Better gas mileage with 89 octane!

[aRs3N1c42]

Here's an article about octane

http://auto.howstuffworks.com/question90.htm

Notice where it says "or some other combination of fuels that has the same performance of the 87/13 combination of octane/heptane". Since the refining process of crude oil cannot completely separate all the hydrocarbons into pure octane and pure heptane. Gasoline typically is a blend of many different hydrocarbons, alcohols, detergents and solvents to keep your engine clean and running well. The Octane rating on the pump is more often a comparison of the gasoline's performance to an actual octane/heptane solution produced in a laboratory.

My Organic chemistry professor in college explained all this to us, but since it was a 9:00 class, I wasn't completely awake most of the time. And since I never took great notes, I could be wrong. I'm still reading the articles on howstuffworks.com. I may post back with an update... 8)

[Poot]

I also prefer the 89 octane, over 87 , and 91. I've used the 93/94 but only when cruising at high speeds for long durations.


91 octane seems to jumpy, and 87 octane doesnt seem to make the engine as smooth as possible.

at least for my 850



poot

[DaveDanger]

Gonna add my 2 cents worth here as well To be understood is that aviation fuel is not accurately graded by octane rating, it is a performance rating. Nevertheless, it does what it does rather well. I will refer to "octane" here because that is what the fuel trucks are labelled as, and what it's called in the industry.
Aviation gasoline can be gotten in ratings as high as 130 Octane. The typical stuff obtained at the local airport will almost always be what is referred to as 100LL, it has a beautiful sky blue color. For aircraft usage, it really is "low lead" fuel. For automotive use, it has more lead than the fattest pencil ever pulled from inside your 3-ring binder at school. The 130 octane grade is refined in limited quantities anymore, but is used almost exclusively by the racing and aerobatic aircraft crowd. It has a deep purple color. Aviation 87 octane is almost unheard of anymore, causing a whole slew of engine problems due to the lubricant properties that are no longer provided... but that's a whole 'nother post on a different board I make no claim to exactly what the refining techniques that are used and exactly how the actual octane of avgas compares to autogas, but every dirt-tracker in the country can't be too far wrong when they cue up their 55 gallon drums at the gate to the local airport fuel farm on friday afternoons. In general, I have rather good access to Avgas in my daily grind, (I occasionally have to drain an aircraft fuel cell to perform maintenance and not many owners want the fuel pumped back into the plane after its been stored in just any old 55 gallon drum... Is it my fault that I keep very clean plastic drums around? I'm not gonna argue with them!) and frequently will filter a gallon or two into the bike's tank before I head to the local Saudi fuel outlet. The mixture of my 100LL and the regular 87 from the pump provides me a rather nice acceleration, lack of ping under almost any load, and just seems to kick me in the butt a tad harder than when it's plain 87. That may be my tiny mind wanting to justify the effort I went to to accomplish the goal. I do try to avoid going above a 50/50 mix of Avgas to autogas, just because it seems to run a bit hotter, idle faster and in general reaches a point of diminishing returns. During WWI, it was discovered that you can add a chemical called tetraethyl lead (TEL) to gasoline and significantly improve its octane rating above the octane/heptane combination. Cheaper grades of gasoline could be made usable by adding TEL. This led to the widespread use of "ethyl" or "leaded" gasoline. When lead was banned, gasoline got more expensive because refineries could not boost the octane ratings of cheaper grades any more. Airplanes are still allowed to use leaded gasoline (known as AvGas), and octane ratings of 100 or more are commonly used in super-high-performance piston airplane engines. In the case of AvGas, 100 is the gasoline's performance rating, not the percentage of actual octane in the gas. The addition of TEL boosts the compression level of the gasoline -- it doesn't add more octane.

[Buffalo Breath]

GaS

Silly Boyz, I thouht every one on two wheels ran nitro, oh yea it will give you a horse power boost with out more compression or boring, but the mileage really sucks, AHHHH I love the smell of Nitro in the morning!!!

