PDA

View Full Version : What is mid-grade unleaded?


east tx skier
04-18-2005, 10:48 AM
Okay, in the octane thread, there were claims that 89 octane (mid-grade) was a combination of 87 octane and 93 (or 91 octane). In other words, your local gas station doesn't have three separate tanks, but rather, will mix the high and the low octane unleaded gasolines when you select mid-grade gas.

Is this true? It just sounds like a mass email I'd get that I'd later read was a hoax. Is this really all mid-grade unleaded is?

BrianM
04-18-2005, 11:03 AM
According to this web site

http://www.energyquest.ca.gov/story/chapter18.html

They say that it is mixed from the two tanks. Don't know if it is true for all gas stations, brands, states, but it looks like it does happen this way at least in some circumstances.
This is very interesting. I had never heard this until the post on this site.

east tx skier
04-18-2005, 11:23 AM
Thanks, Brian. So if that's the case, does that really amount to an octane rating of 89. Perhaps an explanation of what is added to make it burn slower, i.e., higher octane is in order. If, other than that additive, it's just gas, then it'd make sense that mixing the two different octanes would, when mixed, average out an octane rating somewhere in the middle.

/pardon my ignorance on the subject

Ric
04-18-2005, 11:59 AM
Thanks, Brian. So if that's the case, does that really amount to an octane rating of 89. Perhaps an explanation of what is added to make it burn slower, i.e., higher octane is in order. If, other than that additive, it's just gas, then it'd make sense that mixing the two different octanes would, when mixed, average out an octane rating somewhere in the middle.

/pardon my ignorance on the subject
after learning about the mix on this site I asked a friend in the biz and he said his are 3 seperate tanks and are purchased as reg, mid and super but there are some stations that have blenders to do as you described.
He is a privateer, but says many many stores you go to are leased in some way and those guys don't have a whole lot of idea what they have even if you ask them.

djhuff
04-18-2005, 01:22 PM
I came to this conclusion when I was at the station and saw only 2 analog counters on the pump. Went back 3 times and each time I tried a different gas and watched the counters to see which one was moving. When I bought low grade, the counter with the much higher number moved, high grade the other moved, mid grade, they both moved in a ratio of 2 to 1.

LakePirate
04-18-2005, 05:32 PM
According to my old college roomate who works for racetrack (here in the south) they are a discount gas station. All gas starts out the same and is combined with different additives to get to become Cheveron, Texaco or what ever. If memory servers me correctly the 89 octane means that the average octane is 89. He has told me on occasion that he has bought 93 octane and sold it as 89 because it was cheaper to buy wholesale than the 89. So you could get higher octane that what you are paying for.