The Best Fuel

[ManWithAVision]

What octane rating do you use? Does a higher rating make a difference in the performance level and maintenance of a Second Gen or late model RSTD motor?

[Guest divey]

What octane rating do you use? Does a higher rating make a difference in the performance level and maintenance of a Second Gen or late model RSTD motor?

 

I don't know what the rating is but I burn regular gas without any performance problems. Once however I filled up at a Mohawk station which sells an ethanol blended fuel, supposedly more environmentally friendly. It burned okay but the engine definately lacked oomph and did not run as smoothly as before. Once I got rid of that tank full and filled up with the usual Shell/PetroCan/Esso fuel, it ran fine. May have been a bad tank of fuel but I won't risk filling up again at Mohawk or Husky if I can help it.

 

Doug

[ManWithAVision]

I usually get my gas at the local Shell station near my home. They have three blends available with octane ratings of 87, 89, and 91. I recently noticed that the two lower ratings (87 & 89) contain ethanol, but the most expensive one with a rating of 91 specifies that it contains no ethanol.

 

Since I got my bike last fall I have been using the middle blend. Tonight I spent a whopping $13.64 and splurged on the primo blend. Will have to see if it makes any noticeable difference after a couple of tankfuls.

[RandyR]

87 octane regular. Most of the regular gas in this area contains 10% ethanol, even the name brands. I haven't noticed a problem so far.

[similost]

I'm not sure what the compression ratio is on these bikes, but premium blend is meant for higher compression engines to help prevent pre-detonation, or spark knock. If you aren't getitng a spark knock from lower octain rated fuels, you really don't need premium.

 

A higher octain fuel is meant to burn at higher temps. If you use a higher octain fuel in a lower compression engine you don't get as full a burn, and carbon will build up faster in the combustion chamber.

 

I won't use premium fuel in anything lower than a 10:1 compression engine. If you are using it in anything lower you are just spending money you don't need to, not getting as complete a burn, and building up carbon in your engine.

[bryan52577]

Engine Type V4

Cylinders 4

Engine Stroke 4-Stroke

Horsepower (bhp/kW) 98 / 73.1 Horsepower RPM 6000

Torque (Ft Lbs/Nm) 89 / 120.6

Torque RPM 4750

Cooling Liquid

Valves 16

Valves Per Cylinder 4

Valve Configuration DOHC

Bore (mm/in) 79 / 3.11

Stroke (mm/in) 66 / 2.6

Displacement (cc/ci) 1294 / 79

Compression Ratio 10:1

Starter Electric

Battery Amp Hour 18

Fuel Requirements Regular

Ram Air Induction No

Fuel Type Gas

Carburetion Brand Mikuni

Fuel Injector No

Carburetor Yes

Number Of Carburetors 4

Carburetor Size (mm) 32

Carburetion Type Carburetor

 

Looks like it is 10:1 compression

 

Bryan

[jfoster]

That's what I like about the Royal Stars...Regular Fuel. I've always pondered if you buy gas at a station that feeds all three grades through one hose. How much of the regular to do you get before the super gets to the tank. I've ran both and honestly couldn't tell any difference (with pumps that each grade has its on hose).

[LilBeaver]

Right on. I have noticed that the tag on the bike says to use a minimum of 91 octane **86 Octane as read off the pump in US&CAN [Thanks Goose -- see post below for further explanation]** (on the tag with the tire pressures, etc. on my 01 RSV i believe it is on the lid of my left side (sitting on the bike) saddle bag - But I do not recall exactly at the moment. The manufacture suggested fuel octane rating is based off of sea level operation and the ambient air being at (essentially) STP.

 

An additional thing to note is that at higher altitudes you do not need as high of an octane rating, as the air is less dense and on the compression stroke there is less air in the cylinder which requires a flash point of the fuel to be lower - thusly one would need a lower octane rating.

 

Here in Lubbock Texas, we sit at a lovely 3,000 ft above sea level and 'regular' is 86. In Denver, ~5280 ft above sea level, I believe the 'regular' is 85 - not to be confused with e85 and vehicles "designed" to run off of that garbage.

