Gas tank capacity??
09-28-23, 05:29 PM
#46
Racer
Government fails once again. The brainiacs /s at fueleconomy.gov just took their 22mpg "combined" mileage and multiplied it by the RX's 19.2 gal fuel tank capacity. 22 x 19.2 = 422.4. That number assumes you run the tank bone dry. Given that the tank includes a low pressure fuel pump that depends on fuel for lubrication, it also means you'll be replacing that pump very often if you try to duplicate the government's numbers.
My practical reality is that I get 280-330 miles on a tank. I do a little better occasionally with lots of highway miles on flat terrain. (My RX is not an F Sport, but the F Sport package does not materially affect mileage or range.) It does appear that the Range figure after a fill-up is based on the mileage from the last tank. At least that's my anecdotal experience. BTW, I've run my RX down to zero miles remaining on the Range display, and never put more than ~16 gallons in the tank. Lexus tries to protect drivers from themselves, at least with respect to low fuel problems.
My practical reality is that I get 280-330 miles on a tank. I do a little better occasionally with lots of highway miles on flat terrain. (My RX is not an F Sport, but the F Sport package does not materially affect mileage or range.) It does appear that the Range figure after a fill-up is based on the mileage from the last tank. At least that's my anecdotal experience. BTW, I've run my RX down to zero miles remaining on the Range display, and never put more than ~16 gallons in the tank. Lexus tries to protect drivers from themselves, at least with respect to low fuel problems.
09-28-23, 05:41 PM
#47
The computer uses a best guess at your expected mpg based on medium term driving habits, I don't have any exact formulas but I don't feel this exactly mean last tank, as you could fill up every 3gallons and count as a refuel; and I don't think it uses the user's ave MPG tracker feature either.
It will auto adjust range as it goes changing both the expected MPG and multiplying by estimated fuel left in your tank. It is not static for a whole tank.
If you scroll through, you can find screens that display instantaneous MPG going all over the place. A modern fuel injected vehicle knows exact fuel rates so it knows MPG and can estimate tank volumes. It is not hard for it to do some rolling calculations as it goes. It won't jump the Range up and down though to help the humans stay sane.. It'll only go 1way and instead pause the range countdown until it catches up and can continue the countdown.
It will auto adjust range as it goes changing both the expected MPG and multiplying by estimated fuel left in your tank. It is not static for a whole tank.
If you scroll through, you can find screens that display instantaneous MPG going all over the place. A modern fuel injected vehicle knows exact fuel rates so it knows MPG and can estimate tank volumes. It is not hard for it to do some rolling calculations as it goes. It won't jump the Range up and down though to help the humans stay sane.. It'll only go 1way and instead pause the range countdown until it catches up and can continue the countdown.
Last edited by raytseng; 09-28-23 at 06:02 PM.
09-29-23, 05:59 AM
#48
The computer uses a best guess at your expected mpg based on medium term driving habits, I don't have any exact formulas but I don't feel this exactly mean last tank, as you could fill up every 3gallons and count as a refuel; and I don't think it uses the user's ave MPG tracker feature either.
It will auto adjust range as it goes changing both the expected MPG and multiplying by estimated fuel left in your tank. It is not static for a whole tank.
If you scroll through, you can find screens that display instantaneous MPG going all over the place. A modern fuel injected vehicle knows exact fuel rates so it knows MPG and can estimate tank volumes. It is not hard for it to do some rolling calculations as it goes. It won't jump the Range up and down though to help the humans stay sane.. It'll only go 1way and instead pause the range countdown until it catches up and can continue the countdown.
It will auto adjust range as it goes changing both the expected MPG and multiplying by estimated fuel left in your tank. It is not static for a whole tank.
If you scroll through, you can find screens that display instantaneous MPG going all over the place. A modern fuel injected vehicle knows exact fuel rates so it knows MPG and can estimate tank volumes. It is not hard for it to do some rolling calculations as it goes. It won't jump the Range up and down though to help the humans stay sane.. It'll only go 1way and instead pause the range countdown until it catches up and can continue the countdown.
09-29-23, 12:40 PM
#50
I assume the OP is aware the humans low fuel light and computer est. range and is set with a 2.9gallon reserve?
There are other threads that explain the common reason is because low fuel will damage the fuel pump. I think this is only half the story.
Obviously gasoline is a liquid, so it sloshes around. Unless you have the vehicle on a treadmill, when you get to low fuel the real issue is the fuel can't be picked up reliability. If you are on a slope you might not get fuel at all, so they can't guarantee the vehicle will run. So this point is more about reliable fuel delivery due to gravity and liquids than just overheating the pump.
Additionally the problems are more than just the pump overheating. If it is barely picking up fuel, you could get unreliable fuel delivery to the engine. You can get misfires and surges. This is just as much of a concern. It is like for your home electrical where a brownout with power flickering is worse and cause more damage than if the grid shut down gracefully.
Anyway, if it's the zombie apocalypse, and you must drive the car until it dies, you probably could go that extra 2.9gallons x mpg assuming you're on a nice flat road.
There are other threads that explain the common reason is because low fuel will damage the fuel pump. I think this is only half the story.
Obviously gasoline is a liquid, so it sloshes around. Unless you have the vehicle on a treadmill, when you get to low fuel the real issue is the fuel can't be picked up reliability. If you are on a slope you might not get fuel at all, so they can't guarantee the vehicle will run. So this point is more about reliable fuel delivery due to gravity and liquids than just overheating the pump.
Additionally the problems are more than just the pump overheating. If it is barely picking up fuel, you could get unreliable fuel delivery to the engine. You can get misfires and surges. This is just as much of a concern. It is like for your home electrical where a brownout with power flickering is worse and cause more damage than if the grid shut down gracefully.
Anyway, if it's the zombie apocalypse, and you must drive the car until it dies, you probably could go that extra 2.9gallons x mpg assuming you're on a nice flat road.
Last edited by raytseng; 09-29-23 at 01:25 PM.
09-29-23, 02:31 PM
#51
On a round trip Dayton > Indianapolis > Dayton (266 miles) on Tuesday of this week, plus ~50 miles of local short-trip driving, my F-Sport got 24.8 mpg, per gas pump refill calculation. I use the radar cruise control as much as possible -- that seems to boost efficiency, for some reason.
09-30-23, 07:26 AM
#52
On a round trip Dayton > Indianapolis > Dayton (266 miles) on Tuesday of this week, plus ~50 miles of local short-trip driving, my F-Sport got 24.8 mpg, per gas pump refill calculation. I use the radar cruise control as much as possible -- that seems to boost efficiency, for some reason.
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