I just posted this over on the octane gas test thread.
http://opeforum.com/threads/octane-gas-test-661.1847/
but I think it's very relevant here.
A gentleman who works at a refinery PM'd me with some interesting info...
The different temps may be due to the differences in blend components when it is "assembled" at the refinery. The high speed blending unit we have at the refinery I work at is very accurate and automated, but the blend components change depending on season and what is in the inventory in the tank farm.
Good test Redbull, thank you.
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I asked some questions and some more response...
In our blending plant they make each octane grade ( Three grades) to the government specifications for Octane, contaminant/water , Vapor pressure, non corrosiveness, etc. So the higher octane fuel typically uses more of the high octane components to make it which are usually more expensive to make. They also add products to prevent corrosion and help lubrication if needed. This is all before it gets loaded into the trucks.
Once it gets to the truck rack and is ready to be loaded onto the truck, the proprietary additive package is metered and mixed into the fuel as it is loaded into the truck tanker. ( Shell additive, Chevron additive, generic additive, etc.) So until it is on the truck, it is a standard blend for this refinery meeting the Government specs. The additive packages really do make a difference on things like engine cleanliness and lubrication. (There is a minimum spec that even the generic gasolines have to meet to be sold on the market : Costco, Fred Meyer, etc, all meet that spec with the generic additive) The generic is not a bad additive, it is just not as good as the top tier additive and is typically metered in at the lowest level to meet Govt regs). I use generic quite often and just throw in some fuel system cleaner once in a while.
So far as the color differences, some additive packages have different dyes or colorants in them to make the fuel distinctive in color. The different refineries all blend a little different depending on how they are set up so far as blend components also.
The test results that surprised me the most was the temperature differences..... so I think it is probably the blend components coming out of the tank farm that are different depending on which refinery makes the fuel. ( The blend may effect the temp being produced by the saw I suppose). Some components are higher octane, or cleaner coming from each different unit in the refinery. Some refineries are short on one product or long on another, so they use as much of the stuff they have lots of, and as little as possible on the stuff they are short on. So in the end, they meet the government specs at each refinery, but the component blend will vary somewhat by facility. Nothing bad or good is trying to be done, it is just how the places work
So, you might find one brand at a station that gets their fuel from a refinery that your saw really likes or just down the road another blend from a different refinery that your saw doesn't like. Then it changes over the seasons because of cold weather (RVP numbers) They put more light stuff in during winter so the engines start easier.
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Redbull says -
So 91 would be less corrosive and have less contaminants than 87 or 89?
So 91 should run cleanest? Vs 87 or 89 (most likely)
So 91 should have a little more lubrication than 87 or 89?
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His response...
The 91 89 and 87 will all be about the same for corrosiveness, they just need to meet a minimum standard so they do not harm a fuel system,
the 91/92 octane that Shell sells has a lot more detergents in it than the 87 and 89 since it is their flagship product, but all will help clean a cars engine inside ( Carbon on injectors and combustion chamber, pistons, etc.)
I am not sure about other brands of gasoline. Some may just be higher octane with the same amount of detergents. Chevron and 76 also have very good additives from what I have heard.
The lubrication standard is also a government minimum type thing, so I think the lubricity would be very close between the different octane grades.
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Redbull says -
here I found something...gotta think about it for a bit... " Buy gasoline during coolest time of day - early morning or late evening is best. During these times gasoline is densest. Keep in mind - gas pumps measure volumes of gasoline, not densities of fuel concentration. You are charged according to "volume of measurement".
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His Response...
Yeah, that makes sense that you would get more gasoline for your buck when it is cold.
I run premium fuel in all my outdoor power equipment..... I think it is well worth the small extra bit of money.
