Long post, I'm sorry, but I came across this site today and figure you all will know better than anyone else. I'm quite in need of help

My apologies if this question has been answered elsewhere, I haven't found it yet, and i'm becoming very frustrated.

I just bought a used 2006 2.4L SS ***non-supercharged***. It had 29,900 miles on it, and I bought it from a large dealership. It the first car I have ever bought (always used a parent's car).

Anyways, my brother bought a 2005 SS/SC brand new, and it requires 91 octane I believe. When I was in the process of getting my 2006, I asked them if it requires higher octane gas than 87. I was told that it did not, which made me happy because I obviously don't want to pay more at the pump.

Problem is, the car didn't have it's manual (I didn't even check, cause I assumed it would be there of course), and I can't find a consensus anywhere online. Does it REQUIRE 91, or is 91 just recommended? From what I've seen, most car's manuals "recommend" higher octane fuel.

I drive quite conservatively in day to day travel, but on my first half tank, I only got 120 Miles. Which is ~20 MPG, and 50% of that was hiway driving. Shouldnt it be much higher? They gave it to me with a full tank of 87 octane.

Lastly, Whenever I shut the engine off, there is a loud ticking noise every 1-2 seconds coming from under the car.

So, the dealership is ordering me a manual but I wont have it for 2 weeks, and need to fill up tomorrow. I don't know what to do.

-Does the car NEED 91? 89? or 87?
-Could the poor milage be due to low octane fuel?
-Is the ticking noise normal or a sigh on a problem.

I'm so terrified I just spent a ton of money on a car that has something wrong.

Thanks to anyone who reads this post and a special thanks to anyone who can help with answers. Looking forward to replies...

Confused, frustrated and in need of help,
~Rome

 

let me be the first to say welcome and 91 is only "recomened" but i say you should because it gets better gas milage and more power really in the end it would be cheaper to put 91 in and we only have a 10 gallon tank its not gonna make much of a diff. anyway and the ticking is the exhaust just cooling off its nothing to be worried about to me personally it sounds cool cause it sounds like you just got done driving fast lol but its nothin to worry about they all do it

o and for more info on the 91 there's a thread about it RIGHT HERE \/
https://www.cobaltss.net/forums/2-4l-le5-performance-tech-46/91-octane-benefits-113373/<<<<<<<

 

Welcome dude.
The exhaust is just cooling off. Mine did that till I got the GMPP catback.
I am not sure you can judge your gas mileage on just half of a gas tank. Gauges really dont measure up that way. I always pick a point on my gauge, fill it, and then drive it till it returns to where I filled it. Anymore I just reset my mileage counter in my dash computer. I run 91-93 octane but I dont remember being told I had to.

 

to get the most out of the car do 91. if its more for daily driving and such go 89. 87 you will have a tendancy to get a little bit of knock in your motor. just my experience.

 

Thanks all for the replies. Good to know the ticking isn't a problem. Thanks for that.

Yes, outtamymind, all my driving at the moment is just daily driving. Maybe I'll go 89 then? Also, outside of what i've read today, I don't really know what "knock" is.

Budz1065, thats a good idea. Fill the tank, mark the gallons, reset the meter, drive to where it was and refill. That sounds like a very sure way to check mileage, thanks.

Also, Is it ok to mix octane's? The car says it's got half a tank in it right now, half a tank of 87. Should I run it empty before trying 89 or 91? Is there anything special to do before changing fuel octane?

 

yea dude run 91 octane or higher bro...ss models need 91 and uo

 

You can mix octanes with no problem at all. If you still have a half tank of fuel, obviously the 91 and 87 will mix and be kind of in between......but it's not a big deal at all.

 

if you really want to read the manual for your car go to http://www.mygmlink.com and set it up for your car... you can find a copy of it on there that you can download

 

i have a 2.4 and used 87 for awhile then moved up to 91 and you can tell the difference in power and i also get better gas millage, but you will be fine with 87 but i figure for the little extra 91 is worth it!

 

the manuals recommends 91, i say go with what it recommends, my gas mileage improved a good bit after i went to 91 octane. If i do all highway i can get 600km out of a tank. With half an half i get about 450-500km

With our tanks being so small, it really doesn cost much more to fill with 91 octane. Couple bucks

 

yea, for the extra $2.60 (~13 gallon tank, 20 cent difference in price)...... the benefits exceed that cup of coffee worth of money....... a tid bit peppier, better gas mileage and the car doesn't get pissed at you

 

Run 89 and you should be fine. I have ran and tested pretty extensively between 89, 91, 92, 93 and there is zero difference in performance or knock. The only mileage differences come from whether it is an ethanol blend or not and at 10% the difference is small (1mpg approx).

I wouldn't run 87 as you are in knock territory and would probably have reduced power.

Premium is a waste of $$ imho.

