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Discussion Starter #1
I generally follow the OEM owner and service manual recommendations, but noticed a lot of 1500 owners regularly use 87 octane which is below the 90 minimum for the 1500 engine.

I tried 87 and the engine runs fine even in hot weather - no pinging that I can hear. In fact, I notice a little better gas mileage using 87 and I think it may even have a little more power, but that could be just my imagination.

But, I'm still a little concerned since the manual states severe engine damage can occur using a lower octane. Could there be any long term consequences using the lower octane?
 

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Japanese and Europeans use the RON (Research Octane Number) to come up with their octane rating. In the states, we use the RON and the Motor Octane Number, or MON, add the two and divide by two. Thus, a 91 RON will be an 87 RON+MON/2. Look at the gas pump and you'll see either RON+MON/2 in parentheses, or AKI, the Anti-Knock Index, which is the same thing.

I looked in my owner's manual and it said 91 minimum octane RON. Which means 87 here is just fine.

I use to run premium in the bike, and it ran a bit sluggish and got lower mileage. I didn't understand all this octane stuff at first, and like most consumers, assumed that higher octane gas was "the good stuff", had more power and so on because of oil company marketing. But in reality, octane rating is simply the point at which fuel ignites under pressure and how quickly it burns. For high compression engines, like racing engines or some higher end passenger cars, a lower octane could result in the fuel pre-igniting under compression, causing pre-detonation, which can destroy an engine. Thus, higher octane was introduced to retard detonation. That's all it does. Otherwise, the gas is pretty much the same. But if your engine is a lower compression engine, the premium may not burn as quickly and can (but not always) cause some carbon buildup and reduce mileage.

Best to follow the manual. If your manual says 91 octane RON best use it. If not, you're wasting money for no added benefit.

FWIW, some guys swear by premium fuel with no ethanol in it, but ethanol serves basically the same function as octane. That is, it burns at a lower temperature and is slower to ignite under compression than straight gasoline, and does not burn as quickly. But in my bike, 87 octane with ethanol still seems to be more efficient than premium 91.
 
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Pat's got it. There doesn't seem to be a rhyme or reason, but some Vulcan models list RON, and some R+M/2. My 900 listed 91RON, which is equivalent to 87 R+M/2. The Vaquero listen 91 R+M/2 as minimum!

Run at least what the manufacturer recommends. Running higher won't hurt anything but also won't provide any benefit unless engine timing is manipulated to take advantage of it.

Also; because this always comes up in Octane threads; compression is not the only metric anymore. Both the VN900 and VN1700 platforms have identical compression ratios but the VN1700 requires 91 R+M/2 and the 900 87. Likely the 1700 needs the higher octane due to higher combustion temps that can occur at some points, such as aggressive riding or riding in traffic (Where the engine gets warm). My car has a 12.5:1 compression ratio and thanks to variable valve timing, anti-knock sensors that electronically adjust ignition and other such technologies it can run just fine all day lone on 87. Because the engine adjusts itself, on a Dyno, there are significant gains running a higher octane fuel. Some might look at those results as evidence that more octane = more power. But the reality is, it's the engine, not the octane. On our bikes, there won't be meaningful gains unless we adjust timing. On cars that do adjust timing automatically (most modern cars), higher octane fuel will provide a boost in power.

Octane is a resistance to detonation. Period. Not cleaner, not more powerful, not anything else. The aforementioned performance gains come because cars can advance timing and take advantage of longer burns without detonation. Timing being equal, power will be equal.

As for Ethanol, it's not evil. It won't corrode your parts. E10 is not the same as E85, which is harmful. If you remember back in chemistry class, you remember that things in different quantities in solution have different properties. Sodium and Chlorine are both toxic, caustic, and will kill you. Together they form sodium chloride which you need to live, and probably put too much of all over your food! (Table salt). But mixed in a slightly different way and you get some of the gasses that were used to kill troops in WWI. E10 won't harm your engine. It will absorb more water than straight gas, and does have less potential energy than straight gas; so it's not without it's caveats. But it won't hurt anything. All fuel, E10 or otherwise, should be stored properly when not used for any extended length of time (whether stored in a can or stored in a bike over the winter).
 

