[velosaurus]

Is there a recommended fuel type for the EFI Enfields?  (Presumably there is already thread about this, but I'm having no luck using the search bar.)

[Arizoni]

The Royal Enfield is a low compression (old fashioned) engine that runs nicely on Regular grade (87 octane r+m/2) gasoline.

I have used the 10 percent alcohol fuel in my 2011 G5 for 3 1/2 years without any bad effects.

IMO, its best to stick with a name brand gasoline because many of them (like Chevron) has fuel injector cleaners in it.

If you use a El-Cheap'o brand fuel, plan on buying some fuel injector cleaner about once a year to keep your injector clean.

[pmanaz1973]

I run a ethanol-free fuel - 89ish octane. 

This can be a bit tough to find and a bit more expensive, but from all accounts worth it.

When the search funciton is revived, look it up on this forum and most guys will recomend the ethanol-free fuel.

I've been fortunate to live in a area where I have a few pumps of ethanol-free fuel easliy availible, so I've run it in my last couple of bikes.

[Mr.Mazza]

Ethanol can be bad for rubbers and such in fuel systems not designed for it.
It also reduces the power of each stroke and therefore range.
Id advice using a slightly higher than standard octane whereever you are. Here low is 91 high is 98 or 100, so the lowest I run or my friends run is 95.

Price difference is piss all for 15L.

[pmanaz1973]

Id advice using a slightly higher than standard octane whereever you are. Here low is 91 high is 98 or 100, so the lowest I run or my friends run is 95.

+1  if you can find it.  I asked our local commercial fuel guy if he he can get 92 or better and he says he is going to give it a try and see how it sells.  Most of the ethanol-free fuel around here goes into small engines, and off-highway vehicles. I think it will sell...we'll see.

[Kevin Mahoney]

You can run any RE on almost anything you can get to flow into the petrol tank that is sold as gasoline. 85-89 with 10% ethanol is no problem. The materials are made for it.
E-15 which the administration is pushing is an entirely different matter say ALL engine manufacturers. 

[High On Octane]

I have to mix E85 with 91oct to get my dirty pig to run right.  But I'm also running higher compression than stock.   

[Kevin Mahoney]

OMG - Why are you running E-85? I don't think that is a good idea at all.

[High On Octane]

OMG - Why are you running E-85? I don't think that is a good idea at all.

Because it's cheaper than 100 octane race fuel.  I did some research, if I incur any problems, I'll be sure to report.  But so far the bike runs very well with the mix.  It's a 25%E85-75%91oct mix, so not pure E85, it's a blend.

[Kevin Mahoney]

I am risking reprisal here but at least here in corn country where the farm lobby has perpetrated one of the biggest hoaxes of all time in the public  - Ethanol.......the price of E85 does not compute in relation to the reduced mileage.

[High On Octane]

No one said ethanol was economic.  It is performance in a pump!  Its poor man's methanol!  E85 is roughly 105 octane, making it a very desirable fuel for high compression applications.  It is commonly used for turbo applications because it allows the user run more boost while the engine actually runs cooler.  There are downfalls tho, mainly being that when using pure E85 the user needs to tune fuel system 30% richer than regular fuel.  E85 is also slightly corrosive like methanol and extra care and precautions must be taken.

BY NO MEANS AT ALL DO I RECOMMEND ANYONE USING E85 IN THEIR ROYAL ENFIELD!!!!!

But as not to get sidetracked, really any pump gas is just fine for a stock Bullet.  Ethanol free or 10%, t doesn't much matter as long as it is quality fuel.

[velosaurus]

Thanks for the replies, folks.  Seems like I'll be fine with fuel from the local Chevron/Mobil. 

And I hope search functionality comes back to the forum soon.  I want to keep my Bullet happy.      

[crock]

Use 91 octane instead of 87 or 89. If nothing else, every fuel processor puts more cleaning compounds in their premium fuel.

[flyboy]

Correct me if I'm wrong, but I'm under the impression that the higher octane fuel will burn/ignite quicker than lower octane. Hence, would fire just a tad too soon in a stock set-up Bullet. I'd think you'd be OK with higher octane if the timing was set for it, but why? I think 87 or 89 would burn just fine with stock set-up and low compression piston.

[Arizoni]

Higher octane fuel does not ignite faster than lower octane fuel.
It gives no more power and it doesn't burn hotter.

Octane ratings basically rate how sensitive the fuel is to detonating or pre-igniting due to heat and pressure.  The higher the octane number is, the less chance of it doing these things.  The lower the number, the more likely these things will happen

Pre-igniting is the fuel lighting without the spark plug firing and it's due to high engine heat or high temperatures caused by compressing the air/fuel.
Detonation which can occur after the spark has initiated the fuel burn is due to the very high pressures that build up in the combustion chamber causing the fuel beyond the flame front to self ignite, usually in an explosion.

The reason high octane fuel is needed in higher performance engines is because these engines almost always have a high compression ratio.
High compression ratios create more heat during compression and if the fuel octane is too low the fuel will ignite just from the pressure before the spark occurs.

Stock Royal Enfields have a rather low compression ratio.  In the case of my 2011 UCE powered G5 it is 8.5:1.
This works fine with the 87 (R + M)/2 octane fuel but if the octane rating was much lower and I was using the engine power to accelerate or to climb a steep hill even this low compression ratio could cause pre-ignition or detonation.

[High On Octane]

Arizoni is spot on.  That is why I needed to raise my octane because I now have cylinder pressures at 150psi.  And honestly, the stock bottom end can't handle anything higher than that.  So I'm flirting with disaster, but it makes life more exciting for me. 

FWIW  I have always run 91oct in every bike I have owned since I was a kid and I very rarely have any fuel issues ever.