I read this just now on another forum and stole it. It is by a former petroleum something or another, don't know what he did. But this is interesting. It may slightly apply to saws, but it is really general info, and I'll follow with another of his posts in just a second....
"Yes I retired from BP, moved on to do other things (like get back to flying!).
As far as gasoline products today, there is nothing as differentiated as the old Amoco premium was. (actually if you live in Germany, BP's premium diesel there, sold as Aral, is a highly differentiated fuel, but I digress). Everyone is using essentially the same refinery blendstocks, so the difference is only in the additive packages and the octane. These days, modern engines almost all have knock sensors (certainly the higher performance ones) and so if you buy lower octane, you just get lower performance, not detonation/knock. Typically, for a well tuned engine the enhanced performance (due to spark advance by the ECM) will give enough better performance, showing up in mpg, to just about offset the cost difference for premium vs regular gas (ie performance for free). It is not easy to tell this by checking your own result, but is easily measured across a fleet of 100 cars doing thousands of miles (as we used to do).
In terms of additives, they are all made by a few companies, like BASF or Afton, bought by the marketers, and blended in at the terminal where the trucks fill up. In some cases the additives are made to proprietary specifications for a given marketer. Thus BP, Shell, Chevron, and XOM all will have somewhat different additive packages in their fuels (or at least in their premium fuels). The additives help keep deposits from forming and in some cases help to remove existing ones, keep thing generally clean, etc. They don't really have any direct effect on combustion (unlike TEL, which does).
FWIW, I normally buy BP or Shell premium in the midwest, or XOM is OK, and nothing else unless stuck. Never paid much attention to Sunoco, their market share was too small to matter, but they did typically sell premium (if you put their blend pump to the highest setting) that was one octane number higher. However, a lot of engines actually won't advance the spark enough for that difference to matter. I drive an M5 that has been Dinan-modified, so the chip will take advantage of all the octane available."
Ok, here's his answer to another poster's question [on that forum] as to why autogas goes bad faster than avgas:
"It's all about the molecules in the refinery streams that are blended into the gas. For auto gas, there are a lot of "cracked" streams that are more reactive and thus more likely to form gums, deposits, etc. Avgas is made to be stored for long periods and so these streams are not used.
If you want to store auto gas for more than a month, you should add one of the stabilizing additives available at the parts store etc, (Stabil is one brand). It will make a big difference."
This isn't anything real new for this saw forum, many have said these very things. I just thought it was interesting to read it coming from a pet. professional....
"Yes I retired from BP, moved on to do other things (like get back to flying!).
As far as gasoline products today, there is nothing as differentiated as the old Amoco premium was. (actually if you live in Germany, BP's premium diesel there, sold as Aral, is a highly differentiated fuel, but I digress). Everyone is using essentially the same refinery blendstocks, so the difference is only in the additive packages and the octane. These days, modern engines almost all have knock sensors (certainly the higher performance ones) and so if you buy lower octane, you just get lower performance, not detonation/knock. Typically, for a well tuned engine the enhanced performance (due to spark advance by the ECM) will give enough better performance, showing up in mpg, to just about offset the cost difference for premium vs regular gas (ie performance for free). It is not easy to tell this by checking your own result, but is easily measured across a fleet of 100 cars doing thousands of miles (as we used to do).
In terms of additives, they are all made by a few companies, like BASF or Afton, bought by the marketers, and blended in at the terminal where the trucks fill up. In some cases the additives are made to proprietary specifications for a given marketer. Thus BP, Shell, Chevron, and XOM all will have somewhat different additive packages in their fuels (or at least in their premium fuels). The additives help keep deposits from forming and in some cases help to remove existing ones, keep thing generally clean, etc. They don't really have any direct effect on combustion (unlike TEL, which does).
FWIW, I normally buy BP or Shell premium in the midwest, or XOM is OK, and nothing else unless stuck. Never paid much attention to Sunoco, their market share was too small to matter, but they did typically sell premium (if you put their blend pump to the highest setting) that was one octane number higher. However, a lot of engines actually won't advance the spark enough for that difference to matter. I drive an M5 that has been Dinan-modified, so the chip will take advantage of all the octane available."
Ok, here's his answer to another poster's question [on that forum] as to why autogas goes bad faster than avgas:
"It's all about the molecules in the refinery streams that are blended into the gas. For auto gas, there are a lot of "cracked" streams that are more reactive and thus more likely to form gums, deposits, etc. Avgas is made to be stored for long periods and so these streams are not used.
If you want to store auto gas for more than a month, you should add one of the stabilizing additives available at the parts store etc, (Stabil is one brand). It will make a big difference."
This isn't anything real new for this saw forum, many have said these very things. I just thought it was interesting to read it coming from a pet. professional....
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