 

At sea level, (if I recall correctly) the suggested Octane rating and compression ratios go something like:

~7:1 through 10.5:1 - use 87

10.5:1 through 12:1 - use 89

12:1 through ~14:1 - use 91 (Typically you cannot get above 13:1 without some sort of forced induction system or supercharging system - which is why high performance cars typically say they need premium and why I have no idea why the tag on these bikes would say to use 91 - as it is a waste of money and will cause excess build up of the non-completely burnt fuel as well as deposits on the valves and plugs)

 

Summary: Higher octane rating increases the tolerance for the fuel to 'pre-ignite' as similost said

 

If anyone wants more details, say so and I can fill you in... But I think this is the basic info so I'll stop rambling...

 

A higher octain fuel is meant to burn at higher temps. If you use a higher octain fuel in a lower compression engine you don't get as full a burn, and carbon will build up faster in the combustion chamber.

Edited April 29, 2009 by LilBeaver
I had written information that was misleading, sorry folks

[V7Goose]

Right on. I have noticed that the tag on the bike says to use a minimum of 91 octane (on the tag with the tire pressures, etc. ...

This statement is almost correct, and VERY misleading.

 

The sticker on the RSV specifically states 91 RON octane (note the "RON" is missing in the quote). Unfortunately this is NOT the same as the octane number you see on the pump in the USA or Canada. The RSV is designed to run on regular unleaded fuel of 86 PON octane or higher, as stated in the owner's manual.

 

Explanation:

Octane is measured with two different methods (Research Octane Number (RON) and Motor Octane Number (MON)) and reported as either RON, MON, or an average of the two, called Pump Octane Number (PON), or (R+M)/2. In the USA, federal law requires all pumps to bear the average or PON octane number.

 

This engine is designed for regular gas. Buying anything higher than 86 PON octane is a complete waste of money, but won't hurt a thing.

Goose

[WAC1972]

I usually run high 93 octane in my 96 RSTC and it runs well and gets around 40 to 41 MPG. I will on occasion run regular 87 octane and my bike get about 35 MPG and seems sluggish. I like the higher octane but I do get some popping on deceleration and my pipes do show signs of carbon deposits while using the higher octane. I am interested in others opinions on which to stay with.

[V7Goose]

I know there are people who will insist their experiences are different, and I have no desire to try and disabuse them of their beliefs, but the fact is many studies have shown over and over again that higher octane does NOT produce more power or better gas mileage. I won't take the time to document those studies here, but they are quite easy to find.

 

Higher octane does absolutely nothing other than allow a fuel to resist detonation in a spark-ignited engine (commonly referred to a "knocking") . It is important to use a fuel with high enough octane to prevent knocking in a specific engine, but anything above that provides NO additional value to the engine.

Goose

[dragerman]

I know there are people who will insist their experiences are different, and I have no desire to try and disabuse them of their beliefs, but the fact is many studies have shown over and over again that higher octane does NOT produce more power or better gas mileage. I won't take the time to document those studies here, but they are quite easy to find.

 

Higher octane does absolutely nothing other than allow a fuel to resist detonation in a spark-ignited engine (commonly referred to a "knocking") . It is important to use a fuel with high enough octane to prevent knocking in a specific engine, but anything above that provides NO additional value to the engine.

Goose

[LilBeaver]

Good call Goose -- I forgot about that distinction when I wrote what I did above ... Quite embarrassing. Incidentally, I've used nothing but regular in mine without thinking twice about it.

 

This statement is almost correct, and VERY misleading.

 

The sticker on the RSV specifically states 91 RON octane (note the "RON" is missing in the quote). Unfortunately this is NOT the same as the octane number you see on the pump in the USA or Canada. The RSV is designed to run on regular unleaded fuel of 86 PON octane or higher, as stated in the owner's manual.

...

[boatwg]

I really can't tell a difference in 87 or 93 octane. I usually use 89. I find some stations seem to have better gas than others and not sure why. I have heard timing could be an issue.. Right after the stations get a fillup it could stur up sediments that could cause poor performance.

 

On Ethanol issue, I have heard that it is an alcohol so it has a tendancy to dry the rubber lines and gaskets over time. Is this true? It seems most stations are going to the 10% blend. Does this mean shorter engine life?

[V7Goose]

I really can't tell a difference in 87 or 93 octane. I usually use 89. I find some stations seem to have better gas than others and not sure why. I have heard timing could be an issue.. Right after the stations get a fillup it could stur up sediments that could cause poor performance.

 

On Ethanol issue, I have heard that it is an alcohol so it has a tendancy to dry the rubber lines and gaskets over time. Is this true? It seems most stations are going to the 10% blend. Does this mean shorter engine life?

