Only 500 miles, but good mileage so far

Thats great! Youre gonna love this car, i find new reasons to love it every day!

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congrats and welcome! thats excellent work, all the best.

 

If you're inclined: start tracking mpg: record your fillups and distance travelled, keep a log.

 

Toyota fudges the numbers, 5~10% positive bias. It's at least semi consistent bias, but something to keep in mind. Also, whenever you disconnect the battery, the trip data is gone. Really depends how much you care, if you're seriously into tracking tank by tank, or just want a bit of feedback.

 

Yeah - I calculate my fuel economy at every fill-up based on actual litres pumped, and I also compare it to the reported "Trip B" fuel economy, which I reset at each fill-up. The figure reported by "Trip B" is always about 5 to 7% optimistic - i.e., it reports slightly better fuel economy than I actually get as measured by litres pumped. And I seen this reported by a lot of people, so it seems to be pretty consistent across the fleet.

 

After a few accidental resets of trip meters, I opted to recording odometer reading at each fill up, then do the math: subtract previous from current odo reading, to get distance travelled. With a spreadsheet it's very easy, and fuelly can be setup that way as well. I still reset trip meters, for feedback and as a cross-check.

Our previous Honda Civic Hybrid had a fuel economy display that was either spot-on, or slightly pessimistic. It can be done. It's a bit embarrassing, that the auto maker leading the mpg pack insists on exaggeration.

 

The only plausible answer, sadly, seems to be: by design. The errors are quite consistant.

 

G'day,

Checking my speedo against a necessarily accurate GPS system's indicated velocity, my c is 4-5% fast. Better than my wife's Yaris at 9% fast, but not as good as my traded-in Echo at 0-1%. These variances were also consistent with the do-it-yourself roadside speed indicator signs - 6 signs spaced 1km apart along the road so you could check your speed/odometer.

Does everyone correct for their likely odometer error when measuring fuel consumptions? Or at least, mention when they do do such a correction? Otherwise, car-to-car fuel use comparisons are questionable, at the decimal place values at least.

Presumably the Prius uses its own distance measurement (reported to us as ODO/TripA/TripB), so doing a manual calculation based on your fuel from the pump per your odometer reading should match the car's internal calculation - any difference being in the fuel volume value used in the calculation.

Thus far (I've had the c for 3 months), I see a fairly consistent over estimate of about 5% by the car compared to my L/100km value, using the same ODO readings. Litres in topping up for the distance since last topping up. I believe our local government reliably checks the accuracy of service station pumps so the fuel volume estimate by the car itself seems more suspicious of being 'optimistic' (reading less than it should).

So, there is a variance in the the fuel volume and in the distance travelled for that volume, both tending to exaggerate the efficiency of a vehicle getting from A to B. The distance, A to B, is presently like Caesar's wife .

David S.

 

There is no connection between speedometer and odometer accuracy. The first typically reads high, by legislation, to slow people down. The second has to be reasonably accurate, or lawyers get interested.

And mpg accuracy? Now who would want to fudge that...

 

My speedometer seems to be very accurate, but measured manually and against my GPS. I never see more than about a 1km/h difference, and I attribute that to rounding error.

But I don't think I've actually checked the odometer. I'll have to do that one day.

 

My speedometer seems invariably higher compared to my Garmin GPS, around 2%. I'm ok with that, abide by what the speedo says. The odometer is going to be reasonably accurate though, at least with stock tires. If it's reading high, for example: lawyers will be going after the manufacturers, with claims that cars are running out of warranty prematurely.

 

I purchased this little gem on Saturday and I can't even believe how quiet it is. I had no idea that you could enjoy something you can't even hear and still gets me 55mpg on the Freeway & 65 in town. Don't know if its the 91 Prem. octane I'm putting in it. Either way I'm excited to have became a Jedi Prius Driver!!!

 

Premium is higher octane, it's sole purpose being to prevent pre-ignition in high compression engines. It's a small percentage, the cars on the road that actually need the stuff. But you wouldn't think that, looking at the pump arrangements in gas stations. Anyway: it'd be spec'd in the Owner's Manual if needed. Waste of money.

 

G'day,

Here in NSW, we have the option of E10 - up to 10%vol ethanol in regular unleaded.
Regular here has a RON of 91 (Research Octane Number - 'octane' (2,2,4-trimethylpentane) is RON 100 for the rating test purposes) but E10 goes up to RON 94 with the alcohol addition. Alcohol has a high RON, in other words.

However, E10's 'power' (combustion energy or calorific value) is decreased since there is more energy in burning the pure hydrocarbon 'regular' compared to burning the alcohol mix (ethanol has a lower calorific value). If burnt with full or equal efficiency, of course.

In theory, with its lower calorific value, 94RON E10 should give slightly less milage than 91RON regular, but it's more how and where and when the car is driven, than the fuel itself, that determines mpg or L/100km. I see no difference between regular and E10 for my driving experience.

Our "Premiums" in Oz have 95 or more RON and, as Mendel Leisk rightly said, are only needed in high compression engines where power, not efficiency, is the target. European cars seem to think this high compression is a good idea with their tendency for turbo-boosted small-capacity engines. Hence their need for high RON fuels.

The designed minimum RON for the Toyota engine's fuel is 87, merely to stop pre-ignition ('knocking' or 'pinging' where the fuel-air mixture ignites prematurely due to the compression in the cylinder before the spark plug sparks at the intended part of the stroke).
Japanese cars (engines) seem to take a more practical, world-friendly view where across the world, fuels may be "variable" so the lower RON the car can use, the better.

When it's available, I use E10 in my c. E10 is taxed a little less here than Regular (about 3 cents per Litre less).
But by choice, I would never use our over-priced 'Premiums' (these can be more than 15 cents per Litre dearer!). These 'Premiums' (definitely a marketing term, not a technical term, in my opinion) have pretty much the same power (combustion energy) as the other fuels on sale, and are wasted in a well-designed low-RON ICE such as the Prius's.

Then again, it's hard to argue against the 'placebo effect' . If you think it'd do you or your car good, 'go for it' . It's only money after all .

Keep smiling,

David S.