The last gas question

[Tonavi]

I know octane and gas questions have been covered elsewhere on the forum, but in all of those threads there isn't a clear answer on the subject.

I bought my hatch in August 2007, and from the day I drove it home on the first dealer-bought tank of gas, noticed what sounded like a valvetrain rattle or something like that. I continued to put in regular 87 octane gas and the car kept rattling, and it was very easy to hear with the windows down.

After talking to a mechanical engineer, I tried using the 89 octane stuff to quiet things down, and the car runs noticeably smoother and is silent. My first tank of 89 was at 1600 miles, and now I'm at almost 21,000.

I was reading a Fit forum on FE when I read a post that was about how using higher octane gas could slowly wreck your motor over time by burning too hot and causing timing problems. That's when I went on Google and started researching. Let me note that switching from 87 to 89 resulted in no gain in mileage that probably wasn't related to the break in period. I get between 38 and 44 normally.

Is it true that using +2 octane gas causes carbon buildup and such? If that's the case, wouldn't running Seafoam every 10,000 miles keep things clean and more efficient? If anything, premium is a waste of money, but the extra $0.03 seems to make a difference in the drive.

[ChinoCharles]

The bottom line is that Toyota designed this car for regular old 87 pump gas. Says it in the owner's manual.

[Tonavi]

Originally Posted by ChinoCharles

The bottom line is that Toyota designed this car for regular old 87 pump gas. Says it in the owner's manual.

Specifically, the manual says "minimum required." So that must mean that using a grade higher will do no harm? Not like I'm using race gas or anything.

[ChinoCharles]

AH! Semantics. Does that mean minimum required, like, put at least 87 in it, or does it mean minimum required, ie: it requires the minimum.

The real, meaningful answer: I don't know one Toyota engineer that belongs to Yarisworld. Take the rest of this thread with a big, giant grain of salt and do what makes YOU happy.

[PetersRedYaris]

Originally Posted by ChinoCharles

AH! Semantics. Does that mean minimum required, like, put at least 87 in it, or does it mean minimum required, ie: it requires the minimum...

I would think it means "put at least 87 in it", since many parts of the country have grades far below 87 octane. 85 is the low here...

[Tonavi]

I guess the only way to test it is to run some seafoam through the vacuum line and judge the carbon by the smoke....

It would be interesting how dirty a car can get in 21,000 miles regardless of fuel type though...

[ChinoCharles]

It was a joke, Peter. Jeez.

[PetersRedYaris]

[Tamago]

Originally Posted by ChinoCharles

AH! Semantics. Does that mean minimum required, like, put at least 87 in it, or does it mean minimum required, ie: it requires the minimum.

The real, meaningful answer: I don't know one Toyota engineer that belongs to Yarisworld. Take the rest of this thread with a big, giant grain of salt and do what makes YOU happy.

well since 87 is the minimum available how would you put a lower octane fuel in the car?

[Tamago]

Originally Posted by PetersRedYaris

I would think it means "put at least 87 in it", since many parts of the country have grades far below 87 octane. 85 is the low here...

where can one get 85?

[frownonfun]

here

[1NZYaris1]

the lowest octane rating for New Zealand petrol is 91 then 95 then 98 and speacialist garages selling 102 (rocket fuel)but most sell 91,95 or 98

[Tamago]

Originally Posted by frownonfun

here

ahh

and it's not E-85?

[frownonfun]

Originally Posted by Tamago

ahh

and it's not E-85?

i don't think so... goes 85, 87, 91 here. i seen some signs on a few pumps that mention the gasoline "may be up to 10% ethanol" but none specifically say E85 or anything.

[Tamago]

Originally Posted by frownonfun

i don't think so... goes 85, 87, 91 here. i seen some signs on a few pumps that mention the gasoline "may be up to 10% ethanol" but none specifically say E85 or anything.

ok

interesting!

and no, 10% ethanol and E85 are not the same thing :)

[jambo101]

Originally Posted by Tonavi

I was reading a Fit forum on FE when I read a post that was about how using higher octane gas could slowly wreck your motor over time by burning too hot and causing timing problems. .

Thats backwards ,,the higher octane burns cooler than lower octane thus the carbon builds up ultimately choking your engine and oil with carbon and sludge build up.You might want to check your timing for that rattling you are hearing as the car should run smooth and quiet on regular octane gas.

[Tamago]

Originally Posted by jambo101

Thats backwards ,,the higher octane burns cooler than lower octane thus the carbon builds up ultimately choking your engine and oil with carbon and sludge build up.You might want to check your timing for that rattling you are hearing as the car should run smooth and quiet on regular octane gas.

actually no.

higher octane fuel is less likely to detonate prematurely. this means it doesn't burn when it should without a timing/spark advance.

without a way to advance timing, higher octane fuel will cause your engine to run a little hotter (ever run a briggs and stratton on 93 octane? after awhile you'll notice the header will be glowing red hot)

[MUSKOKA800]

I would suggest that if your engine "rattles" on regular octane fuel then it has a problem that your selling dealer should have repaired (warranty?).
I'm no mechanic but can't imagine how different fuel could "fix" a valvetrain noise. But a KNOCK/pre-ignition yes. Improper ignition timing may cause pre-ignition which might be remedied by higher octane.
My question to the dealer would have been "why is the engine rattling?".