Just filled up the tank with 91 octane premium fuel

[The Spectacle]

I'm digging this up from the dead rather than creating my own thread because I'm sure it would just spiral down the same road.

I've just filled up my tank with 89 after 3 years of nothing but the 87 and there is DEFINITELY a difference in throttle response and midrange power. I'm still a bit shocked myself but its there.

I read through a few of these responses and its clear that not many of you know how knock sensors and timing retard/advance work. That's all well and good but I just want to state for the record that Yaris behaves slightly different if you put higher octane in it.

[Flipper_1938]

Originally Posted by borezack

Hello first post here.

I have an 08 sedan.

Just would like to know if I should change from using 85 to 87.

I'm driving at 3000 to 10000 ft elevation and regular here is 85, plus is 87 and premium 91.

Also Just took a trip and was about 200ft above sea level and I used 87 since that was regular and my car felt like a rocket ship lol

Just would like some input.

Thanks

Probably had more to do with the denser air than the fuel...

[ROCKLAND TOYOTA]

Originally Posted by The Spectacle

I'm digging this up from the dead rather than creating my own thread because I'm sure it would just spiral down the same road.

I've just filled up my tank with 89 after 3 years of nothing but the 87 and there is DEFINITELY a difference in throttle response and midrange power. I'm still a bit shocked myself but its there.

I read through a few of this responses and its clear that not many of you know how knock sensors and timing retard/advance work. That's all well and good but I just want to state for the record that Yaris behaves slightly different if you put higher octane in it.

im SHOCKED it took you 3 years to fill up with something else!!!

WELCOME to the club and when you get to the last few bars on the guage you'll notice they don't disappear as fast.....

[The Spectacle]

Yaris is my daily driver and my other car is 400whp+ so I have never really bothered. But curiosity got the best of me so I gave it a shot

[Flipper_1938]

For shits and giggles, I filled up with a tank of premium.

....and I did get better mileage.

My normal in mixed driving is 40 mpg. On this tank, I got 43 mpg!

But with the added cost of premium ($.20 per gallon/ $2.00 per tank), it is pretty much a wash.

I am going to see what happens with 89 octane (mid grade) on the next fill up.

[A-Dingo-Ate-My-Baby]

Originally Posted by The Spectacle

I'm digging this up from the dead rather than creating my own thread because I'm sure it would just spiral down the same road.

I've just filled up my tank with 89 after 3 years of nothing but the 87 and there is DEFINITELY a difference in throttle response and midrange power. I'm still a bit shocked myself but its there.

I read through a few of these responses and its clear that not many of you know how knock sensors and timing retard/advance work. That's all well and good but I just want to state for the record that Yaris behaves slightly different if you put higher octane in it.

this may be because 3 years of carbon buildup on the pistons incrementally increases compression, therefore if you are having the knock sensor retard timing...higher octane will reduce that somewhat... which translates into smoother power. 3 years of buildup is just a thin layer but will increase compression [and small carbon chunks also create points for detonation to occur]. minor overall effect but that could be the reason for smoothness. still won't go any further down the road with higher octane, but I bet it can smooth the power delivery. if you wind on the yaris all the time there will be less carbon, or if you seafoam it, or use bg44k, that sometimes makes carbon chunks flake off and they get burned up at the cat...but by far the best thing is pull the head and use direct solvent or steam on the pistons, that removes carbon. [of course you are looking at a lot of work for an incredibly minor issue.]

[The Spectacle]

I disagree. I don't think it has anything to do with carbon buildup...takes 100k+ for that to be any type of issue. I might have 40k on the car.

I attribute the change due to a very sensitive knock sensor and some very conservative timing maps from Toyota for 87 octane. I'm averaging about the same MPG, as on 87...but I the car drives so much better that don't really care.

[comk4ver]

I'm going to revive this old post as well. I started noticing a shake during idle with my foot on the brake. When I took it to the mechanic at 70,000 miles he said, it weird that you're complaining about a shake in the car since your spark plugs are good for 100,000 but I changed them. What gas do you use, I told him BP the lowest one. He said that recommends Chevron and to use the high end stuff. So I did, but that was like three years ago? I looked at the manual today while the car was refueling and noticed that the manual says 87 or better.

