles range, but when I fill up, only takes 10 gallons. Is this a common occurrence for this vehicle or a bad sensor?

 

Ours just took 11 gallons while on 1/4. It was the first fill-up we did.

 

Common complaint. For most, running the gauge to EMPTY only allows 10 - 11 gallons of fuel.

https://www.clublexus.com/forums/hyb...fuel+capacity+

 

I know that in my Prius, the official capacity is 11.9 gallons (45 liters), which would have given me a range of around 600 miles (965 km) , but I can only typically add 9 gallons or so (34 liters) to an "empty" tank.

This would be about a 20% reservoir buffer, so it's a liberal reservoir. Reservoirs more than that should be recalibrated to allow more range.