| Author | Message | ||
     Jlnance |
I normally run 93 octane gas in the Uly. It's never had a pinging problem, I just do. Well I decided to see how it did with 89 octane Saturday, and I didn't notice any difference. Until I filled it back up. It's just one datapoint, but I got really good gas mileage off that tank of 89. Which lead me to wonder, what are the chances that 93 octane is the same stuff as 89, with it's octane raised by adding Ethanol? | ||
| Indy_bueller |
I suppose it's possible, but you would have to sample and test the gas to know for sure. | ||
| Just_ziptab |
The recommended fuel octane for your vehicle is the best overall. Around here, 87 and 91/93 octane is straight gas. 89 octane is 10% ethanol and the 10% ethanol will always yield poorer mileage. YMMV. | ||
| Hughlysses |
Outside of ethanol content, all other things being equal, the lower the fuel octane rating the higher the BTU/gallon content. It's a relatively small difference, but it's a fact of the distillation process. Gasoline is made up of a myriad of hydrocarbon compounds. The compounds that raise the octane are the lightest fractions that are distilled from crude oil. (They used to get around this by adding tetraethyl lead to raise the octane.) It follows that the heavier the compound, the higher the BTU content. Hence diesel has more BTU's/gallon than kerosene, kerosene has more BTU's/gallon than regular gas, and regular gas has more BTU's/gallon than premium gas. This explains how you could get slightly better mileage off of 89 octane fuel vs. 93 octane fuel. The other part of the equation is a high compression engine is more efficient than a low compression engine, so the lower BTU content of the fuel is somewhat offset by the higher efficiency of the high compression engine that the premium fuel allows. Higher octane also allows you to run more spark advance. You might be able to advance the timing slightly on your Uly using premium fuel and find that it gets the same mileage (and possibly slightly improved performance) compared to 89 octane fuel. Of course the manufacturer's recommended octane rating is probably a little conservative, and the weather's not that hot right now, so it's not that surprising you can run on 89 octane without problems. You're probably just coming much closer to the threshold of ping than you were with 93 octane gas. When it's 100 degrees F outside it may not do so well. | ||
| Lemonchili_x1 |
What fuels are commonly available in the U.S.? Here normal unleaded is 91RON, premium is 95RON, and most brands have a high octane 98RON fuel as well. Ethanol blends are becoming more available, but are limited to 10% ethanol, I think they are still 91 octane. | ||
| Ratbuell |
Around here (central East Coast US) we've got 87, 89, and 91 as common. 93 at some of the name-brand stations, but 91 works just fine for my bikes. Anything higher than 93, you have to go to a speed shop or dragstrip. | ||
| Jaimec |
FYI: If I remember correctly, PURE gasoline has an octane rating of 66 (Hence, "Philips 66" for you old-timers). Additives are used to raise the octane. The number on the pump is supposedly the MINIMUM octane rating for the gas in the below ground storage tank. That means if it is labeled "89 octane" it could very well be HIGHER than that. If your engine requires 90 octane (pump), then you could very well get away with 89 octane. More information available here: http://www.ibmwr.org/otech/octane.html | ||
| Arcticktm |
Big difference to remember: USA uses (R+M)/2 method for pump octane ratings. Europe uses the R number (RON=Research Octane Number) only. The R number is from the "Research" test, and is a higher value for the same fuel as the M "Mechanical" test, which is a value from a test engine. The USA take these 2 results and averages them. Don't take me to exact, but I recall that 95RON is about the same as typical premium rating of 91-92 (R+M)/2 or so in the US. | ||
| Just_ziptab |
With 10% ethanol(89 octane), I get 20 mpg in the truck. With straight 87 octane I get 23 mpg. The 87 octane costs 10 cents more a gallon, but goes farther by the tune of TWO CENTS a mile. It is totally stupid to use 10% ethanol. Yet the subsidies and collusion make that 10 cents look pretty good..it's all a ruse with ethanol.......you're only shitting yourself......... period! | ||
| Ryker77 |
Which lead me to wonder, what are the chances that 93 octane is the same stuff as 89, with it's octane raised by adding Ethanol? Octane is raised also by xylene and other _____lenes. The fuel started out the same and is mixed up to the desired octane. Same tank, same tanker, same fuel lines all can effect true octane. Ethanal just sucks and is stupid. That said I run 1 gallon of alchol per tank due to my 120hp engine. | ||
| Just_ziptab |
Makes you wonder why anybody would run E85 if you didn't have to. And you thought the internet was where you get scammed. |
