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I've always subscribed to the idea that premium gas doesn't give you any real benefit over regular, unless the vehicle is designed to require it (which the Acadia is not). One exception may be that some premiums may have a better detergent package and may be worth using on occasion. (According to Shell's website, their premium "V-Power" contains 5 times the required detergent concentration, vs. "over 2 times" for the regular and mid grade.) Also, the premium gas has a lower energy content per gallon and should give slightly lower MPG as well, so I can't really think of any reason to use it on a regular basis.

I did an 800 mile trip Thursday and Friday. I took more or less the same route both directions under similar weather conditions. It was mostly interstate type roads, with about 70-75 mph average cruising speeds with a few slow downs for small towns and traffic lights (and the Border Patrol checkpoint). Before I left, I filled up with Shell Premium V-Power. I filled up on arrival and put in 19.01 gallons for 390.1 miles. (20.5 mpg with Premium) I filled up with Valero regular gas ($2.45/gallon in Brownsville, TX!) and drove home. When I filled it up again, I put in 18.44 gallons for 385.2 miles. (20.9 mpg with Regular)

Assuming some minor errors in the way the various pumps shut off and differences in the actual trip, AC load, etc., this pretty much confirms the theory that Premium doesn't really do anything for you, except cost more under normal driving conditions. There may be some benefits when trailering or under heavily loaded conditions but I'm sticking with regular gas for normal driving.
 

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My mechanic used to tell me to put premium once in a while to "clean out the injectors".

Actually, now that I think of it, doesn't premium gas burn slower? Which means that there might be incomplete combustion, which would then tend to dirty up the injectors? So premium probably has more detergents because it doesn't burn as clean!

I guess premium might be useful if you're taking a road trip in the rockies: less tendency for knocking while going up those hills. Apart from that, I wouldn't bother in the Acadia.
 

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I just read an article on regular vs premium in vehicles that don't require premium. The article stated that unless the vehicle was designed to use premium or you are having problems with detonation, there is no advantage to using the higher grade. In fact the article went on to say you could experience slightly less performance, possibly a little harder starting, and even a rougher idle. According to the author this is due to the slower burn rate of hightest vs regular.
 

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big bear craig said:
I just read an article on regular vs premium in vehicles that don't require premium. The article stated that unless the vehicle was designed to use premium or you are having problems with detonation, there is no advantage to using the higher grade. In fact the article went on to say you could experience slightly less performance, possibly a little harder starting, and even a rougher idle. According to the author this is due to the slower burn rate of hightest vs regular.
All quite true but the Acadia manual does say that the use of mid grade fuel when loaded and towing will deliver better performance. What this tells me is that the ignition is tuned right at the edge for regular gas which is no surprise considering the compression ratio of this engine. When it crosses that edge, as it will under towing or just hard accelleration in heated conditions, the knock sensor will hear the onset of detonation (which will never be heard by ear) and dial back the timing and performance a bit. When and how often this occurs is of course the real question. Certainly for normal running down the freeway there will be no issue, but for me, I don't mind putting the mid grade in for loaded trips or some of this 110 degree summer heat we often get. I'm not bashful in stepping on the gas and I don't want to wonder if I'm giving up a bit of the already marginal perfomance when I put my foot in it on a hot day. I use both regular and mid, depending on season and my expected driving, which is really what the manufacturer recommends to begin with.
 

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I read the manual when we received the car, and have been using the mid gas. Haven't tried Premium, then again we haven't towed anything yet.
 

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I would agree with you 100%. If my vehicle was pullling a trailer or other unusual conditions such as really hot weather, or the car loaded down, I would use a higher octane. If the computer detects detonation it will retard the ignition to supress the knock which in turn would reduce the engine power. Under normal conditions 87 octane should work ok.
 
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