I only use 93 octane fuel in my 2.4 (of course I've had it tuned for a minimum of 93 octane for higher performance).

On a stock engine 91 octane is fine. If you use 87 octane the computer will retard your spark when it senses knock (it's called kr or knock retard) so your engine won't be damaged by the knock.
Yes you can run 87 octane, but your Hp will be down to the 163-165 range not the 171hp your car is rated at.

Read your owner's manual. On page 5-5 it says to 2.4 and 2.0 owners: "...use premium unleaded gasoline with a posted octane rating of 91 or higher. You may also use regular unleaded gasoline rated at 87 octane or higher, but your vehicle's acceleration may be slightly reduced, and you may notice a slightly audible knocking noise, commonly referred to as spark knock"

I don't want decreased acceleration, do you? If you wanted to use 87 octane you should have bought a 2.2, for which 87 is recommended.

I only use mobil 1 (switched to it at 1,000 miles) and change it when the DIC is at 20%.

 

Everything you said is right.. IFF you get KR with 89 or 87. Another thing worth adding is that you will get worse gas milage, because you do not get as much power, meaning to remain at cruiing speed, it will take a little more fuel, although this is REALLY amplified by FI.

But how do you KNOW you get KR with 89, just curious? How do you scan for it?

My lsj didn't even get all that much KR with 89 when I was stock. Now I am tuned for no less than 94, but then again I am running a lot of timing and boost. I log KR with HPT for hour+ strgith runs in all possible conditions and scenraios.

 

I have to disagree. I have used 93 octane every fill up except for one. The one time I used 87 my car ran like ****. In my experience, the car runs better on 93 octane.

 

Oh yeah, Mobil 1 every time.

 

Gasoline emission standards are higher in Canada,it is common knowledge here, as is the quality of gas,maybe it goes hand in hand with being a country that does not import oil. so should I use 91 or 94, 94 is usually .4cents more a litre

 

You answered your own question. The only way to know for sure is to data log.

I tend to trust Chevy engineers when they make a specific octane recommendation for the cars they design and build. I just assumed that they spent thousands of hours data logging kr under all conditions. Of course they must error on the conservative side. After all, they're buying the warranty problems.

For an specific car operated under ideal condttions, you may get by with 89 octane - if you take the time and spend the money to buy HP Tuners and log kr. An enthusiast like yourself might very well do this (out of a desire to understand what's happening inside your engine - not in an effort to try and save a few pennies on a gallon of gas), but the average owner has no idea what we're even talking about. Their best bet is just to go by what it says in the owners manual.

 

the best results are at 91 octane if ur at 10.4:1 compression ratio the 10:1 are best suited for 89 but u might as well treat it like a 11:1 since the extra .4 thats why reccomended 91

 

Static compression is an important factor in determining what type of gas to use, but ultimately, dynamic compression is the deciding factor. Dynamic compression is influenced by ignition and valve timing, static compression, and air density(boost pressure and air temperature). Also involved to a lesser extent are a/f ratio (and fuel atomization method ie. carb, tb injection or direct port injection) and any detonation suppressors/ enhancers like water/meth or nitrous injection Combustion chamber shape, head temp and spark plug heat range/projection also influences knock/detonation.

Suffice to say that the interaction of all these factors it very complex. Kr needs to be measured to determine octane requirements. Formulas will only get you in the right range.

 

Yeah, when I first got the car, the dealer just used 87. It ran like a turd. That was when the 2.4's just came out, so maybe they didn't know that a higher gas was strongly suggested? But I don't mind spending the extra few bucks. The car runs amazing on 93. But I think that i'm just gonna go synthetic when I change the oil. I'm getting the oil fill cap from the s/c too so it says Mobil-1 on the top so whoever gets the car after me remembers. lol.

 

i've thought about that too... just for un-needed bling in the engine area. if i can find a part number, i'll order it.

 

About time some one with some smarts posts a good reply. I run 91-94.

 

synthetic is just plain better than conventional oil. It's basically just chemically enhanced oil to be better for your engine. i put synthetic in all of my family's cars.

 

I run Mobil 1.

And I have put nothing but 89 octane in since day 1, I get anywhere from 25.5 to 26.1 mpg.

 

Use exactly what they recomend you use. Nothing higher nothing lower. Going lower can be unsafe and cause knocking, but what many people don't know is running too high of an octane can cause you to LOSE power and run less smooth. My car for example is tuned for 87 from the factory. I use 89 at a maximum just because it is a higher quality fuel. Using say 93 in my car would just make the fuel burn less evenly and over time if i only used 93 and the fuel burned unevenly i could get carbon deposits, which is not necessarily insanely bad, but it isnt good. If your car is tuned for 89...you arent going to gain any power by going to 93 because your engine does not recognize that it is running a higher octane gas and does not change timing and all to take advantage of the higher octane. You will make the same power using higher octane gas, if you don't lose any.

 

i use the 89 octane on my 2.4 since the lower octane makes the car run like ****. I don't use 93 only because for some reason around here they made the prices 2.50....267...and 3.24 HOLY ****. lol I do notice a HUGE gain fromt he higher octane, and if gas EVER GOES DOWN or I make more money i'd like to run 93 or 4 all the time.

 

Even at 3.25 a gallon, my Coby was sippin' 93.

 

Same here. Mine was still sippin' 94 since all I buy is Sunoco gas.

 

sunoco is not top tier.... oh noez

 

what do you think is then????

 

www.toptiergas.com

I honestly use shell, but its near me so why not. if its a quality brand, it shouldn't matter much. but reviews of this toptiergas thing do seem promising...

fyi... gm uses chevron fuel in detroit.

 

Your exactly right. I log in a LOT of different conditions just to see how the car will react. And I know how conservitiave GM can be, I work for them

 

I'm not saying that BP is the best, but it was the first premium gas (93) that I've ever used. I always fill at the same station if I'm around home. If I'm out, I do my best to find another BP. If not, I'll get a few gallons at another real gas station (Sunoco, Exxon) until I can find a BP. lol. That way if I ever have a problem, i'll know it was their gas. I'm just weird like that. lol. Actually, atmy BP, I even always use the same pump.

 

No BP or Amocco? I always thought BP was rated highly.

 

I only use BP because they do not import Middle Eastern oil. No Blood for Oil!!!

I was a soldier, and am friends with many who now serve, so I'm sensitive to these things.

 

I will only buy top tier gas. And on top of that I am tuned for 94. Therefore I only get Sunoco 94 octane. All sunocos in MI and OH have it.

hmm.. thier not on that site you listed, but I know they are toptier (as per a GM news bullitin I get at work) and it says so on a lot of thier pumps