Does higher octane boost mpg?

Hello everybody, I'm currently getting approximately 48 mpg. I use 87 octane. I'm just wondering if use a higher octane will increase my mileage per gallon? Would I get any better performance with a 89, 91, or 93 octane fuel?

Chas

No. Dont waste your money on higher octane fuel, but do buy your fuel from a "Top Tier" fuel supplier rather than the cheapest place around.

Monitor your riding habits. Make a concious effort to keep your RPMs below 5,000 RPM. You'll notice a difference.

Tim

I agree higher octane fuel is a waste of money except for the very high performance vehicles.Most fuel mileage is governed by the right foot or right hand.Let the transmission do the job and the speed will increase with moderate increase of throttle.The use of ethanol has reduced fuel mileage,but fuel without it is rare and usually more money. Howard

Forty eight MPG isn't bad for a SW in town riding. It should average somewhat better on back roads where there aren't so many stop and goes. It should also show a bit more mpg on the freeway as long as you don't have to push it over 70mph or so.
Higher octane fuel doesn't directly improve mileage or power if the engine doesn't call for it. It all depends on the engine's compression ratio. Higher compression can cause detonation or pinging so those engines need higher octane fuel. My C650GT unfortunately is one of those that needs the mid grade fuel but the SW doesn't, lucky for it's riders.
The main determinant of mileage and power from a given amount of gasoline is the BTU rating. Ethanol reduces BTU content so fuel without the stuff will improve the mpg about 8-10%. Differing octane ratings don't change BTU content appreciably so that won't effect the mileage as long as the engine isn't pinging or knocking. I don't remember if the SW has a knock detector that reduces the ignition advance when excessively low octane fuel is burned in it. If it does then very low octane fuel would show less mileage because of the spark retardation that was preventing ping. Something like 80 octane aviation gas might cause a problem like that.

On my trip to the Haynes Museum a couple of weeks ago I inadvertently topped up (half a tank) with 97 octane petrol instead of 95.
I may have been disconcerted by the extra cost and my carelessness but I'm certain the bike wasn't running as well as usual until I filled up again.

I understand the engine's set up to run on a particular grade of fuel so here in the UK I use the recommended one, the cheaper one!

I think the lowest octane you can get in the UK is 94.I usually use 95 octane,as our gallons are different to US gallons, I am currently getting 64_68m.p.g. I keep to the speed limits and normally cruise along at 50_60m.p.h.

I once inadvertently filled up my Burgman 400 with lower octane 91 instead of the usual 95 over in Germany.  I didn't notice any difference in performance running on the lower octane fuel and filled up again the next day on 95.

Old Limey wrote:

I think the lowest octane you can get in the UK is 94.I usually use 95 octane,as our gallons are different to US gallons, I am currently getting 64_68m.p.g. I keep to the speed limits and normally cruise along at 50_60m.p.h.

  The gallons and octane ratings are both different, so one should look at where the poster is located when doing comparisons.  And yes, our system is better.
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I'd say most of the garages round here (in the South and South-West) sell only 95 and diesel.
That's part of the reason I was confused.

I haven't seen 94.1 for years.

In MN our regular gas has an octane rating of 87 and that's what I use all the time. I average 50 mpg. It goes up a mile or two if I drive slower and down a mile or two if I drive "happy".

First aren't there 2 ways of measuring octane??

European one gives higher number.

SilverWing is set up to Run on 87 US method. I have found gas mileage same or about same, Reg or high test.....Long trips and unsure gas quality, every 1000 miles or so I tank with Super Shell---if nothing else, cleaning effect....if the ads are true

Here's an excerpt from a wiki article on the difference of gasoline ratings in North America and elsewhere.

Anti-Knock Index (AKI) or (R+M)/2

In most countries, including Australia, New Zealand and all of those in Europe,[citation needed] the "headline" octane rating shown on the pump is the RON, but in Canada, the United States, Brazil, and some other countries, the headline number is the average of the RON and the MON, called the Anti-Knock Index (AKI), and often written on pumps as (R+M)/2). It may also sometimes be called the Posted Octane Number (PON).

Difference between RON, MON, and AKI

Because of the 8 to 12 octane number difference between RON and MON noted above, the AKI shown in Canada and the United States is 4 to 6 octane numbers lower than elsewhere in the world for the same fuel. This difference between RON and MON is known as the fuel's Sensitivity,[4] and is not typically published for those countries that use the Anti-Knock Index labelling system.

For the whole article:

https://en.wikipedia.org/wiki/Octane_rating

Good post exdavid. The short of it no more octane doesn't do it unless you have the compression to make use of it, one of the reasons Ethanol is a waste in a otherwise good fuel, pure gasoline. Former G Wing owner here using anything more than 87 oct. here may result in carbon build up.

Higher octane fuel per se will not boost mileage. Buy gas for any of your vehicles from a dealer who obviously has a high volume business. You will be buying fresher gas that is less likely to be contaminated.

