Reserve Fuel Capacity

[malcolmw]

Here's a bit of useful information about the 4th Generation RX450h.

I have run the range reading down to zero just at the point of refuelling. It took 58 litres to the brim thus leaving 7 litres left in the 65 litre tank. This residual is equivalent to 1.55 gallons. If you reckon on 30 mpg, this gives an emergency range of about 46 miles.

You never know when this might be handy to know. 

[ISJason]

Thank you for posting that info.

In my RX 400 I have always filled up when the needle has gone down to just at the top of the quarter mark , as I was a bit worried about how much fuel I had left in after that. But recently I let it run down a bit more until the needle was on the white mark just above the R ..and the red light still hadn't come on, so the capacity is better than I thought.

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[GSLV6]

I never, ever, run a tank down that low, as any cr*p in the tank has more chance of getting through to filters and blocking them, plus you're not really left with a 46 mile safety net.  When they set the empty mark (or "zero range") they do take in a factor of safety where the minimum amount of fuel to prime the fuel pumps and to be able to swill about in the tank without inducing air into the feed, are all things accounted for, so a 65 litre tank isn't really intended to give a 65 litre range, I'd guess more like a 60 litre range.  Depends how you drive your car and the terrain it goes over  (ie uphill with a fuel feed at the front of the tank = empty tank with a gallon left in it!).  A bit like "44mpg Sir" isn't really 44mpg!!! 

[malcolmw]

Lexus say that the tank has a "Reference" capacity of 65 litres. I take this to mean that it is actually larger to take account of the factors which you mention. I should think that about 10% of the tank capacity as a reserve is reasonable and expected.

[Assa1974]

On my 400 the warning light comes on early into the final quarter and I;ve had the needle firmly on R for a few miles several times and it's taken less than 60 litres to fill so there's a healthy reserve. I reckon I can easily get 75 miles from the warning light coming on. It's very conservative.

[GSLV6]

That's good to know, especially when my average since picking the car up is only 32mpg!

[TRWeasle]

Thanks for this.  Methinks my 2012 3rd generation RX 450h has the same.  Although I also agree that it was done for a reason, and I won't be running her dry any time soon if I can help it!

[Lost it]

Really, you don't want to do this.

The fuel pump in most vehicles these days sits in the fuel tank. It uses the fuel in the tank to self lube and cool itself. That's the reason the light comes one with still a few litres in, to allow for the fuel sloshing around.

Even my Honda Motorcycle is the same. Says 22 litres, holds 24.

If the fuel is run that low regularly, there's a chance the pump might fail. I have no idea how hard it is to get to the fuel pump on a Lexus Hybrid? But is it worth getting those last few miles?