85 Octane in The FJR

[LAF]

Well in my 3500 mile adventure I have discovered that CO, UT, has 85, 87, 91 at the pumps. SO I had used the 87, but got curious on the 85 and tried it. I have seen no issues and am getting about 47 MPG on it.

So any issues, or problems running it? It seems performance and mileage has not suffered.

Thoughts would be good.

 

[majicmaker]

No issues at all with 85. Cheaper too.

 

[LAF]

No issues at all with 85. Cheaper too.

Thanks for the reply I did not think there would be, dont want to line up at a light and try to out run someone, but for 80 MPH running it seems just fine.

And yes it is way cheaper out west here.

 

[Bounce]

No issues with lower octane unless there is. It's an thing within fuel to prevent pre-detonation (knock). If you don't have knock with the lower octanes then there's no need to spend more money on the higher ones. The benefit is that the octane works to resist detonation, so that means it's harder to set off in the combustion chamber the higher the rating. Some (like you noted) get better mpg from lower octanes than higher ones. So... better mpg, lower price, no knock: the only reason to buy higher octane if if the motor is a higher compression combustion chamber that requires it.

for years i was mislead into thinking that higher octane meant more "power" when it's nearly the opposite. a gallon of one has no more energy than a gallon of the other. it's also not "better". it simply resists pre-detonation at higher compression ratios. so why spend more for something you don't need?

i even bought a tank of 101 octane PUMP gas when in OKC once (there's still one place on the north side that sells it). the reason? so i could mention it in threads like this. it got no better or worse mpg in my 2008 Subaru STi than the 93 octane its high-compression, turbo, stage 2 motor was tuned to use (ie: it doesn't knock at 93 octane, so it also won't knock at 101 at twice the price). meanwhile it cost me more than $6 a gallon for the bragging rights.

 

[Auron]

I live in CO, and am considering using 85. Doesn't higher altitiudes offset the need for higher octane?

And I take it the FJR does not have a knock sensor?

 

[C&C]

All other things the same, higher altitude does reduce the need for octane. And as for requirements for higher octane, there are other factors, besides higher compression engines (though that is one of the variables); others can include type of fuel injection, shape of the combustion chamber and temperature of the incoming charge.

 

[Mount Rainier]

Timely post. Thanks

I just returned from an 11 state trip, and, were available, I too used the 85 obtain (even a couple of ethanol free locations along the way) with no apparent ill-effects. Over all,(4300 miles) I averaged 47+ mpg. Very happy with that mileage.

Keep Going!

 

[Road_Runner]

I live in CO, and am considering using 85. Doesn't higher altitiudes offset the need for higher octane?

And I take it the FJR does not have a knock sensor?

Yes they actually provide the 85 octane for faster burn resulting is less emissions. 85 at high altitude acts like 87 at low altitude.

From: Wiki Octane

"United States: in the US octane rating is displayed in AKI. In the Rocky Mountain (high elevation) states, 85 AKI (90 RON) is the minimum octane, and 91 AKI (95 RON) is the maximum octane available in fuel[citation needed]. The reason for this is that in higher-elevation areas, a typical naturally aspirated engine draws in less air mass per cycle because of the reduced density of the atmosphere. This directly translates to less fuel and reduced absolute compression in the cylinder, therefore deterring knock. It is safe to fill a carbureted car that normally takes 87 AKI fuel at sea level with 85 AKI fuel in the mountains, but at sea level the fuel may cause damage to the engine. A disadvantage to this strategy is that most turbocharged vehicles are unable to produce full power, even when using the "premium" 91 AKI fuel."

 

[garyahouse]

SO I had used the 87, but got curious on the 85 and tried it. I have seen no issues and am getting about 47 MPG on it.

So any issues, or problems running it? It seems performance and mileage has not suffered.

Thoughts would be good.

