Premium Gas

[Moose]

Originally Posted by cali yaris

{ OFF TOPIC }
As far as I know, sex was invented in 1976.

Don't taunt the married animals.

Sorry, I just don't like mean people- usually mean and idiot go hand in hand, so it's that much more maddening.

I'm done, I promise.

Back on topic.

[Kaotic Lazagna]

wow, my thread is going to start a war all over again.

[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

[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.

[cleong]

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

[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...

[fu_im_from_texas]

Originally Posted by eTiMaGo

... our humble little car has some pretty advanced systems...

+1

You dont get to design dynamic system controls at toyota without being very sharp. Toyota recommends 87 ...

[churp]

Originally Posted by fu_im_from_texas

+1

You dont get to design dynamic system controls at toyota without being very sharp. Toyota recommends 87 ...

Toyota doesn't recommend 87.....they say: Select Octane Rating 87 or higher (read the owners manual, page 178, or other posts)...in the English language this means 87 is the lowest they allow. And yes they are very sharp.

[fu_im_from_texas]

Originally Posted by churp

Toyota doesn't recommend 87.....they say: Select Octane Rating 87 or higher (read the owners manual, page 178, or other posts)...in the English language this means 87 is the lowest they allow. And yes they are very sharp.

churp,
you are right. the "or higher" means that we should all run 110 octane race fuel ... i bet you will get 87 mpg and 200 hp ... your "understanding" of the english language is revolutionizing the yaris...

[hystria]

Originally Posted by cleong

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

PROBABLY higher octane/RON will provide better fuel economy with this car... but the difference will be too minimal to be easily measured by just checking a mileage variation. YES, Toyota recommends using higher octane/RON for this engine in order to obtain better mixture burning, resulting in less polluting emanations. Buying 10-15% more expensive 89/91/94 gasoline won't result in 10-15% mileage increasing. Check out the black smut (?) on the exhaust when running on 87 octane, then whip it off and switch to 91 and check again.

[fu_im_from_texas]

Originally Posted by hystria

PROBABLY higher octane/RON will provide better fuel economy with this car... but the difference will be too minimal to be easily measured by just checking a mileage variation. YES, Toyota recommends using higher octane/RON for this engine in order to obtain better mixture burning, resulting in less polluting emanations. Buying 10-15% more expensive 89/91/94 gasoline won't result in 10-15% mileage increasing. Check out the black smut (?) on the exhaust when running on 87 octane, then whip it off and switch to 91 and check again.

"....using a higher octane gasoline than your owner's manual recommends offers absolutely no benefit. It won't make your car perform better, go faster, get better mileage or run cleaner. Your best bet: listen to your owner's manual."
http://www.ftc.gov/bcp/conline/pubs/autos/octane.shtm

why do people insist on ignoring empirical and statistical data?

[bearda]

This is one of those discussions that just doesn't go away. I've seen the same thing on almost every non-premium fuel car forum I've seen. The signal to noise ratio tends to vary, but you've always got a couple people clinging to numbers and reports, a couple people clinging to their anecdotal evidence, and a couple people clinging to some hope that they can improve performance.

Just to add fuel to the fire, though, I don't think higher octane gas is going to do much of anything for you (nothing good, at least). Higher octane gas doesn't give you higher performance; it just resists pre-detonation. If you're at the point where the ECU is retarding timing due to pinging it'll keep you from losing performance. Unless the ECU is really designed for performance it isn't going to keep advancing the timing on it's own unless it's already retarded the timing (There are some that do do this. The WRX actually starts with a very conservative timing advance then ramps it up until it knocks, then pulls it back a little).

Higher octane gas CAN give you better mileage if the car can take advantage of it. Octane rating is basically a measurement of how long it takes fuel to burn. If the fuel burns longer you don't need to burn quite as much of it in the optimal case. You've got to get the ECU to realize that, though. If the ECU keeps the same ignition timing/AFR/whatever you're not going to see any benefit.

One thing I have seen with higher-octane fuel on a car factory-tuned for 87 is starting delay. From what I can tell (and this is coming almost entirely out of my ass, as this goes right past my league) since higher octane gas is more resistant to predetonation sometimes it's also a little too resistant to initial detonation. You try to start the car and the ECU finds the gas a little harder to light than it thought. Not a big deal at all, but at times an indicator that lower octane gas can actually run better than high-octane.

If you're looking for the best gas for your car just buy GOOD gas, not higher-octane gas. Go with a station that stocks gas with additives and detergents in it's 87. Chevron is a great example of this; they put their Techron additive in all the gas they sell. Once again, it's isn't going to add any more performance or gas mileage the car didn't have at one point. Maybe it'll keep it running a little cleaner, though, and it's my personal opinion that you're more likely to see a benefit from that than running high-octane gas.

[hystria]

Originally Posted by fu_im_from_texas

"....using a higher octane gasoline than your owner's manual recommends offers absolutely no benefit.

TRUE. As per Yaris manual, it recommends 87 or higher. Why "or higher" ? Ever wonder why Toyota recommends wasting your money ? With NO REASON ? Is Toyota in business with Shell ? Well, if not, there should be a reason, unless there are places on Earth that sell only 89 or higher octane gasoline... don't think so...

Engines are optimized to run with a precise level of octane. If an engine requires 87 and the owner put 89 or higher, there will be absolutely no benefit for the engine. On the other hand, if and engine is optimized to run with 89 and the owner uses 87, the engine will not run at 100% performance. It will knock more or little because the mixture ignites before the optimum moment during compression, thus leading to hot points on the piston/ring surface. Because the mixture ignites before the moment when the engine compression is optimal, it produces less overall performance. But not by much, one will not be able to feel any difference.

To resume... if using 87 the engine starts knocking, try changing the brand... the Yaris engine should not be knocking to an audible/damageable level while using good quality 87 octane gasoline.

[Pavel Olavich]

Originally Posted by hystria

TRUE. As per Yaris manual, it recommends 87 or higher. Why "or higher" ? Ever wonder why Toyota recommends wasting your money ? With NO REASON ? Is Toyota in business with Shell ? Well, if not, there should be a reason, unless there are places on Earth that sell only 89 or higher octane gasoline... don't think so...

Engines are optimized to run with a precise level of octane. If an engine requires 87 and the owner put 89 or higher, there will be absolutely no benefit for the engine. On the other hand, if and engine is optimized to run with 89 and the owner uses 87, the engine will not run at 100% performance. It will knock more or little because the mixture ignites before the optimum moment during compression, thus leading to hot points on the piston/ring surface. Because the mixture ignites before the moment when the engine compression is optimal, it produces less overall performance. But not by much, one will not be able to feel any difference.

To resume... if using 87 the engine starts knocking, try changing the brand... the Yaris engine should not be knocking to an audible/damageable level while using good quality 87 octane gasoline.

The "or higher" phrase only means that if 87 is not available, then using a higher octane is not going to damage your engine.

Don't be so quick to read more into the words, then what is literally meant.

Also, to suggest as a remedy, to use higher octane than called for in the manual, a way to remove knocking is plain wrong. It would be far better to take the car in and determine why it is knocking at the required octane, and to remedy the problem. Going up in octane is a band-aide that only masks a real problem.

[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.

[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!