08 wr 450 octane rating

Heard several different opinions on this and was wondering what the truth is before I fill it up and ride. Bought a 08 last week with only a couple hrs on it. All stock. Did the free mods, waiting on a couple other parts before I go riding. Most of my riding will be Baja with a some local So Cal canyon stuff in super moto trim. I know the bike has a high compression engine and have heard that you should always run Premium fuel (91) in engines with high compression to prevent detonation which can do damage over time.


Any info or past experience on running 87 vs 91 will be appreciated.





Your owners manual covers this well.

Premium Pump fuel from a busy station.

Always run 91+ I'm not sure about Cali, but here, regular fuel has ethanol, which is not very good for aluminium and brass carb parts. 

Your owners manual covers this well.

Premium Pump fuel from a busy station.

Guy couldn't find the manual when I picked it up. 

Premium pump gas only.

Same site, fewer steps:




Also, an alternative:




Note that the manual will call for 95 octane.  This, however is 95 Research Octane.  There are 3 major methods of denoting the octane rating of a fuel: Research Method (RON), which produces the highest numbers, but is not considered particularly realistic anymore, Motor Method (MON), which is considered most accurate, but produces low numbers for the same grade of fuel, and is therefore "not as attractive" from a marketing viewpoint, and "Anti-Knock Index" (AKI), which is an average of both methods, and is what you see on gas pumps in North America.  That's the little sticker you see that says, "(R+M/2)", or, "research plus motor divided by two".  95 Research Octane is roughly 86 Motor Octane, which comes out to an AKI of 90.5.


At extremely high altitudes, it is sometimes possible to run 87 (AKI) octane without detonation because the lower air density reduces actual cylinder pressures, but 91 will be required in most all situations.  The damage that can potentially be done by detonation is extreme, and not worth the tiny savings.


I have been riding in Baja for many years. In March and April, 2003, I made the ride (nearly all off-road and 1,500 miles crisscrossing the peninsula several times) from San Felipe to Cabo San Lucas on my then brand new Yamaha WR 450F. Once our group left San Felipe, premium gas was often not available. My stock bike, ridden conservatively through every kind of terrain Baja had to offer, ran just fine on both Magna 87 octane and Premium 91 octane fuel. One thing to remember, Mexican gasoline in Baja California does not contain ethanol -- absolutely, positively and recently tested in 2013 by one of the original owners of Maxima Racing Oils.

My recommendation to you is to always use 91 octane fuel whenever it is available, however. Use 87 octane if that's all that is available and ride easy. My son wanted to save a few cents per gallon of gas and blew up the motor on his 2004 Yamaha WR450F, running California formulated (10% ethanol) Regular 87 octane gas exclusively. He rode hard and often could be found at the sand dunes at Glamis, as well as Superstition Mountain -- "penny wise and pound foolish". Older, wiser and poorer, he replaced the 2004 with a new 2008 model WR and fed it Premium gas only.

I currently own a 2008 model WR that only drinks 91 octane Pemex Premium gasoline and loves it. While the gas in Baja has become a little more expensive than gas in S. CA, my overall cost for fuel is actually lower using Mexican gas. This is because I see higher MPG using Mexican non-ethanol blend gas and I don't have the added cost of fuel stabilizer.

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