Do you use 87 or 89 octane?

[boro]

Just curious. I know this has been hashed over before, but I want to see what everyone uses and if they noticed a difference. My car has been filled with nothing but 87 for the two tanks I've had it (3.6 V6) but I want to put premium in it at the next half tank so that it balances out to midgrade, and see what happens. So what do you use, and did you notice a difference?
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[MalibuKen]

Originally Posted by boro

So what do you use, and did you notice a difference?

I have tried a couple of tankfuls of 89 in my I4 and noticed absolutely NO difference......power or mileage.

[Rodents]

The 3.6 can run on 87 but 89 is recommended. Reason being you're running 10.2:1 compression, a wee bit high for 87 octane fuel. The only difference is the ECM will, in certain circumstances retard ignition timing a bit to reduce pinging. You won't hear the ping, that's picked up by the knock sensor. A big difference, I would say most of the time it's not the end of the world, may be noticeable though. I run premium fuel in mine pretty often. There's a station close to me that takes a nickel a gallon off of premium on Friday. At that point the difference in price is sometimes less than a nickel a gallon between 89 and 93. If I need fuel at another point in the week, I usually just put in 89. I also try to run TopTier fuel when I get close to a station that has it without breaking the bank. Most of the stations that carry TopTier fuel here are about 15 to 20 cents a gallon higher than other stations. A bit more than I feel is justified.

[Cizzle714]

I run a programmer from PCD (Performance Chips Direct) and turn it all the way up. I run 93 in my I4 and there is a slight difference in the performance. Better throttle response and i get between 24-25 mpg with it around town. I can easily do 500 miles on a tank on a road trip and have even gotten 400 driving around town but that's being very nice with the gas peddle.

[DrivenDaily]

I run 89 in my 3.6 V6. When I had my '09 3.6 I tried 87, 89, and 93.

The 87 runs but I can tell the difference between it and 89, and I was able to measure the difference. I don't have the records for my '09 anymore so I can't give you hard numbers.

The 89 is the best cost per mile. Performs better, gets better mileage, feels stronger. Mind you not much, but when it ran on 87 it was obvious when I put 89 back in.

The 93 did not perform better or provide better mileage, so I figure it's just a waste of my money.

I run Top Tier brands almost exclusively.

[boro]

Thanks for the input guys! I'm going to try filling up (from half tank) with premium from Shell tonight and see if it makes a difference.
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[EnvoyBu]

I'm with Driven here. 89 is the best option. 87 runs like crap for me, but 89 makes it oh so much smoother! More power and better mileage as well.

[JimD]

Originally Posted by boro

Thanks for the input guys! I'm going to try filling up (from half tank) with premium from Shell tonight and see if it makes a difference.
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I would be very surprised if you will be able to document any difference in fuel cost per mile based on one or two tanks of different octane fuels.

Performance and "feel" differences are too subjective to measure without before and after drag stip timing slips or dyno numbers.

IF fuel cost per mile is your concern, you will be better served by maintaining a long term spread sheet using your trip odometer mileage and the exact quantity of fuel at each fill-up. Long term = 3,000 to 5,000 miles; longer is better - the differences between filling station auto shut-off mechanisms tend to get smoothed out over time.

And since cost per gallon is a moving target what you REALLY want to measure is the difference in MPG as you experiment with different octane values.

As an arbitrary example of what I look for, IF the price per gallon difference between 87 octane and 89 octane is 5%, I would expect to see a 5% increase in MPG. The key to measuring is long term data collection.

[boro]

Jim, you're completely correct about that if I wanted to track any long-term changes in mileage. Since I'm so new to this car and I'm going to immediately make the switch, I'll probably never know. But we'll see what the mileage looks like from here on out.

So far, it looks like I'm getting 18 pure city (tons of stops, going less than 20 mph it seems) and 24 mixed. Not bad.

One of my other concerns is avoiding potential damage by supplying the engine with the the optimal octane, as well as letting the engine perform to the fullest of it's potential.

Good news is, I found a top-tier gas station (Shell) that costs exactly the same as the cheap stuff I've been using. Never had a problem with the cheap stuff in the past, but I feel like my Bu deserves the best...
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[MrRichRod]

I ran two tanks of 87 in my '12 2.4L and then the boss offered to fill up my tank for some work I did for him. After almost running the tank empty I filled up and ran a tank of 89 and didn't notice too much, if any difference. Tonight I went back to the 87 as the gas prices appear to be creeping back up to the $3.50/gal mark around here.

Perhaps I didn't run enough to allow any change to occur, but then again I'm not racing around town with the pedal floored either. MPG were similar. (1/2 around town, the other half was highway)

We also run 87 in the V6 but that's never been a problem... almost all the miles put on the '09 are from highway commute.