So my cars running fine every things good. I have a little less than half tank. I decide to go fill up at shell instead of sunoco cause I read that sunoco actually isn't a top tier gas. So I put 7 gallons exact of shell 93. Whatever was left in the tank was sunoco 91. I didn't think mixing the 2 especially with not much 91 left would hurt anything. I was wrong. Last night my CEL comes on. I'm like WTF? Go to auto zone today and they said 420. First of all that doesn't make any sense. If I would of gotten that code it would of been over a month ago when I put my ZZP downpipe on. So something else has to be wrong. I jack the car and start it. I get under and feel for leaks and visually look as well. I don't see or feel anything. Then I hear something. I hear what I think maybe is a leak from the flex pipe but I don't feel anything. I turn the car off it goes away. Then I turn the car on and listen some more. I think it's knocking! It sounds like little pebbles hitting metal. WTF!!!!!!!! Is this from mixing gases???? Think that maybe gave me my CEL? There's no way a month old cat can be bad. Especially when I really don't beat on it much. I have 15k miles. Maybe I should run seafoam thru in case its carbon build up? I do mostly city driving.

 

why are you using 93 octane? if anything its hurting you if your not tuned for it. maybe your car is running rich and it plugged up your cat

 

i may be wrong, but i thought the owners manual called for 93 octane.

 

not hurting anything. It wouldn't run rich either

he has a 2.4 n/a


It would be odd to say that your gas is the problem, hook it up to a scanner and check kr?

 

i realized that right after i posted. guess i should pay more attention before i post next time.

 

i dont have a scanner only autozone does they said 2 420 codes unless my car is high idk... and i went to 93 cause shell doesn't have 91 and is supposedly a better gas

 

hes a 2.4 not a 2.0. it could possibly not be burning all the fuel

 

ehh. don't feel bad, I'm not one of those **** that screams "oohhh, you should of paid more attention to the OP" or "use the search button!".. I hate homo's who do that ****.

 

the pops the exhaust makes when shifting does seem to be louder...

 

You don't have to have a tune to run 93...

 

the 2.4s can only run 93 i put 87 when i got my car and a check light come on , i toke it to the dealer and they told me what gas did i put i told them 87 and they told me i can only put 93 .

 

wow.

 

Dealer is a retard then. An 2.4 can take 91,87,89.. Not only 93 lol.

 

troof.

 

i have the owner manual in my face,so this what it say.if your vehicle has a 2.4l L4 engine or 2.0l supercharged engine,use premium unleaded gasoline with a posted octane rating of 91 orhigher.you may also use regular unleaded gasoline ratedat 87octane or higher,but your vehicle's acceleration may be slightly reduced,and you may notice a slight audible knocking noise,commonly refrerred to as spark knock. i hope that helps.

 

If your hearing "pebbles or noise" in your downpipe, likely your cat is coming apart internally, it's no fault of your own AND guess what if your under I believe 80K miles it's covered under your EMISSIONS warranty and that is federally mandated and has it's own little column under warranty coverage in the back of the manual, so take it in to a reputable dealer and they will observe your cat efficiency and likely replace it free.

 

thats true but i wouldn't run 87 its got high compression it's gonna knock all over the place but why the hell am i knocking on 93?

dealers not gonna replace zzp downpipe lulz my dp is only a month old and i bought it brand new from zzp

 

maybe it was bad gas. try draining it and gets some new stuff. mixing them shouldnt have been a problem and increasing octane shouldnt be causing knock.

 

i can't afford to do that... lol

 

ok my friend came by whose a tech at chevy. he said its deff knocking but its really not that bad its not on rhythm so its not valve knock. he said it could just be bad gas but idk i hope so. maybe i should try seafoam maybe theres carbon build up. cause if its not valve knock then it's gotta be detonation/pre-ignition. and I know that can occur with carbon build up

 

I think the owners manual calls for 91,
Also from the way i understand octane, if you mix two, you'll just get the average of the two you mixed. ie: 93 and 91 should give you 92. (Assumeing you mixed EQUAL quantites)

But ya, could be the CAT. From what ive heard on here, these cars do have issues of eating cats for lunch. And I dont mean Felines either....
.
GM put out an warranty extension on the Cat because of it. I baught my car with 35000 miles on it, and in the history it had already had its cat replaced.

 

not stock cat

 

93 octane doesnt hurt your car. if anything its better for it because it aids in efficiency and....from my experience....helps the motor last longer. i've been running it in my car since i bought it and i've had no problems at all.

 

sooo should i stick with it or go back to 91

 

I think some of you aren't seeing what's really happening here.

The P0420 code is for cat inefficiency. The rattling noise he speaks of is the first thing one notices when the stock cat is going bad. The down side of that is that it's already very restrictive, and has a tendency to then over flex the flex pipe as the cat goes back.

So really you probably have a combo of bad flex and/or cat. the extra downside of this is that if you go aftermarket, you'll get the same code as the aftermarket cat will be too high of efficiency and the dummy sensor will throw the inefficiency p0420 code again. to fix this once side effect once you go aftermarket, you'll want your tuner to delete the p0420 code all together.

This seem to be making sense to you?