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[comk4ver]

About three years ago my car was shaking at stop lights with my foot on the brake. When I took it to the mechanic, he looked at it and said if it did again to come back and change the spark plugs. When it did it again, he said that I was crazy because the spark plugs were manufactured to last up to 100,000 he changed them out at 70,000. He also asked me about what gas I used I told him BP 87. He told me to switch to Chevron 91. So today, I was running out of gas when I HAD to use Shell. I got the lowest one, I decided to pull out the manual... Does that mean that the engine can adjust without negatively affecting the car?


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[bronsin]

Probably.

My Honda ST1300 motorcycle calls for premium in the OM and on stickers near the fillup. But it runs fine on regular and the computer automatically adjusts the timing to prevent knock.

MAny of us ST1300 owners have ridden to northern Canada where premium is rarely found and we have no problem running using regular. In fact the majority of us dont use premium at all.

I DID use premium in my Yaris once and the next morning there were TWO of them in my driveway! Apparently it released the Higgs Boson in my engine, causing it to get pregnant.

[holly01]

subscribed, this seems like a very interesting thread

[ern-diz]

This is such a fuzzy topic of discussion for me.

There are those that swear 91 is better for your engine than 87 is. Then there are those that swear it is not. There are those that claim 91 is only for high compression, performance engines, while others say the 1NZFE actually runs at a pretty high compression (10:1, or something??).

I used 91 for the majority of my Yaris' life and switched to 87 more recently. Can't say I noticed a difference. I don't mind paying more and I don't mind paying less - what I do mind is doing the wrong thing for my engine.

I wish there was more of a consensus on what fuel we should be putting into these cars.

[Idahotom]

Put regular in it. Or premium or if it makes you feel better! All mine has ever gotten is regular. I don't waste 2 seconds worrying about which to use. ESPECIALLY at my altitude over 4500' ASL. My kitplane engine builder tells me to use mid range or premium if at sea level, but as most of my flying is at 4500 and way above, he told me to use regular, and he is a professional mechanic highly respected in his field. Around here its 35 to 50 cent a gallon difference, I have better things to spend my money on then gas meant for a higher compression engine.

[WeeYari]

Originally Posted by ern-diz

I wish there was more of a consensus on what fuel we should be putting into these cars.

Every consumer watch dog type of report will state using premium where regular is stated is throwing money away. The big gas companies are great at marketing the premium fuels as being superior regardless of the octane recommendation from the manufacturer. Of course they are. Look at the profit margins inherent in the price differential. In Canada, this is approximately $.20 per liter.

[tmontague]

The Yaris does run a relatively high compression but is tuned to not knock with 87 octane and is what is recommended by the vehicle guide.

Most higher performance cars that call for 91 can be run on 87 and not knock due to knock sensor which will result in retarded timing and less performance.

If the Yaris had a tuning map programmed in the ecu from factory then it would definitely be a difference running 91. That said if the Yaris had that map it would be advertised by Toyota. Toyota isn't going to tune a 91 octane map on a NA sub compact economy car.

The reason you get better fuel efficiency with 91 is that most 91 rated gas has no ethanol in it.

I ran 87 in the 370z I rented while in Mendocino on my honeymoon. The rental company said that's all they put in them ever regardless of it calling for 91. I hammered that car for 3 days on mountain/canyon runs and it had no issues other than less power than 91 fuel.

If a car has no 91 octane tuning map then you cannot take advantage of the advanced timing and more power you get from it.

You will however get better fuel efficiency (I know I do) but as Wee stated above, with 91 octane being $.21 /L extra it ends up costing more in the end.

Drive your car on the highway once a week, keep up with the maintenance including preventative and don't be afraid to go WOT every few weeks. You engine will be clean as can be and you only ever have to run 87oct.

I personally don't notice a difference in performance really switching to 91 other than better fuel efficiency.

That said I drive my car pretty hard every couple days and average about 5.6L/100km so I have no interest in 91oct.

[ern-diz]

That all makes sense, thanks.