Reserve Tank

I do not think it is a separate tank, but yes, due to the potential damage if you ever run out of gas, there is about 2 gallons left when it shows empty.

Do your best to never use it.

 

a reserve tank?

 

2 gallons of reserve in the tank.

SCH-I535

 

no. you can go farther, but i wouldn't push it, it's there for safety, in case you're not near a gas station.

 

As Jimbo said, the reserve is not in a separate tank, but is in the main tank below the point the gauges show empty.

This gauge 'error' is not unique to the Prius, but is the norm across the auto industry. If the manufacturers didn't intentionally do this, the combination of cheap inaccurate components, highly variable and unpredictable fuel consumption, and poor driver attention and planning, would cause far more drivers to run out of gas. And they would blame the car makers on the many occasions when the gauge earlier displayed enough fuel before MPG conditions deteriorated. So the gauges have enough built-in warning that when drivers find themselves stranded, they cannot rationally claim lack of warning.

For a better feel of how much range you probably have left, read the first post of this long thread: [WARNING] Running out of gas (Gen III).

 

well, it takes a little bit of math. fill the tank, and divide the miles driven by the gallons. for example, 480 miles divided by 9.5 gallons equals approximately 50 mpg. you can use a calculator in this class.

 

Miles remaining, fuel reserve, etc., are irrelevant when trying to get an accurate idea of MPG. These are just warning to the driver to help prevent running out of fuel.

Just keep a fuel log, showing your Trip B miles between refills, and the amount of fuel added when refilling. MPG = (Trip B miles ) / (gallons pumped in). That is all you really need.

If you are horrible with math, than playing brinksmanship with an emptying fuel tank is going to leave you stranded by miscalculations and the inherent uncertainty in knowing how much gas is actually available, and how much is being burned as conditions vary. MPG is almost never a fixed number, it varies widely even during a single trip.

 

no, it really is a 11.9 gallon tank. how much of it you use doesn't affect mpg, just range. all cars are like this, is this your first?

 

Register with Fuelly.com and when you fill up your tank, just record the odometer miles, gallons filled, and price per gallon (get a receipt). Then enter your odometer reading in fuelly.com, it will calculate your mpg for you.

SCH-I535

 

it's funny what you don't notice about a car when you aren't paying attention to mpg's.

 

Forget about all the car's meters. Record your odometer reading when you fill up. Drive 'till tank is lowish. Fill up, and note new odometer reading. Subtract old odo reading from new. That's your distance travelled. Divide that number by the gallons you put in. That's your mpg.

 

Fuel consumption or fuel economy doesn't have anything to do with size of the tank or how much fuel is in it when you fill up. In the US, we measure it as miles per gallon. (In the rest of the world, it's liters per 100 km, which is the inverse of mpg, in the "math is confusing" realm, so let's not talk about that now.) If you drive 500 miles and fill up with 10 gallons, you've got 50 mpg. If you decide for whatever reason to fill up after 250 miles, you're going to fill up the tank with something like 5 gallons, so still 50 mpg. If you decide to fill up after driving only 100 miles since your last fill up, you're only going to get 2 gallons in that tank.

What really messes up your numbers is not filling the tank. I'm sure I'm not the only one who remembers being cash strapped during the gas crisis of the 70s and only buying $2 worth of gas. Don't do that. If you fill up the tank every time, each calculation of miles driven since the last fill up divided by gallons pumped today will give you an accurate mpg. Of course, that mpg is going to vary, but not a lot. Oh yeah, and don't run the tank dry. It's got nothing to do with fuel economy, it's just a bad idea.