Question regarding octane

[ColoradoFJ60]

I know my user manual states to use 87 octane but here in CO the low grade is 85, mid is 87. I know it's only a .10 difference but is it ok to drop down?

I do put 87 in right now but I sure wouldn't mind saving that $2.xx per tank.

Is it bad to drop?

 

[EarthX]

I know my user manual states to use 87 octane but here in CO the low grade is 85, mid is 87. I know it's only a .10 difference but is it ok to drop down?

I do put 87 in right now but I sure wouldn't mind saving that $2.xx per tank.

Is it bad to drop?

That small of a drop wont make a difference in the original motor. I would not worry about it.
Me on the other hand......I need to put 91 in mine due to my supercharged 350....one, if not the only draw backs to my superchager.

 

[DocB]

Octane simply indicated the fuel's ability to resist exploding. Higher octane, more stable and resists exploding and therefore resists pre ignition, also called ping, also called detonation. Try the lower octane; if you do not get a ping noise (like marbles thrown into the motor) while accellerating up hills, etc, then you are fine. If your engine makes the noise, then go back to higher octane. (PS the reason some motors require higher octane is that they use higher compression ratios to obtain power; higher compression equals higher heat; higher heat equals tendancy for fuel to explode too early; therefore the need for detonation resistant fuel, therefore higher octane fuel.)

 

[Mark W]

A stock 2F should run on Tijuana ditch water. It should be perfectly happy on 85 octane.

Mark...

 

[Tinker]

And I thought it needed 91...

 

[swank60]

And I thought it needed 91...

You might need a higher octane fuel if you have a lot of carbon build up or your timing is set incorrectly (which causes the pinging)

Try dropping back and see what results you get. I've tried higher and lower octane gas in my truck and it never makes a difference. (Our Avalon, on the other hand, is another story. Runs much smoother on the higher octane gas)

 

[ColoradoFJ60]

cool, thanks guys.

 

[COSkier]

There's something to do with the altitude too. It's been 15 years since I took thermodynamics, so those brain cells are long gone, but you can get away with lower octane due to the lower pressure. I think. Anyway, I run all my cars on 85 octane, since I live at 8800', w/o pinging or knocking. I'm sure 85 is fine for Denver area too.

 

[CATMECH]

At low altitudes the air is thick or dense wich actually will boost your compression. If the compresion is high enough the fuel will ignite on its own under pressure. Just like a diesel engine. At higher altitudes you can run a high compression engine on low octane fuel and not have any problems, because your compression wont be as high allowing you to use a less stable fuel. Any way my 60 runs fine on low octane at any altitude.

 

[kevin g]

I agree with the majority. I run 85-octane in my vehicles also. My cruiser and camry do fine with it. The only vehicle I have had since living in CO that I didn't run 85 in was my old Tacoma.

 

[Liam]

I run 91 in everything(78fj40, 87fj60, and 98-100series), but of coarse my work pays for it all