What is your number of "miles to refill" upon fill up? Tips for calculating actual MPG?

• true_fuel_gallons = tripmeter_miles / tripmeter_MPG
• true_MPG = true_fuel_gallons / true_miles
  • true_miles = calibration_constant * indicated_miles

The calibration constant is measured by using either highway mile marker or GPS distance measurements against the tripmeter_miles.

Bob Wilson

 

IF the Prius is refilled tank about the same time when the fuel gauge's last bar flashes (and gives you a beep) AND the refueling gas pump is allowed to shut off automatically at the first click ( never overfilling the gas tank) THEN if the Prius is sitting on a flat surface each time the fuel tank level is measured then the internal sensors for the Prius gas tank should be accurately measure the fuel inside the gas tank to 0.10 of a gallon consistently. The Prius fuel tank might officially hold 11.9 gallons but the Prius gasolone tank internal sensors only read up to 11.4 gallon and do not read below 0.7 gallons. The first click at the gasoline pump will prevent you from going beyond 11.4 gallons and the first warning beep and first time that the last bar on the fuel gauge starts blinking prevents you from going below 1.9 gallons in your fuel tank.

 

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My hunch is the mpg the car tells you is higher than calculate mpg, because Toyota set it to be that way. Cheap advertising, make owners feel good, whatever. I've kept a running tally of all but the first couple of 1000 kilometers, am at 44000 km's now, and the average error between calculated and Toyota's claimed is 8%.

Tips for calculating mileage:

1. Use odometer readings, just use the trip meter for back up, it can be accidentally reset.

2. every time you gas up, record the odometer. Subtract the previous from current, that's your travelled distance between fill ups. Then divide the distance by the gallons you needed to refill.

3. Don't sweat getting the same gas level, by filling to the neck or whatever. Just fill till it shuts off. Any minor variations will cancel out with the next fill up.

4. Forget about "miles to refill". Just refill when it's convenient, whenever it's getting kinda low. Don't push it too far.

 

Read my #3, lol. You're overthinking it. Even a single tankful calculation will be reasonably accurate, without any special considerations regarding tank size, hidden pockets, etcetera. And any discrepancies cancel out on the subsequent tank calculation.

 

It wasn't until I replaced the OEM tires that I finally figured out what was going on. The original tires are 'undersized', the revolutions per mile. This gives the false indication of better mileage than true in part because the car is using 'indicated', not 'true' miles.

Bob Wilson

 

The "miles to refuel" makes me think of the "ETA" on any GPS. It's accuracy depends on if you stay consistent. The GPS calculates your current speed, and it may even know the listed speed limits on the programmed route, but it can't account for what changes. The closer to your destination, the more accurate it gets.

I've been getting 525-550 tanks, and I've consistently found that one Pip = 50 miles to the Prius' "mind." That last Pip is 50 miles and it blinks (with warning) when it hits 25 miles. Checking my math, the 1 Pip = 50 miles is fairly spot on (for me). Of course, I'm sure it adjusts based on "free" miles you might get based on running electric only (or near to no gas), but I'm guessing it only recalculates how many miles you have left based on gas consumption and NOT your actual traveling. This means if you're getting 99+ mpg going downhill on an interstate, it might keep reading 56 miles to fuel up until it senses X amount of fuel consumption no mater how far you've actually gone at 99+ mpg.

 

Somewhat of a newbie to all of this. I traded in a Jeep Grand Cherokee. For a nicely equipped 2010 Certified Prius 3. Have put on about 7,500 miles since I bought it

I am currently averaging 46MPG. While this is a huge improvement on the 16 MPG I got on the Jeep I can't seem to get it any higher

I do mostly city driving and would classify my driving style as aggressive. But I have tried on several occasions to drive lightly and see no difference

Suggestions,thoughts would be appreciated


iPhone ?

 

If you bought your Prius used or just want to reset the miles to empty after learning pulse and gliding, etc., pull and reset the fuse to the MFD (or disconnect and reconnect the 12V battery). This will default the miles to empty to 600 and it'll adjust over time based on your driving.

Warning: You'll lose your trip A/B info as well.