Premium Gas

[churp]

Originally Posted by jdium

Which brings me to my other point, don't smoke crack...

Most every gas was LEADED (no UN) before 1970. Leaded gas has a realative octane rating of todays "race' gas, like 110 or something...

Wrong, read WRBlues post.

Thanks WRBlue for correcting me....1970 was when the compression ratio dropped in the US....along with performance.

[eTiMaGo]

well.. I filled up today, just for experimentation's sake, with 95 RON ethanol mix fuel. It's actually a good bit cheaper than 91.

Although, my methodology will be flawed, as I immediately took a (relatively) long drive. In my normal driving, I will see one bar drop after about 50-55km, but this is after a few days of short trips, after this one long trip (almost 100km), the bar dropped at around 80km into the tank. I drove at a steady 110-130km/h the whole way, as I had a passenger I could not really rev her up and see how the higher octane may affect the high RPM characteristics... I'll report more once I have better information to share

[Yarii]

They're not telling you to run higher octane... They're just putting the RON in brackets because the entire world except north america uses RON to measure octane. In NA our pumps are labled with the average of the RON and MON measurements, which is generally 4 or 5 points lower. 87 octane gasoline in north american is 91 RON.

Originally Posted by churp

You must have a different owners manual, mine states:

SELECT OCTANE RATING 87 (RESEARCH OCTANE NUMBER 91) OR HIGHER.

This is page 178 in my owners manual. Obviously they know what a few of us are trying to pass on here!!!!!!!!!!!!!!!

The tests have been done before higher octane was ever put on the market (probably the 30's). The ECU has taken the "must have" higher octane in your car away....but it hasn't removed the fact that performance and milage will improve in most engines with it. Note that I am not saying it is cheaper to put the higher octane in....but where I live it's very feasable (Iowa and South Dakota 89 octane is the same price or cheaper than 87, and in Minnesota I get 89 for 2 cents more than 87) and I use 89 octane.

[Pavel Olavich]

Originally Posted by Moose

WOW. I just saw this.

Is this guy still here, or has he been banned?

1) ...did you every consider that you could fill your tank up with 87 octane and drive your same route 10 times and get ten different MPG results?

Yes, and they are usually within .3-.5 MPG each time. I actually do the math and keep a log. That's as close to scientific as we can get.

2) Your test lacks controls to be able to draw conclusions.

As does your opinion.

3) ....did you attend college?

Yes, Georgia Tech. I actually know the science- you think you know the science. And don't try any cute comebacks- I'll just look at my degree and my paycheck and giggle.

Will there be anything else Pavel? I generally reserve arguing on the internet for times when I have nothing more adult to do, but watching you unravel and make a fool of yourself is worth it.

Your testing methods belie your "Georgia Tech" education. Sorry, but it was sloppy....by the way, I'm sure your giggling paycheck would make me laugh off my ass too!

[Moose]

[Black Yaris]

Originally Posted by WRBlue

The rest of the world measures octane different than us in North America. In the EU and Australia, they advertise RON. Here we use an average of RON and MON. MON is a lower number than RON. YOU CAN'T COMPARE OCTANE RATINGS BETWEEN NORTH AMERICA AND THE REST OF THE WORLD.

The ignorance in this thread makes my head hurt.

Octane only measures the autoignition characteristics of gasoline. How easily it will explode without a spark.

THE ONLY THING THAT WILL CAUSE MPG TO INCREASE ARE O2 READINGS.

If the O2 sensor reads the car running rich, it'll lean it out within safe parameters. Lean = less fuel used = higher MPG.

HIGHER OCTANE DOES NOT CHANGE THE AIR-FUEL MIXTURE.

Higher octane gasoline can only prevent detonation. If your detonating with 87 octane, something is wrong with your engine/ECU.

A car runs a base timing and advances or retards it only within set parameters. And those parameters are ones set by Toyota Engineers as to be safe with low octane gasoline. The computer will not exceed those if you put high octane gas in and magically the computer knows.

Besides, there is no sensor that can tell what octane is used. To measure octane, you have to find out the percentage of volume is iso-octane and the percentage of volume is heptane. NO production car has the ability to do that...

And anyway, advancing timing does not cause less fuel to be used. It cause more power to be made from the fuel.

Everything else in this thread is anecdotal evidence. There are many, many, many variables. Elevation, wind, drag, tires, air pressure, surface type, load, weight, etc. The most important thing is repeatability. If you REALLY want to prove higher mileage, rent a couple weeks of dyno time in a lab. Control all the environmental variables to be constant for the whole week (temp, humidity, air flow, tire pressures). Empty the car 100% of all gasoline. put a predetermined mass of fuel in the car of a certain octane. Run about 40 tests and take the mean. IIRC 40 is the number where statistically each incremental test after that does not statistically significantly change the mean. Now change the octane and repeat all 40 tests.