Alcohol can damage components that pure gas does not (primarily rubber), but as long as it is no higher than 10% ethanol, it is unlikely that you will ever have a problem other than lower fuel mileage. Methanol is much harder on fuel systems - some stations used to sell 5% methanol gas, but I haven't seen that in years. Yamahaha specifically says not to use methanol.

 

Since alcohol has less energy per volume than gasoline, it WILL reduce your miles per gallon and possibly even make a detectable difference in how much power you feel in the engine. I hate the stuff, but often you don't have a choice.

Goose

[ManWithAVision]

Many thanks folks for all the input. Looks like I'll be using the cheap stuff from now on as long as there is no pinging or knocking.

[Tatonka]

I'm late as usual to put a word in. The previous owner of my 98 RSTC which I bought last year with 10,146 miles on it, said he always used premium fuel and it ran fine.

 

I then bought the owners manual from Yamaha Pubs and found it said regular, at least 86 or higher octane. It also said ethanol up to 10% was ok but recommends not to use methanol because of fuel system damage.

 

I started using regular and my gasoline mileage increased somewhat and the engine ran smoother. While on the Legacy Run last year, we got mainly premium gas at the stops and I started having performance problems and popping. I started tanking regular on my credit card during the Run and I had no more problems.

 

After the Run I did another 7,716 miles on my own, mainly west coast and midwest. I only noticed some problems at some gas stations mainly in Kansas and Oklahoma and one in Colorado where the regular had my bike wheezing and hacking like an old man. Went back to the brand name stations I know and it cleared up. I changed spark plugs in Oklahoma and it seemed to go better with regular gas from well known chains after that.

 

I guess bikes are like people. My 82 XV920 runs well on the middle blend and the premium seems to be ok too. It doesn't like regular, so I listen to it. It ran well in the rain here in DC today until I found that I forgot to close the choke.

 

Ride hard and ride safe and hope to see some of you on the American Legion Legacy Run in August. After that, I plan to ride through those states missing on my map.

[CrazyHorse]

If I could find a gas with no ethenol I would use it no matter the octane. Higher octane has done nothing for me but pure gas can.

[Derrest]

I use 86 octane down here in Dallas. We are going to Winterpark CO in early August. Their Octane is 85 for regular and 87 for mid grade. So Since it doesn't require as much oxygen to ignite, I am assuming it is OK to burn Regular (85 Octane) up there. Is that correct?

[Leland]

Yes, burn the 85.

[MiCarl]

Alcohol can damage components that pure gas does not (primarily rubber), but as long as it is no higher than 10% ethanol, it is unlikely that you will ever have a problem other than lower fuel mileage.

 

I heard an argument on the radio a few weeks ago between someone from the marine industry and someone in one of the government agencies. Apparently there are moves afoot here in the U.S. to require 15% ethanol in the non-aviation gasoline.

 

Basically the marine guy was complaining that the fuel had only been tested in a few brand new cars and not in any older vehicles or marine engines. The gov't position was "We think it'll be fine. Yeah, we ruined all the fiberglass tanks with the 10% but nobody uses them anymore so 15% will be ok."

 

I suspect we can count on a 15% ethanol blend in the not too distant future.

[LLonearth]

I won't use premium fuel in anything lower than a 10:1 compression engine. If you are using it in anything lower you are just spending money you don't need to, not getting as complete a burn, and building up carbon in your engine.

 

Where does leave us poor first gen cousins with our 10.5:1?

[McBrush]

I've run nothing but regular (87 in OH) in mine and have had no performance issues. When I first bought my 1100 Virago I ran 89 (mid-grade) and had a lot of 'popping' during decel, and since I switched to regular it's been great. For me, running the recommended grade works. I'm a heavy load by myself, but even with my packed bags I average well over 40 MPG on my trips with the RSV running regular fuel.

[jfoster]

My 06 RSTD definitely does not like the 10% ethanol...not only does it cost the same as gas with no ethanol but, I got on average of 5 mpg less fuel economy. I personally hope they all don't go to it or atleast give us the option to purchase high octane instead.

[GaryZ]

An Ethanol blend seems to be ok in most engines when it is used quickly. It seems that Ethanol turns bad much faster than 100% gas. It is said that it also separates in your tank and sinks to the bottom. My experience has been very bad with Ethanol in my bikes that do not get ridden regularly. Gummed up carbs.

 

I now use only 100% gas and still pour in a little SeaFoam as a stabilizer.