so ... in theory it would be best to simply buy 89 or 93 octane. Not because it would have anything to do with mileage, but because it is a 'cleaner' fuel no matter how you look at it ... and even though you get no instantaneous benefits from it, you get a long term benefit of knowing you have a cleaner engine.

I personally don't find the 10-20 cent difference matters anymore. It did when I was paying $0.699-/gallon (where the difference of 11 gallons would be an extra 3+ gallons between reg & prem.), but at $2.339+, not only is it less difference than the cost of 1 gallon, but if I don't buy a frappachino/soda/water on that visit and I get the difference back anyway, and it also equals the amount of one of the 'every time you fill up' additives without having to put it in (or walk in and buy it if you use credit/debit card).

I don't know the effects of a higher octane on a lean-burn engine, or the store bought additives (cheap every tank ones or the only use once every 3000 miles ones). I did notice in the manual to use AT LEAST 86 octane or above, but had no limit of how high of an octane you could use. So to me, premium is ok as far as they are concerned, but no reasonable benefits in thier opinion of you using it. Also, isn't the fuel in Japan on ALL levels have a higher octane level than in the USA? I will try to look it up, I don't remember where I read it so I will try to find it.

As far as shady gas stations, it was more of curiosity of whether an independant owner would try to make that extra buck. They control the mixers, so they can adjust if you are getting 89 or somewhere higher or lower than that figure.

With waiting a day to fuel. That would be nice, but we have some that refuel everyday. A lot of high fuel consumption vehicles here (think jacked up trucks with oversized tires, hummers, suvs, dualies, old cars, camaros, etc). Most of the stores are closed at night, but the truckers don't schedule themselves to drop after or at closing or I would do all of my filling in the morning to be safe. So it is kind of a crap shoot and hope you get lucky and see the tanker before you pull in or hope that he was there several hours before.

again, when I was working at the city fleet gas station, If no one would come in during the dump or around an hour afterwards, it seemed to be fine. But, if he dumped the fuel when it was busy, I would end up having to change out most of the pump fuel filters that day. It seems that even though they are on the clock (and stereotyped of being lazy) they hated wasting their time filling up on a slow gas pump (except for maybe a couple who enjoyed the excuse for the break). It would sometimes become rediculous though, slower than a gallon a minute or more. So ... you do have SOME protection from the bad gas, but those filters only stop so much, and I think stop some water too. They look very much like a common oil filter on a normal sized car, the diesel ones are a little bigger and much taller/longer.

Sorry if I am not writing properly, kinda tired but can't sleep

I just want to thank you again GoNavy, I appreciate the facts AND opinions.