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Discussion Starter #4
Japanese and Europeans use the RON (Research Octane Number) to come up with their octane rating. In the states, we use the RON and the Motor Octane Number, or MON, add the two and divide by two. Thus, a 91 RON will be an 87 RON+MON/2. Look at the gas pump and you'll see either RON+MON/2 in parentheses, or AKI, the Anti-Knock Index, which is the same thing.

I looked in my owner's manual and it said 91 minimum octane RON. Which means 87 here is just fine.
Thank you PatC.

My 1500 is an 02 Drifter and no paper owner's manual was available. The generic online PDF Owner's Manual for 1500 Drifters states the AKI, or RON+MON/2 minimum rating is 90. It lists the RON minimum rating is 95.

That's my concern and reason for confusion. Apparently some 1500 models and years have different minimum octane ratings. Yours list a lower minimum. I was under the impression most 1500 engines and years had the same compression ratio of 9.0:1. I guess not.
 

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Thank you PatC.

My 1500 is an 02 Drifter and no paper owner's manual was available. The generic online PDF Owner's Manual for 1500 Drifters states the AKI, or RON+MON/2 minimum rating is 90. It lists the RON minimum rating is 95.

That's my concern and reason for confusion. Apparently some 1500 models and years have different minimum octane ratings. Yours list a lower minimum. I was under the impression most 1500 engines and years had the same compression ratio of 9.0:1. I guess not.
Again, compression is NOT the only metric. It was in 1965 when all of the engines were the same 2 valve pushrod V8's and the only difference was displacement and compression, but today that's not the case. Ignition timing, valve timing, etc. etc. all affect the need for higher octane. Both the VN900 and VN1700 have the same compression ratio but need different octane ratings; and there are cars (like mine) with a 12.5:1 compression ratio that will adjust and run on 87 just fine.
 

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Discussion Starter #6
Pat's got it. There doesn't seem to be a rhyme or reason, but some Vulcan models list RON, and some R+M/2. My 900 listed 91RON, which is equivalent to 87 R+M/2. The Vaquero listen 91 R+M/2 as minimum!
Thanks Romans. I've read quite a bit on the subject here on the forum, and I'd like to think all 1500s are the same, but apparently not.

On the ethanol, E10 is pretty much everywhere now and I understand E15 was to be, and may still be phased in at some point. (I think E15 and E85 are the same mixture) My 08 truck is "Flex fuel" approved for up to E15, but my outboard motor sure isn't.

I still don't get any "pinging" using 87 in the 1500 Drifter, but maybe the pipes are so loud I couldn't hear it anyway.
 

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Thanks Romans. I've read quite a bit on the subject here on the forum, and I'd like to think all 1500s are the same, but apparently not.

On the ethanol, E10 is pretty much everywhere now and I understand E15 was to be, and may still be phased in at some point. (I think E15 and E85 are the same mixture) My 08 truck is "Flex fuel" approved for up to E15, but my outboard motor sure isn't.

I still don't get any "pinging" using 87 in the 1500 Drifter, but maybe the pipes are so loud I couldn't hear it anyway.
Usually Flex Fuel Vehicles are approved for up to E85. E10 is the maximum typical engines can handle. That's 10% ethanol, (E15 is 15%, E85 is 85%). 10% ethanol won't harm a gas engine; but when you start getting to 15% of above it needs the right kind of materials to prevent damage. Ethanol still inhibits performance. Folks with E85 vehicles rarely use E85 because the severely reduced fuel economy significantly outweighs the lower cost of the fuel. Though it is popular in some custom setups; it's cool burning and extremely high octane rating (E85 varies but is generally around 100~105R+M/2), it's popular in heavily turbocharged setups and the like.