Reprinted from an earlier post I made:

Octane class 101

You'd be surprised how many think higher Octane produces more power in EVERY engine. Octane is tricky to understand. Years ago, my autoshop teacher put it like this: Lead (shows how old I am) is like "slow 'em down juice." It slows down the explosion. It enables fuel to endure higher compression without self-igniting, and slows the flame front once it does ignite. Think of it like you're diluting the fuel. Truth is, higher Octane = poorer performance, with one exception: the only time higher Octane improves performance is when the engine's compression is too high for regular. In an engine where compression is too high for regular, the flame front moves through the combustion chamber too quickly, slamming the piston while it's still on it's way up, causing "knock." This is very destructive. It sounds like ping pong balls in the engine. Side note: if you give a hot FJR too much gas at real low RPMs, you'll hear this. It's loud, distinctive, and destructive. Anyway, higher Octane slows down the burn, sorta calms down the gas. Truth is, it produces LESS power, ounce for ounce, than regular... in an engine designed for regular. Modern electronics make up for these issues and prevent knocking by altering timing and etc., but the result is the same. Use the lowest Octane gas for the most power. Obviously there's a lot more to it than that, and I'm sure others on this forum can explain it better, but you get the idea. For what it's worth, adding anything to gas produces less power. Ethanol kills power as well, when mixed by the ECU at normal gasoline ratios (ECU, which stands for Engine Control Unit, controls the fuel injection ratios). That's why engines make less power and get poorer gas mileage when using higher ratios of Ethanol, like that found in E-85.

Gary

darksider #44

 

[user 28727]

Last week I rode 4 days in the Black Hills of South Dakota, and some places have 85 Octane, 87 octane\ with ethanol, and 91 octane.

85 octane pumps are supposed to say something like Sub-standard gasoline may cause engine damage-Please consultant your owners manual.

I went the other way and used 91 without ethanol, At $3.89 a gallon. On board computer showed 47-52 mpg.

87 octane real gas in Bismarck, North Dakota is $3.99

kup1236

 

[RPrice]

This is a very informative thread, Thanks!!

 

[wfooshee]

I live in CO, and am considering using 85. Doesn't higher altitiudes offset the need for higher octane?

Exactly this. The three grades there give the same knock resistance as the three "higher" grades we flatlanders get, due to the higher altitude and lower atmospheric density. It's not "substandard" or anything like that.

But if you fill up in Denver while headed east, you'll not want 500 miles worth of gas.... You'll want the higher octane again as you drop in elevation.

 

[LAF]

Thanks Guys. Into AZ now so 87 it is.

However 88.5 at pumps through me for a loop.

I saw no ill effects on 85 but I played as high as 12,000 feet, and a lot in the 8-6,000 range no problems.

Glad the discussion helped others.

 

[user 28727]

I was wrong. I did a search to what the label is to say at the pump of 85 octane in South Dakota.

"Sub-regular octane — refer to owner’s manual before fueling.”

kup1236

 

[Big Sky]

In Montana, 85.5, 87, 89 and 91 are common. I'm frugal (okay, a cheapskate) so have routinely burned the (cheapest) 85.5 over about 85,000 miles. Once in awhile I fill with the 87 or 89 to see if I notice any difference in performance, engine temp, power, mileage, etc. and never do. I even buy a tank of the premium once in awhile - same story, no really discernible difference. I have a friend who has an '08 AE whose mechanic told him, nope, gotta run the premium 91, so he does it. I've told him the owners manual says 87 is okay, and that personal experience indicates the 85.5 is okay, too. He still spends for the 91... That's about $1.20 more per tank than I pay.

 

[Spud]

Whatever's cheapest at the pump works just fine in these bikes (as long as the nozzle is black, not green ).

 

[FrankJR]

I run 85 octane and I have had some engine knock at low rpm in 2nd and 3rd gear. Nothing that an upshift wont fix, but it is there.

 

[SuperFLY91]

Wait...hold on here...you mean all summer long I've been buying 91 octane for no reason??

Who do I talk to about a refund?!? :dribble:

Should I just go to my local gas station and demand some money back??

 

[majicmaker]

Wait...hold on here...you mean all summer long I've been buying 91 octane for no reason??

Who do I talk to about a refund?!? :dribble:

Should I just go to my local gas station and demand some money back??

Good Luck with that! But, isn't it nice to know that 85 works just fine?