I would appreciate your thoughts on this. Here in NE Ohio 90% of the gas stations carry 89 and 93 octane gas (please don't get me started on the 10% ethanol bullshit). There's a considerable cost difference between them normally. Of course my new RK specifies 91! I've used both and not noticed any difference, no knocking or pinging. Do you guys see any reason to pay the extra money for the 93? I know it doesn't seem like a big deal for one gallon, but over the course of a riding season .30-.40 cents per gallon adds up and I don't like paying for something I don't need. Input please? Thanks!

 

I'd always choose to go 2 points over than 2 points under requirement all day every day..gotta' pay to play and I believe it's better for your engine and stick with Top Tier. that being said, I went fishing with the owner of a Chevron station once and he said their fuel is rated conservative, specifically that when tested it always rated higher than the pump octane rating..no reason to believe he was FOS..nonetheless I always use Premium because I'm OCD and unconcerned about the cost

 

I always use the best I can get and mine still knocks. I also try to go to Orville and get ethanol free gas when I can.

 

Mix it 50%/50%, and you'll have 91.

Gawd...I wish I could get 93.

This has been discussed sooooo many times, here's my summary.

- Octane resists detonation. It does not generate more power. If your engine is higher compression, it could pre-detonate lower octane gas.
- Harleys have detonation protection. So, if the ECU detects pre-detonation, it will retard the timing to reduce pre-detonation. The side effect is somewhat reduced power.

BTW...FWIW...my TG with 255 Cams seems to like Shell the best.

 

You're gonna bring out the Octane police any minute. I run what ever is highest octane.
But I will add this:

 

I've ran 89 in all my Harleys (stock) going back to 1988 Low Rider up to my 2014 TG. Not one problem yet. Even ran 89 in both my Vettes - except on race day.

If your manual says "recommends" you can safely use 89 - if your manual says "requires" then you have to use premium. I have half a dozen newspaper auto column reports and numerous auto/bike magazine articles that agree.

If you run other then stock you may need premium or if your bike pings on 89 or 91.

But it's your bike - do what YOU feel comfortable with and never mind what others tell you to do.

 

Thanks for a useful reply!

 

Cant say for certain but the M8 might come with knock sensors and retard the timing if it sees detonation ( cant see why it wouldn't) . If that's the case, you may not really "see"any difference other than less power but only under big load. If it doesn't have knock sensors and your still not hearing it beat itself up on lower octane, the new combustion chamber afforded by the 4VPC layout and dual plugs may tolerate it fine through nice controlled burn. I'd stick with min 91 if you can regardless. Just my opinion.

 

Good post, thanks! I'm sure it has knock sensors.

 

Thanks for the replies, I think that as long as everything is stock 89 is fine. Probably while on the road 91 will be an option, just not locally to me. Traveling yo take what you can get.