Then and only then you can make assumptions if octane can change MPG.

so the higher octane combined with vvt-i will not change fuel econ?
I ALWAYS get better mpg with premium fuel than 87... the only peple that deny the fact are the ones that have not tried it

[Black Yaris]

Originally Posted by Moose

where did you find that picture of Pavel?

[Moose]

Originally Posted by Black Yaris

where did you find that picture of Pavel?

Same place I found this one...

[Black Yaris]

did you get ahold of his family photo's?

[cleong]

I'm not taking sides, just relating personal experience.

Over here we have four grades of fuel at the service station, 92, 95, 98 and 98 Premium.

Each indicates a RON (which I understand to be different from the US). 98 Premium reputedly is the most "powerful" due to additional chemicals that boost power as well as clean up the engine (note that it is still listed as 98 RON).

Of the four, the only fuel that I have not sampled is RON 92. The other three I have tried, and found that 98 generally provides slightly better mileage than 95, although the price difference does not justify the mileage gained. 98 Premium is supposed to "burn" faster, therefore its mileage is actually poorer than regular 98 fuel. However it does seem to feel the most powerful of the three, having more eager throttle response and the engine sounding smoother.

[WRBlue]

Originally Posted by Black Yaris

so the higher octane combined with vvt-i will not change fuel econ?

Yes. Why would it?

[cleong]

Originally Posted by WRBlue

Yes. Why would it?

Wouldn't a higher octane allow the engine to increase its timing and make more power, which means that less fuel is needed to maintain a given speed?

[Yarii]

Engine's don't detect the octane of fuel... They just retard the timing if they detect knocking. Without doing some ECU tuning, the timing will always be set to or below (if knocking is present) whatever toyota engineers pre-programmed it to be based on engine and air conditions.

Premium might help keep the timing from retarding under high engine load like heavy acceleration or towing/hill climbing when knocking might occur, but for most daily driving, the engine will use the same timing settings it uses on regular gas.

Originally Posted by cleong

Wouldn't a higher octane allow the engine to increase its timing and make more power, which means that less fuel is needed to maintain a given speed?

[cleong]

So we should only run the absolute minimum RON recommended and anything above is just a waste of money?

[churp]

No...it depends on how you drive. Lots of flat land and easy driving---87 octane. Lots of hills without slowing down and not creeping up them, and lots of fast starts----you may see a little better mileage with higher octane, but only during those higher load conditions. Each individual driver would have to judge for themselves if it would be a cost benefit....it's a slim one at best, but it may feel like a little more power in those conditions.

[eTiMaGo]

Originally Posted by cleong

So we should only run the absolute minimum RON recommended and anything above is just a waste of money?

that seems to be the consensus...

I've just looked through all the ECU and ignition related stuff in the repair and technical manuals... my head's spinning now, our humble little car has some pretty advanced systems...

I was trying to find out if the ECU has any kind of learning system, that might try to advance the ignition timing until knock is detected, as this would allow it to run the maximum ignition advance regardless of the fuel used. But I find no evidence of this, but also no evidence of the contrary. From what I gather, the actual spark timing is determined by the crankshaft and camshaft position sensors, and retarded by the knock sensor when required.

What I did find out, though, is that the spark advance can be set in a range from -64 to +63.5 degrees, and the normal value when idling should be between 0 to 14 degrees.

Truthfully, the only way we can know for sure, is to have some device such as the Toyota intelligent tester used by the technicians, to monitor the actual ignition timing while driving with different tanks of fuel, such as 87, 91, 95 octane, and compare the average timing between each tank. Until then, it's really a matter of educated guesswork and subjectivity...

[WRBlue]

Originally Posted by churp

No...it depends on how you drive. Lots of flat land and easy driving---87 octane. Lots of hills without slowing down and not creeping up them, and lots of fast starts----you may see a little better mileage with higher octane, but only during those higher load conditions.

And only if your getting knock during thoes times. We drove up to Tahoe a couple months ago in the Yaris. It was slow, we did climb 8000 feet, but there was no knock and we got about 35MPG (higher than our average). Next time we're taking the WRX though ;)

[churp]

Originally Posted by WRBlue

And only if your getting knock during thoes times. We drove up to Tahoe a couple months ago in the Yaris. It was slow, we did climb 8000 feet, but there was no knock and we got about 35MPG (higher than our average). Next time we're taking the WRX though ;)

You will not get a knock unless the ECU malfunctions....but it is guaranteed a 10.5 to 1 compression engine without knock sensors and ECU runs like crap on 87 octane. You would be able to get it to run level ground and very mild acceleration with good mileage,but you wouldn't want to drive up a hill. If you retarded the timing enough to be able to climb a hill the gas mileage would suffer big time. The ECU w/ knock sensors are wonderful items!! Premium would only add a little more power/efficiency on the climb IMO...definitely not enough to match the WRX!