Better mileage at 87 octane compared to 91

[subaron]

I had switched to 91 octane earlier this year, thinking it would be cleaner and more efficient to burn and give a better mileage. But the opposite happened.

Over the winter I did two things to the bike.

1. Took the fairings off and went streetfighter
2. Did the throttle bodies sync using a home made manometer

When I started riding this year I noticed that with 91 octane I was getting a lower mileage of around 14 to 15km per liter.

I thought it was either wind drag since I had no fairings or I messed up the throttle sync.

While trying to search I came across some info regarding fuel, and reasons to burn 87 in fz6.

Figured it was easier to just fill in 87 octane over a few runs and see what mileage is achieve.

After 6 fill ups I can am consistently getting between 18 to 21 km a liter (depending on the style of riding).

This is a bit counter intuitive given the popular knowledge. Just thought I would share and see if anyone else has tried this experiment and achieved the same result.

 

[FIZZER6]

I have not tried this but I'm thinking about trying it now. 87 octane is more volatile (ignites a bit easier) so it would make sense that you may actually get more power per volume of fuel out of it which would allow more efficient fuel use.

The only reason I started using 93 octane is because my bike runs smoother on it, less engine vibration which probably has to do with the less volatile formula.

 

[mave2911]

Well, that is an interesting find. I run everything on 98RON, from my cars, lawn mower, whipper-snipper and of course, my bike.

I've always known 98 to burn a bit hotter and keep everything clean.

With the extra refining, it is also a cleaner fuel with more power.

Having said that, I am experiencing a decrease in fuel economy, so it would be good to see if this theory is correct.

I use fuelly, so all of my fills are available to view, so it'll be a nice transparent test with a large sample size.

I have to fill up tomorrow, so might do so with regular unleaded - for the first time...

Cheers,
Rick

 

[GTPAddict]

X2, I can see better fuel economy using lower octane fuel, but I can also see more engine problems (vibration, pre-detonation (spark knock), ect) by using lower octane fuel. These engines run 12.5:1 compression ratio, personally that's reason enough for me to stay with higher octane fuel. As far as I know there is no knock sensor on these bikes (at least not on my 06), so the PCM will not be able "hear" spark knock if it occurs and retard timing.

 

[yamihoe]

I have the same thing. My bike runs like complete crap on 91!
it was about the same as far as smoothness at mid-high rpms but at an idle it sounded aweful and my mpgs went to hell.
I only put the 91 in to go drag racing and it was a disaster, siphoned the tank dry and put 87 back in and I spanked a CBR

 

[ChevyFazer]

I wonder if running 87 with the iridiums would help? After looking at that thread about the iridiums and fuel economy I've been thinking of ideas to get a better fuel burn while keeping the iridiums.

 

[Downs]

The manual states to use 87 octane. It was designed with this in mind. Compression ratio isnt the only determining factor in what octane to use. There are many variables one of them being combustion chamber shape.

There's really no extra refining involved and just because it has a higher octane rating doesn't mean its higher quality fuel.

Infact most fuel comes from the same refineries if it's delivered to stations in the same areas. Where fuels differ (as far as brand) is their additive packages.

Higher octane fuel is simply harder to ignite which makes it more resistant to pre detonation.

Sent from my iPhone

 

[FIZZER6]

The manual states to use 87 octane. It was designed with this in mind. Compression ratio isnt the only determining factor in what octane to use. There are many variables one of them being combustion chamber shape.

There's really no extra refining involved and just because it has a higher octane rating doesn't mean its higher quality fuel.

Infact most fuel comes from the same refineries if it's delivered to stations in the same areas. Where fuels differ (as far as brand) is their additive packages.

Higher octane fuel is simply harder to ignite which makes it more resistant to pre detonation.

Sent from my iPhone

I agree for the most part, but "premium fuel" has a higher grade (usually more detergents) than the 87 octane version. My father is a chemical engineer for BP. The same fuel that goes to Exxon stations may very well come off the same tanker that goes to the Quickie Mart, the only difference is the respective additive packages blending before shipment to the stations.

I am going to try 89 octane on the next tank and then go to 87 on the following tank and log my mileage.

 

[mikw73]

I am going to try 89 octane on the next tank and then go to 87 on the following tank and log my mileage.

Great! Share your results! I seem to get 44-46 mpg on the 93-rated (U.S. octane rating system, whatever we use here.) and 46-48 mpg on the 87. Which makes little sense to me. Maybe I ride faster when I'm running the high-test? I don't think I do. I run 87 most of the time, but throw in 3-5 tanks in a row of 93 every few months in case there's any truth to the high octane gas being better at keeping the engine clean. I think it costs about $1.25 more per fill-up to do it.

 

[ChevyFazer]

I agree for the most part, but "premium fuel" has a higher grade (usually more detergents) than the 87 octane version. My father is a chemical engineer for BP. The same fuel that goes to Exxon stations may very well come off the same tanker that goes to the Quickie Mart, the only difference is the respective additive packages blending before shipment to the stations.

