Real World MPG Numbers

I find that the higher octane/priced fuel feels less rough and less noisy when you ram the prius engine up a hill. On normal roads, there isn't much of a difference in terms of feel. But at 14% higher cost, the 12% better mpg might or might not be worthwhile?

Esso Supreme vs Esso Extra

 

I really doubt going up an octane grade is going to gain you any mpg improvement, let alone 12%. That'd be all over the news, lol.

 

You are NOT getting 12% better mileage on premium fuel. Any difference you are seeing is due to other factors. This has been tested and retested by SAE and others.

 

I'm not sure what SAE papers tested on what kind of car. But this is how I tested on my prius gen 4 and got my real world(basing on prius computer) mpg numbers in two separate days:

1)Ran fuel tank til near empty.(fuel light up)
2)Fuel up full tank at the same gas station(Reset the trip odometer) that is located just before the highway(20km) back to my home at around 5am(zero traffic). . Both temperature and weather was consistent on both days.
3)Drove back to my home at the same cruise control setting speed of 80km/h.
4) That's how I got to 4.1l/100km(57mpg) for Esso Extra and 3.6l/100km(65mpg) for Esso Supreme.

 

Just for reference:



(From Esso Canada site)

What about Esso Regular?

Barring other variations, say traffic congestion or whatever, I'd grudgingly say you're being methodical in your testing. Still, I'm very sceptical, for a couple of reasons:

1. Higher octane fuel's reason for existence is to prevent pinging in the smattering of higher compression engines on the road.

2. A 12% increase in fuel economy, and no one's heard about it?

One variable maybe being overlooked: percent of ethanol added to the different grades.

 

I've got almost 12k miles on my '16 eco. lifetime average is 57.6 mpg. Thats mostly 72mph highway as well.

 

You don't have enough data points to draw a conclusion. You would need to drive a measured course with several repetitions for each type of gas. You would also have to account for ambient temperature, pressure and temperature of the tires, wind speed, starting state of charge of the traction battery and a myriad of other variables to be sure that you were seeing a real difference and that difference was due to the gasoline choice.

Of course, this is why the testing is usually done on a dynamometer in controlled conditions such as indoors.

What you have done barely rises to the level of anecdotal evidence.

 

Great point about the ethanol and other octane boosters.

 

Here are SAE papers that show increased octane doesn't help MPG and may have a negative effect: The Impact of Gasoline Octane on Fuel Economy in Modern Vehicles Effects of Fuel Octane Rating and Ethanol Content on Knock, Fuel Economy, and CO2 for a Turbocharged DI Engine

There is some talk that using higher octane could allow engineering compromises to improve mileage. But, not with the current fleet of cars that are optimized to 87 octane.

 

3rd fillup.Colder weather taking it's toll...

539 miles with 9.65 gallons

60.5 on the MFD 55.9 calculated

 

Still bothers me that the MFD is 7.5% higher than manual calculations...

 

I am lazy. I just use the MFD as an indicator and have not bothered to compute manually.

 

Looks like some are really close, and others (like you and me) are off quite a bit... I've been reading backwards on this thread looking for trends, but haven't found any reasoning on the delta.

Just curious... I'm quite happy with matching the EPA combined mileage in freezing winter weather. It'll be interesting to see what late January / early February does to the numbers...

 

OMG! I'm glad that I really don't care. Like prodigy, I just use the car indicator. Perhaps the discrepancy derived from the fact that cars speedometers are designed to overread the actual mph.

 

I got a 4% initially, and since then it has been 4 or 5%, but today when I filled up the discrepancy was 10%. Wondering if the cold weather and snow has something to do with it, or if it was just this particular fill up and pump

 

Had the car for just over 2000 miles and I'm happy with the MPG as I'm seeing it increase on each tank fill. Just got 64mpg (53mpg US) on a 300 mile round trip at 3c (37.4f) and an average speed of just over 50mph. Road mix was 60% Motorway 40% normal roads. At this time of year that's 9mpg (7.5Mpg US) more than what my Hybrid Yaris would do on the same trip. Can't wait to see what it will do in the summer, based on this comparison hopefully I'll get over 75mpg (62mpg US)

The above figures are all based on in car readings.

 

What temps? Amazing you guys get the Hybrid Yaris ... :O The US gets screwed out of so many options, and in 2017 we will be even more screwed (possibly)...

 

The temp for the 300 mile trip was 3 degrees C, when in the Yaris it was the same time of year and the temp was similar. The best mpg I got from the Yaris was 66mpg (54mpg US) when it was above 15 degrees C.

 

Do you guys have the Prius C model? the MPG sounds like it, maybe the Yaris Hybrid in Europe = Prius C here?