[Clone]

Speaking only about my bike:
Premium 92or93 depending on the station = worst milage
Mid-grade 89 usually run get in the mid 40s
Regular 87 run once in a while when I fill up in the boons = best milage 46 or more
But I usually am riding in temperatures below what you get in the states, a nice day is 20-25C, most days 15-20C.

Reading "how stuff works" I get the impression that a lower flash point would mean that a fuel burns faster,
so 87 should burn better than 89, 89 better than 93
Do I have that right?
Then shouldn't 87 pack more power than 93?

[DaveDanger]

Negative Clone, lower flash point means that its fumes will ignite spontaneously at a lower temp, not necessarily burn at a sustained hotter temp. Read that "How Stuff Works" again, and you'll see that octane rating has to do with how much a specific fuel can be compressed before it ignites simply from pressure. I'm doing a bit of additional research to see if I can support my owns verbal meanderings here, but I feel that the higher the octane, the higher the sustained burn temp. I will repost as I learn

[mcycle-nut]

Re: GaS

AHHHH I love the smell of Nitro in the morning!!!

Ah, so YOU'RE the nutball that was SIR a few years back standing right behind a top fuel dragster while they spun it up after a rebuild inhaling deeply the fumes going, "YES, YES!" while everybody else was running away covering their ears and trying to breath air! :roll:

Oh, by the way. My EZ pings like hell on 87. It doesn't on 91, and yes, the timing is spot on. 8)

[Clone]

I got the part about igniting at a lower pressure,.
My question and point is that if a fuel is more ready to ignite, that to my mind would mean it is faster burning and would pack more power.
In an aircooled engine do we really want a fuel that burns hotter?
Faster would be better in my mind.
But I'm always willing to learn why I am wrong. 8)

[RichSPK]

The kicker is that you need a *controlled* burn to make power, not necessarily a fast burn. You want a burn, not an explosion.

[Pete Logan]

Just in passing, when my father was in the RAF he had a friend who ran his Daimler Majestic on aviation fuel. Not sure what the rating was, it was referred to as JP2.

It went like a rocket for 10,000 miles, then the engine blew up.

Pete

[AOD]

I've used the 93/94 but only when cruising at high speeds for long durations.

You really wouldn't need the 93/94 when cruising at high speeds and long hauls. You won't be accelerating much, you have good airflow for cooling...etc.

~Adam

[DaveDanger]

Pete, your dad's friend must have had a diesel engine in that majestic... JP2 or any fuel that has a JP in its designation is Jet fuel... the JP stands for Jet Propulsion. The numbers after it stand for the various grades and improvements made to it as time went by. JP8 is sort of the standard today. Jet Fuel is in its most basic form... kerosene. I burn JP8 in my kerosene heater in the hangar on those chilly days during Georgia's winter... Jan 23rd thru Feb 4th My Dad had a Diesel Peugeot 504 during the fuel crisis of the late 70's and it thrived on the jet fuel we sumped from the trucks at the airport when we could get it. The JP fuels have almost zero additives in it that a standard diesel engine would need, so a lot of fuel filler neck blending has to be done to use it for an extended time

[Pete Logan]

Think I must've got the story wrong 8) It was 30 or 40 years ago.

Pete

[Anonymous]

And yes there is 110 octane gas. The gas station near my local dirt race track sells it as race fuel. I couldn't afford to run it in my bike though. It should never cost me more than $10 for a tank of gas.

Hey, spare a thought for us poor UK bikers, gas is 98pence ($1.72) per litre :x

[dpep]

I get the best mileage from Shell's premium gas, whatever it is called. I have no explanation why, but I am a compulsive mileage checker and that has consistently proved to be true for me. It may be different for others, though I have a friend with a Harley touring bike that reports the same thing for him.

In general I do find that higher octane gas gives me slightly better mileage. That is important to me on trips when I am trying to stretch the length between fuel stops. But the main reason I use high octane gas, particualry in the summer is to guard against pre-detonation. It is so harmful to an engine that I don't mind paying for a little insureance. I will use lower octane when the riding I expect to be doing and the air temprature warrant it.

If your bike is pinging, move up in grades until it stops.