wrinkle

I suppose this is generally a unique problem with PHEV ownership and usage, especially those that have 40-50 miles of pure EV range that cover regular/daily use around towns and cities. So that leads to very sparse use of the actual gas in the tank, leading fuel to stay in the tank very long, statistically much longer than any gas car. Factor in the fact that the RX450H+ and NX450H+ are full-bore hybrids being quite fuel-efficient, leading to very few fill-ups at the pump. Now of course, that's a good problem to have

At least I'm in the above camp, almost forcing myself to use the gas engine (during regular commute when at higher speed), so that I actually use up the gas gradually and use the gas engine some too. I drive at least 100 miles per week overall. This article states that gas can go bad in 3-6 months, and suggests the use of fuel-stabilizers as a method to prevent gas degradation. Even if I'm using the gas engine some, if I follow the advise of the topping off the gas tank to limit moisture and oxygen in the tank - that would imply even longer periods of not re-filling gas.

How have others dealt with this - is there any argument against fuel stabilizer use ? Any specific fuel-stabilizer brand recommendation ?

LeX2K

STA-BIL claims to work for 24 months I use it for cars I store over winter. Does it do anything? Don't know but it's cheap potential insurance. Gas doesn't go bad in 6 months not in my experience.

asj2024

Tank is pressurized (which is why if you look at the manual it says the cap won't open immediately), which helps preserve the fuel.

I also keep fuel tank low in gas (only 200-300 mile range total) until I go on one of our longer trips, then I fill it up so range goes to nearly 600 miles.

Dhill

Per the RX 450h+ manual, Lexus recommends adding 5.3 gallons over a 12-month period. You will also get a warning if new fuel has not been added for a long period:

Carbuff2

Lexus' recommendations are all you need. Add Sta-Bil if it helps you sleep at night. That article regards 3 - 6 month degradation of fuel is kind of alarmist IMO..but adding Sta-Bil is encouraged at the collector-car storage facility near me.

Some folks say that keeping fuel LOW in the tank encourages moisture build-up. Don't know how Lexus' EVAP system handles that, it MUST allow SOME pressure balance even if the fuel cap isn't opened during an entire tank.

wrinkle

Sounds like adding STA-BIL is not known to cause problems at least - even if its efficacy is undetermined.

The thing I'm being careful about is that the product life-cycle of PHEVs with 40-50 miles (or up to 100 miles, say) pure-EV range is actually very new in the car industry overall - even compared to pure EVs that have existed for decades now. So corner cases of reliability management may not all have been exposed across the population yet. And despite Lexus/Toyota's conservative designs - we know they screwed up with the 12 V battery management design in the 2nd Gen NX and the 5th Gen. RX quite a bit - and still haven't fixed it in the field despite its existence from NX owners complaining about it since 2022. And we now have hard data in the forum about the underlying reasons for problems in the 12 V charging subsystem. After facing the 12 V battery charging issue in my RX with regular/reasonable use, I have figured that Lexus doesn't really have all the reliability bases covered in their design. That is the reason I got thinking about the potential fuel degradation problem (that doesn't exist for gas or pure EV cars that are used regularly).

In California, you can't buy ethanol-free gas, which creates many of the moisture/corrosion and related fuel-going-bad problems by my readings. I guess I will keep fill up lower than half-tank generally and consider STA-BIL in the longer term.

WellsB

I've left gas in my motorcycles, in California, with E10 gas and no stabilizer, for over a year without issues. They do run a bit smoother and have a bit more oomph after refilling with fresh fuel, but there are no starting or drivability issues on the old fuel. All are fuel-injected with pressurized tanks, similar to the RX450h+ tank, though I imagine the RX tank is even more vapor tight. Even my lawn-mower, with a non-pressurized tank, has had gas left in it over the winter, and it starts on the second or third crank the next spring. The only engine I have that is particularly sensitive to gas age is my 1,800-watt inverter generator. I've learned that it needs fresh gasoline, less than a few months old, so it gets completely drained at the end of the fire-season and gets fresh gasoline for its first use of the following season. If I put older gas, even with Stabil in it, in the generator, it starts fine, but surges constantly until fresh fuel is put in it.

LeX2K

"quality of fuel has changed' Lexus lawyers stepped in can't say "fuel goes bad".