I use non alcohol octane 93 the price is a non issue so why not use the best. i ride lot of hills and avg 60-70 mph, i am 250, the wife is 145 .. i get 60 MPH with my silver wing

I hope I am not adding fuel to the fire (pardon the pun) but I have a friend that has a Honda 125 used strictly for racing and they all use same higher octane fuel to keep them at the same horsepower.
The lower octane fuel is slower burning and would give them a horsepower advantage. Howard

You my friends have given a good over all review of the GASOLINE. and the Silverwing's performance.
The only thing I would say is stay away from the Ethanol products if you can

I agree with Cosmic, do not buy the cheapest gas. Buddies of mine buying cheap gas filled their van tank with a LOT of water. This would be tough on a Honda in the middle of central Arizona esp on a sunday.

Price of gas doesn't guarantee it being moisture free. That's a matter of the gas station operator properly draining and changing his tank filters.
Speed of burning of gasoline is a function of its specific gravity not octane. Higher octane fuels can have a higher specific gravity due to the additives that are present in the fuel to prevent detonation. It's also easier to ignite low octane fuel, the additives in high octane fuel are there to prevent the fuel from auto-igniting (ala diseling). If you have a lower compression engine the SW has 10.2:1 you get no advantage at all with high octane. My
C650GT does need at least mid range fuel with its 11.6:1 compression ratio. Advantage Silverwing.

At the 10.2: compression ratio of the SW you are within the compression ratio for 87 octane.
You can use higher octane but it won't improve performance other than lightening up one's wallet a bit.

From the Honda Silverwing 600 Owner's manual:

Your engine is designed to use any
unleaded gasoline that has a pump octane
number of 86 or higher. Gasoline pumps
at service stations normally display the
pump octane number.

We have always burned 87 or 88 octane in our Silver Wings and have no problems with it. Fuel mileage is usually around 50. Our Harley FLHTCU Electra Glide, however, is another matter. It has an 80 cube Evo with Screamin' Eagle Stage III heads, Andrews EV27 cam, and Vance & Hines pipes. The stock compression ratio was 8.5:1 and the heads raised it to 8:8:1. When we ran it on the dyno it would ping on regular and produced the most hp and torque (84.2 rear wheel bhp @ 5,050 rpm and 88.6 lb-ft torque @ 2,670) on 91 octane premium with no ethanol in it. On 87 octane regular with 10% ethanol it was down to 79.8 bhp and 85 lbs of torque.

We just got back from a road trip to North Carolina and Nova Scotia on the Glide riding two-up and fully packed for 10 days on the road. We kept track of mileage and fuel receipts for the whole trip. Some places we couldn't get 91 octane premium with no ethanol so had to fill up with 10% ethanol premium. On the fillups with ethanol gas our mileage averaged 50.2 mpg, when we could get real gas the big Glide gets 53.5 mpg.

Real world agrees with the dyno charts on our Electra Glide.

If you have an engine that requires the better grade of fuel, it does make a difference. The Silver Wing, however, is not one of those in my experience. The Silver Wing's engine and drivetrain is horribly inefficient compared to our 29 year old Harley, that develops over double the horsepower and torque, and hauls a curb weight of over 1,000 lbs down the road at the same fuel mileage as a Silver Wing at about 60% of the weight. Part of it is engine design. The Harley has a 4.25" stroke and only ticks over at 2,250 rpm @ 60 mph. But because of the long stroke it has stump pulling torque that will rip your arms off if you wack the throttle at 1,500 rpm. It produces more torque at idle than the Silver Wing's engine produces at peak. Because the pistons move so slow compared to the short-stroke, high-revving SWing engine, cylinder pressure builds very rapidly after ignition. This is because the total cylinder volume does not increase as fast with the slow-moving pistons, so it requires a fuel that burns slower to prevent excessive pressure buildup in the cylinder that would cause the remainder of the air-fuel charge to detonate.

The oversquare, high-revving engine designs that the Japanese manufacturers have always been fond of have such high piston speed that the fuel cannot burn fast enough before the piston reaches the bottom of its stroke and the exhaust valve(s) opens. So it ends up puking unburnt air-fuel charge out the exhaust and it's wasted (as HC emissions, which gets burned by the catalyst in the exhaust). Switching to a higher octane number (slower burning fuel) only exaggerates the problem, so fuel mileage will typically tend to be less with these type of engines if you use higher octane fuel than what is required.

The advantage with the oversquare designs the metrics like to use is that they can develop more hp in a smaller package, using rpm's to get it instead of torque. But torque is more important for everyday street riding than peak hp is because you rarely can use peak hp on the street without getting the undivided attention of law enforcement types. You can use peak torque all the time. I'll leave it to you to decide which design is more efficient. While you can't really compare our big Harley to the Silver Wing, you can compare it to a Goldwing - 15 mpg real world difference between the two bikes at the same weight, doing the same thing.

So my recommendation is to stick with the regular grade fuel in your Silver Wing - it is what it was designed and tuned to burn.