Pinging can happen without being audible which is why I suggest you never go below the manufacturers minimum. A misconception is that engines will ping a lot, under all conditions, with too low of an anti knock rating. But that's not the case. Often the manufacturers recommendation is after testing and discovering detonation under heavy loads at high temperatures, for example. But any pinging can cause damage, which is why using the minimum suggested by the manufacturer is advised.
 

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Thank you PatC.

My 1500 is an 02 Drifter and no paper owner's manual was available. The generic online PDF Owner's Manual for 1500 Drifters states the AKI, or RON+MON/2 minimum rating is 90. It lists the RON minimum rating is 95.

That's my concern and reason for confusion. Apparently some 1500 models and years have different minimum octane ratings. Yours list a lower minimum. I was under the impression most 1500 engines and years had the same compression ratio of 9.0:1. I guess not.
Yes. different models have different requirements, which is why one need always read the manual. However, like I said earlier, added ethanol serves essentially (not completely, but probably close enough in your case) the same function as higher octane, which is why 87 isn't causing pinging in your bike. (you would likely not only hear it, you'd feel it and it would run very hot). But if you're concerned, just run 91 premium in it and it'll be fine. :smile2:
 

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All very good info. Thanks so much. Based on what you've said I started buying 87 (with ethanol). After 3 tanks I am now getting 2 mph better. I also noted it seemed to be running better. No knocks. Yesterday, I opened her up and she runs 112 now. On 92 or 93 she topped out at 105. The only confounders is an oil change and new air filter. As the old one wasn't visibly dirty, I don't think the filter plays. Wind and elevation and incline aren't variables either..., very intriguing.
 

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Yes. different models have different requirements, which is why one need always read the manual. However, like I said earlier, added ethanol serves essentially (not completely, but probably close enough in your case) the same function as higher octane, which is why 87 isn't causing pinging in your bike. (you would likely not only hear it, you'd feel it and it would run very hot). But if you're concerned, just run 91 premium in it and it'll be fine. :smile2:
That's actually not quite the case. 87 E10 has the same anti-knock capabilities as 87 E0. Ethanol has great anti-knock properties, you're right. As a result, the fuel manufacturers use less of the anti-knock additives they would normally use, because of the ethanol. I'm using made up numbers here because I don't know the specific formulas, but, it'd be like starting with 83 octane fuel, mixing in 10% ethanol, and ending up with 87. E85's octane rating is well over 100.

Pinging isn't always audible. But it can still do damage. I wouldn't run less than what the manual says (while checking for that 'translation error' or RON/R+M/2), but that's just me. You won't hurt anything with 'too much octane' other than just wasting a little money.

And, at the end of the day, I just can't find anyone on this forum reporting a hole in their piston. Though you can find such catastrophic failures on other forums where folks have cars requiring high octane fuel, and run regular for an extended period!
 

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That's actually not quite the case. 87 E10 has the same anti-knock capabilities as 87 E0. Ethanol has great anti-knock properties, you're right. As a result, the fuel manufacturers use less of the anti-knock additives they would normally use, because of the ethanol. I'm using made up numbers here because I don't know the specific formulas, but, it'd be like starting with 83 octane fuel, mixing in 10% ethanol, and ending up with 87. E85's octane rating is well over 100.

Pinging isn't always audible. But it can still do damage. I wouldn't run less than what the manual says (while checking for that 'translation error' or RON/R+M/2), but that's just me. You won't hurt anything with 'too much octane' other than just wasting a little money.

And, at the end of the day, I just can't find anyone on this forum reporting a hole in their piston. Though you can find such catastrophic failures on other forums where folks have cars requiring high octane fuel, and run regular for an extended period!
Yes, it could be wrong. I was paraphrasing a fuel research guy from Shell Oil. The point is, ethanol burns slightly slower and not as hot as gasoline, slightly reducing the flash point of the gasoline, which is essentially what increased octane does as well. Put simply, anyway. There's more to it than that, of course, but that's the layman's version. Ethanol is no substitute for higher octane. What complicates it is the other additives, brand, and what state one resides in, as each has a different fuel formula requirement.