I am going to try 89 octane on the next tank and then go to 87 on the following tank and log my mileage.

I've always herd and been told that it takes a few tanks of premium to "get the benefits" so I wonder if the same would apply in reverse? Basically I wonder if it would would be better to run a few tanks of 89, like 3 or 4 to get a better idea, then the same for 87?

 

[Downs]

My father is a chemical engineer for BP. The same fuel that goes to Exxon stations may very well come off the same tanker that goes to the Quickie Mart, the only difference is the respective additive packages blending before shipment to the stations.

I stated as much in my 3rd paragraph.

If anything I think that techron (chevron and texaco) has been shown to actually live up to some of the hype they talk about it as far as keeping valves and whatnot cleaner.

The fact is the little octane numbers on the pump do not equal quality.



Sent from my iPhone

 

[lastlaugh]

There is a reason Yamaha tells you in the owner's manual to use 87! Always use the manufacturer's recommended fuel. My VW says 91 it gets 91, my Chevy says 87 I use 87. I used to be an active member at supramania.com when my Supra was running. I never ran anything higher than 87 in that because that is what Toyota recommends.

 

[FIZZER6]

I'm curious if the engine runs a bit hotter on 87 v. 93 octane.

 

[DownrangeFuture]

I've always herd and been told that it takes a few tanks of premium to "get the benefits" so I wonder if the same would apply in reverse? Basically I wonder if it would would be better to run a few tanks of 89, like 3 or 4 to get a better idea, then the same for 87?

When I first got my bike I only used the highest octane gas at premium stations. I mean, my mom's mustang needed high octane gas, why not my higher revving zoom machine? And I would only do the best for my baby. I ran that way for about 6 months and 4000 miles or so. I got about 41-44mpg consistently. At about 150 a tank, that's far more than a "few tanks".

After I actually read the manual and I switched to 87, by the second tank I started getting over 50mpg quite consistently. Also, a few members on here have found that our cooler running engines don't play well with the iridium plugs.

Now, my monster runs on 91 as per the manual (that means 93 out here), so that's what I used, and I got 52mpg on my first tank. Take it for what it's worth.

 

[iSteve]

I believe yamaha recommends 87 or higher in case of detonation. I use to use 91, this year I gave 87 a try and found the bike got buzzy like lawnmower. I went back to 91. Don't notice any mpg difference but then again I don't really care a dollar a week won't kill me.

 

[VEGASRIDER]

I guess I've saved a lot of money then by using regular for the past 78,000 mies. Not only did I save money per gallon, I increased my fuel mileage.

It may not be much, but eventually it adds up.

 

[ChevyFazer]

When I first got my bike I only used the highest octane gas at premium stations. I mean, my mom's mustang needed high octane gas, why not my higher revving zoom machine? And I would only do the best for my baby. I ran that way for about 6 months and 4000 miles or so. I got about 41-44mpg consistently. At about 150 a tank, that's far more than a "few tanks".

After I actually read the manual and I switched to 87, by the second tank I started getting over 50mpg quite consistently. Also, a few members on here have found that our cooler running engines don't play well with the iridium plugs.

Now, my monster runs on 91 as per the manual (that means 93 out here), so that's what I used, and I got 52mpg on my first tank. Take it for what it's worth.

I could honestly care less about mpg on my bike, Ive been used to getting between 10-15mpg on every car/truck I've owned so id be happy with 30 tbh. If i want good mileage ill ride my klr. I did run on 87 before i put the iridiums in for about 1000 miles and I didn't notice any difference in mileage, but it felt like a diesel at idle and under load. 87 might be best for a STOCK fz6 but I left stock behind about 20,000 miles ago lol.

And for The post you quoted, I was suggesting for the member instead of only running one tank of 89 through his bike and recording his mpg to run a few tanks through. For one to make sure all of the higher octane would be flushed out, and also to have a better average. Then to do the same on 87.

 

[mave2911]

I don't even think I can GET 87RON - all of the servos I frequent start at 91 (Unleaded), 95 (Premium) or the stuff I have have been using, 98 (Vortex (Caltex), Ultimate (BP))

It's been p!ssing down here, so haven't ridden for a few days, but hopefully it'll be dry for me to ride when I'm back on shift Sunday)

I'll fill up with 91, and use 3 tanks in about 2 weeks, so it will be a nice quick result.

Interesting to see if the 91 behaves better with the Iridiums (maybe the less spark generated with the lower efficiency Iridiums, and using the 98RON, the less volatile fuel, is a mix of worst case scenario?)

I'll change one thing at a time - try with 91 for a few weeks, then change the plugs back to NGK copper and see if I get further improvement. (try to minimise other variables)

Cheers,
Rick

 

[Tagger]

in belgium it's 95 or 98 ... there's not even a thing like 87

 

[bob808]

Yes, in Romania the same, 95 or 98. Maybe we can dilute it with something