For reference I get 25-26mpg on all in town driving tanks and 32-33mpg on highway tanks with 89 octane 10% ethanol.

PS
Your poor mileage is most likely due to how you are driving the car. After a little while once you get used to the car you will get better mileage ;-P I had the same problem when I first got my car. You will experience the same "problem" with each performance mod you do.

 

if youre running 89 you might as well run 91..get a credit card that gives % back on gas and you're fine. I get 3 to 5% back on all gas I buy with my AAA credit card.

Since you just bought it, have you checked all the normal maintenance under the hood? Just make sure the dealer did it even if they said they did.

And yeah the loud ticks you hear after turning off the car is just the exhaust cooling off, it is normal. The metal is cooling and shrinking.

I get about 23mpg in my ss/sc but it is probably my driving style.

 

SWmaster, I have been driving like a granny since i got the car trying to see how good the MPG can be. That's why i'm so confused and frustrated with my low MPG.

25 city and 32 highway is what i was hoping for, like your car gets. I guess we'll see. The "Fuel Range" gauge... is that how far you should be able to drive on the gas you have left in your tank? And if it is, how accurate is it usually?

anothersss, I'll look into a card like that, I also have AAA, thanks.

 

I get around 35-36 mpg on the highway with mine......so a stock 2.4 should be able to get around that too. I would expect better than 32 highway mpg.

 

nice car. i bought my 2.4 new from the dealer and they filled it with regular. i had a little knock with it at first, so i immediately switched to premium on the next tank. didnt really notice any power gain or loss, just no more knock. around 15 thousand miles later I switched to regular because of the gas prices. i was afraid of knock, but it didnt come back. Didnt find any gain or loss in power or mpg.

Humidity and air temperature affects my engine the most here....

ohhh p.s. my mpg in the summer is 30 and winter is 27. driving 70-30 highway-city.

 

I always ran 93 in mine.

Mine was tuned though, even before that though...seriously it is like 3 or 4 bucks we are talking about here...and if you are that scrapped for cash, sell the car...

 

welcome to the club dude! ive had my 2.4 for 22 or so months now and not once have i put any less than 93 grade in my car. the manual requires 89? i believe but i treat my car like a baby, its really a matter of opinion, obiviously the higher grade you purchase is cleaner for your car...it really boils down to how willing you are to baby it.

 

Actually premium is not cleaner in any way. Just higher octane which has nothing to do with how "clean" the fuel is.

I run 89 since it is cheaper than any other fuel type in my area and still has zero knock problems. 89 is about 10c cheaper than 87 and about 30c cheaper than any or the "premium" blends. Noting wrong with premium but you aren't doing anything better for your car running that over 89. The only difference in mileage you might get between 89 and some of the premium blends is if you run one that doesn't have ethanol. In that case you would get better mileage.

Have you checked/replaced the air filter?

Oh and the other people in the thread are right about the ticking. The stock exhaust makes that sound. When I changed to my magnaflow system that sound went away.

 

I am in disbelief of what people are saying for their mileage in a 2.4L SS. I did a 15 or so kilometer (9 miles and a bit for my American brethren) and I got 6.3L/100KM which is equivalent to 45mpg. Now I realize this wasn't very far, but still I was surprised as hell to pull that number. I was going exactly 100KM/H (62.5mph) with the cruise set on it. There was some up and down sections, so it wasn't even close to perfectly flat. I was to go on a longer trip to see what it can actually do.

Also, referring to the part up top that is bold, perhaps there is no difference between the refining quality of the gas, but I know up here in Canada if you fill up with premium fuel at Petro Canada, you get some **** called Tactrol in the fuel which is a detergent for your fuel system and I would assume that this will help prevent deposits and other things within your engine. Maybe I am wrong.

 

I Just drove a 350 mile round trip this weekend, 175 miles each way, 90% highway. I have 2 gallons left in my tank. That's a little under 32 MPG over the 11 gallons. Much less than I was hoping for, but better than sticker I guess. The DIC says I got 37.4 MPG though, don't know whats up with that.

Grats on your MPG, sounds like you hit the cobalt MPG jackpot!

 

6.3L/100km might be 45 canadian mpg, but not in US mpg........it would be more around the 38 mph mark. That's why you probably think everyone else is so low.

 

True true...imperial versus metric gallon. 3.78 versus 4.54 liters. When you do with math 45 metric mpg is equivalent to 37.5 imperial mpg.

Still, I am not complaining.

 

Ah, I see what you mean. Around here there aren't any common things for whether a particular grade has or doesn't have an added detergent. Some chains have something and many others don't. The only one I can think of is chevron with "techron". They all name it something different and none of the stations I have seen clearly mark whether there is an added detergent.

Can anyone else name major chains that have cool additives?

 

Doesn't Shell have "V Power", or something like that?