what's the diff between 87,89.93 gas octan? when all three have 10% ethnol

Discussion in 'Lawn Mowing' started by Green Quality, Apr 27, 2011.

  1. Green Quality

    Green Quality LawnSite Member
    Posts: 176

    I have always though that higher grades of gas like 89 or 93 did not have ethnol in it. but to find out that they do. so than whats with the higher price? if they add that carp to89 or 93 it should be cheaper right ?
     
  2. topsites

    topsites LawnSite Fanatic
    Posts: 21,654

    These numbers refer to the octane rating, which is a measure for the anti-knocking properties of gasoline.

    Octane rating
    From Wikipedia, the free encyclopedia
    A US gas station pump offering five different (R+M)/2 octane ratings

    The octane number of a fuel is measured in a test engine, and is defined by comparison with the mixture of 2,2,4-trimethylpentane (iso-octane) and heptane which would have the same anti-knocking capacity as the fuel under test: the percentage, by volume, of 2,2,4-trimethylpentane in that mixture is the octane number of the fuel. For example, petrol with the same knocking characteristics as a mixture of 90% iso-octane and 10% heptane would have an octane rating of 90.[1] This does not mean that the petrol contains just iso-octane and heptane in these proportions, but that it has the same detonation resistance properties. Because some fuels are more knock-resistant than iso-octane, the definition has been extended to allow for octane numbers higher than 100.

    Octane rating does not relate to the energy content of the fuel (see heating value). It is only a measure of the fuel's tendency to burn in a controlled manner, rather than exploding in an uncontrolled manner. Where the octane number is raised by blending in ethanol, energy content per volume is reduced.

    It is possible for a fuel to have a Research Octane Number (RON) greater than 100, because iso-octane is not the most knock-resistant substance available. Racing fuels, avgas, liquefied petroleum gas (LPG), and alcohol fuels such as methanol may have octane ratings of 110 or significantly higher. Typical "octane booster" gasoline additives include MTBE, ETBE, isooctane and toluene. Lead in the form of tetra-ethyl lead was once a common additive, but since the 1970s, its use in most of the industrialised world has been restricted, and its use is currently limited mostly to aviation gasoline.
     
  3. Richard Martin

    Richard Martin LawnSite Fanatic
    Posts: 14,700

    Just buy a name brand (Shell, BP, Texaco, Exxon, etc.) 89 octane fuel for your equipment and you'll be fine. The name brands have the same additives regardless of octane rating. The non name brand fuels often lack the additives of the good gases.
     
  4. bc3xx0

    bc3xx0 LawnSite Senior Member
    Posts: 305


    So walmart gas isn't any good????

    Come on man...... Most gas comes from the same tanks, the only difference is the color of the pump.
     
  5. Richard Martin

    Richard Martin LawnSite Fanatic
    Posts: 14,700

    I wouldn't use it, no. Most of the gas doesn't come from the same tanks. I have been to a tank farm before. The operators are very specific to make sure the right brand of gas makes it to the right gas station.

    I've been here at Lawnsite for 11 years. In all of those years the only fuel complaints I have heard have come from people that don't bother to name the type of fuel they use. You never hear someone complain that they have had a problem with name brand gas. It's only the gas that comes from Billy Bob's, Walmart, 7-11 or the like that seems to cause problems. No name gas lacks the cleaners, stabilizers and other important aspects of fuel like octane consistancy.

    The amazing part is that name brand fuel is the same price as no name fuel. Why would you buy fuel of questionable quality when you could buy good gas for the same price?
     
  6. KINGMADE

    KINGMADE LawnSite Member
    Posts: 237

    I love how people think they get higher gas mileage using the higher octane which is very far from the truth.
     
  7. bc3xx0

    bc3xx0 LawnSite Senior Member
    Posts: 305


    Well then, obviously you are an expert!!!

    I always thought they had regulations on minimums for enviromental reasons that made the gasoline virtually the same, but since you took a field trip to a tank farm, you should know!!!
     
  8. Richard Martin

    Richard Martin LawnSite Fanatic
    Posts: 14,700

    Nope. Not an expert but I do read a whole lot. I also have a great ability to comprehend what I read and am able to figure out a whole lot on my own. Your statement "I always thought they had regulations on minimums for enviromental reasons that made the gasoline virtually the same" for example. Did you even read what you wrote? Do you understand what that means?

    Yes, there are minimum standards for fuels. And if every company only met the minimum standard then all fuels would be the same. But that's where the difference comes in. Your better name branded fuels go beyond the minimums. What I wrote above "cleaners, stabilizers and other important aspects of fuel like octane consistancy" are what make the big difference in fuels. Don't look for a whole lot of that in no name gas.
     
  9. bc3xx0

    bc3xx0 LawnSite Senior Member
    Posts: 305

    Don't look for a whole lot of that in name brand either!! I mean, I haven't took a field trip to the tank farm, but don't believe the hype!! Some times the added detergents aren't designed for carburated lawnmower engines anyways!!


    You don't happen to live on the border of regular and reformulated region do you?!!
     
  10. topsites

    topsites LawnSite Fanatic
    Posts: 21,654

    There is always a reason for cheap.
     

Share This Page