What Grade Of Gas Do You Use?

[RadioHowie]

Wow, guess I'm waisting money, I only burn 93 octane. :huh:

Yep...complete waste of money.

In fact, 93 octane's greater volatility can cause driveablility problems with motors designed for lower octane.

Unless you're running 12.5:1 compression or higher, 93 octane is senseless.

 

[markjenn]

This is one of those things where you start with the OM unless there is a strong reason to deviate. The OM says 87. If the bike pings on this, you go up from there. It's really that simple.

- Mark

 

[yamahlr]

Actually think the bike runs better on the regular grade w/ the Iridium plugs. If the manual doesn't call for a specific grade above reg it's not necessary unless the bike tells you differently by the way it's running. I do however buy from a reputable station (Amoco) that over a number of years have not gotten bad gas from. They are also careful about draining residual left over gas from the hose (before it runs all over the bike)when they see me pull up.

 

[ibsunburnt]

Damn RadioHowie, that's puttin' the pencil to the paper!

 

[XJRGUY]

I filled up the last two tanks with 89 and the bike has been idling at 900/950 RPM instead of 1050 like it did with the 87.

Tried Mobil and now Chevron. Same result.

Will go back to 87 and see if the bike goes back to idling at 1050rpm like it always has.

XJRGUY

 

[Centerline]

87 or 89.

 

[sparky3008]

Funny I came across this after my weekend with the Harley guys.

I was talking with a couple that were convinced their bikes ran best on 93 even though the compression numbers didn't require it.

Of course there was no point arguing but these guys understood compression and its relation to octane but still said their bikes ran noticeably better on the more expensive stuff.

On my VStar that I had 10:6:1 pistons in I ran 93 but could have gotten away with 91 as they were designed to run on Kali pump gas.

I don't think a Harley engines compression is that high :haha:

Anyway I run 87 in mine and runs fine...

 

[JohnM]

Damn, I'm jealous. My old bike needs 91 or better according to the sticker on the tank. I've never even tried 89 or 87. Been paying about $3.29 here.

 

[sparky3008]

Compression numbers aren't everything, duration of cam and stuff like that determine it also. The fjr compression numbers are in the 10's but only requires 87 so if the bike says 91 it may well require it...

 

[markjenn]

Yes, CR is just a single factor in many affecting octane appetite. Cylinder size is another - I have a R6 with a very high CR and very high specific power output, but with tiny cylinders, that only specifies 87.

Air-cooled big twins are probably the worst case for octane requirements, even with modest CRs.

- Mark