We just bought a new Subaru Forester cage. If you want to read something confusing, the fuel requirements in the owner's manual is like reading a riddle. It recommends premium, but will run fine on regular, but not for long, and maybe half and half will work, but premium isn't a requirement, just recommended, but you should run it. Whew!:confused::surprise:
 

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So, here's a question along those lines. Kawasaki recommends 91 octane for my 1500, but in my neck of the woods the choices are 89 or 93, 91 is not available. What you guys recommend, go up or down?

Thanks
 

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So, here's a question along those lines. Kawasaki recommends 91 octane for my 1500, but in my neck of the woods the choices are 89 or 93, 91 is not available. What you guys recommend, go up or down?

Thanks
Octane ratings are a minimum. So go up, not down. Though check your manual to see if it says "91RON", because if it does, that's equivalent to the 87 R+M/2 you have on your pumps. So you'd be safe to go with that.

Otherwise, generally speaking, use at least what the manufacturer recommends and no lower. Plenty go lower without problems, if you want to, go for it. But that's, at least, what the manufacturer is saying when they give you a minimum recommendation.

My bike asks for 91 R+M/2, and I frequently run 93. Often times, actually, 91 is made by mixing 93 octane fuel with 89 or 87. It's not uncommon for gas stations to have two tanks; 87 and 93, and mix various ratios to produce 87, 89, 91. Whereas the other station down the road might have the same 93, pumped straight, for the same price. (This is according to a family friend who is a general manager for a gas station chain. In her case, they get 87 and 93 delivered, sell 87 and 93, and have a mixing pump that makes 91 and 89.)
 

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So, here's a question along those lines. Kawasaki recommends 91 octane for my 1500, but in my neck of the woods the choices are 89 or 93, 91 is not available. What you guys recommend, go up or down?

Thanks
What Romans said. Japanese and Europeans calculate octane differently than we do in the US and Canada. They use the Research Octane Number (RON) only. We use the RON + the Motor Octane Number (MON) and average the two. Thus, 91 in Japan/Europe is the equivalent of 87 in the US. I've run 87 in mine for years with no ill effects whatsoever.


Read your owner's manual to see if it says 91 RON (like mine does for my '04 Classic) or if it says 91 RON+MON/2, like some of the newer 1700s do. It may say AKI, which means Anti-Knock Index, which is the same as RON+mon/2.
 

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Wait. Wait, Pat. Now I'm confused. I thought you and Romans were saying that if it said 91RON only it was equivalent to 87, but if it said 91 R+M/2 to go up to 93. Can you clarify your last post?

Thanks
 

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Wait. Wait, Pat. Now I'm confused. I thought you and Romans were saying that if it said 91RON only it was equivalent to 87, but if it said 91 R+M/2 to go up to 93. Can you clarify your last post?

Thanks
No, it's the opposite.

91 RON in Europe and Japan is equal to 87 RON+MON/2 in the US and Canada.

Here's a handy chart:

Octane rating conversions - PencilGeek's BMW Blog
 

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In the United States, the anti knock rating is expressed as "Ron + Mon / 2". Also "AKI" or anti knock index; all the same thing.

In Japan and other countries, they use simply RON.

So if your manual says 91RON, that's equivalent to 87 R+M/2. So you can use as low as 87 at the pump.

If it says 91AKI or 91 R+M/2, then that means you need to use at least 91 at the pump.
 

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Ok, sorry guys. Romans and PatC seem to be contradicting each other. Maybe I'm adding to the confusion, so let's start over again...forget Japan and Europe.

I live in Ohio, USA. My 2002 , 1500FI says 91 R+M/2. My choices at the pump are 87, 89, or 93. My question is 89, or 93?

Thanks
 
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