Chrysler 300C & SRT8 Forums banner
1 - 20 of 31 Posts

·
Registered
Joined
·
643 Posts
Discussion Starter · #1 ·
If the manufacture of your car says to use 87 octane, is there any positive or negative effect if you use 89,91, or 93 octane?
Of course many people say use premium (93) for more power and for teh engine to run cleaner and blah, blah, blah

Others say use whats recommended, anything higher prolongs detonation of the fuel during combustion

What do you think

Discuss....
 

·
Premium Member
Joined
·
2,861 Posts
Higher octane should not hurt . It may on some vehicles be a waste as they are not tuned or set-up for aggressive timing. THe higher octane is more anti-knock so timing can be advanced yeilding better performance. That's my take
 

·
Premium Member
Joined
·
4,252 Posts
Typically premium fuel is HARDER to ignite, thus retarding pre-ignition. This is only beneficial when compression is high and timing is advanced.

Otherwise it's a terrible waste of money.

Now in my area there is sometimes less Ethanol in the high test fuel which can make you get a bit better mileage.

FWIW we could barely tell when my wife accidentally filled the SRT8 with regular!
 

·
Registered
Joined
·
17 Posts
Typically premium fuel is HARDER to ignite, thus retarding pre-ignition. This is only beneficial when compression is high and timing is advanced.

Otherwise it's a terrible waste of money.
X2. My car (lowly 2.7L) specifies 87 octane and feels less reponsive with higher octane fuel.
 

·
Registered
Joined
·
4 Posts
this was exactly what was going through my mind all day yesterday and today.. as i just picked my self a 300C yesterday and wasnt sure which octane to pump.. so which one would you guys recommend??
 

·
Premium Member
Joined
·
2,861 Posts
If you bought the C-Chrysler recommends 89
 

·
Registered
Joined
·
42 Posts
I drive a C so i'll start using that one then. but what if you get a predator, does it make a big enough difference then, if you dont have any other mods? I'll be getting one in the next few weeks, that's why im curious.
 

·
Registered
Joined
·
643 Posts
Discussion Starter · #9 ·
Also
WOuld it hurt any if you switch between 87 & 89 octane?
 

·
Registered
Joined
·
562 Posts
Also
WOuld it hurt any if you switch between 87 & 89 octane?
87 nor 89 octane will work just fine i have tried both in my C. i cant tell any difference in performance so i use 87 with no problems and IMO its a wast of money to put in a higher octane except if you are running a tuner.
 

·
Registered
Joined
·
643 Posts
Discussion Starter · #11 ·
87 nor 89 octane will work just fine i have tried both in my C. i cant tell any difference in performance so i use 87 with no problems and IMO its a wast of money to put in a higher octane except if you are running a tuner.
That's what I was thinking.
But if the manufacture recommends 89, I would assume it's for a reason.
Sometimes I use 87 and I have not noticed a difference either
I just want to make sure I'm not screwing something up
 

·
Registered
Joined
·
5 Posts
I have a 06 C AWD: can’t seem to notice a performance difference between 87,89 and 91 but the higher octane fuel does seem to yield better gas economy
 

·
Registered
Joined
·
17 Posts
Maybe related... my GF's '92 Nissan 300ZX owner's manual recommends 96 octane (remember that?). It says if you don't run 96 you should keep rpms moderate.
 

·
Registered
Joined
·
2 Posts
I've been driving a 300c since Reagan died in May of 2004. I've used 87 octane because I hadn't read my manual. I haven't any problems except the problem with the car shutting down after a fill up. After reading other posts I won't completely fill the tank. Like I said I've had this car since May of 2004 and I still enjoy long drives with it. This is a fine auto.
 

·
Registered
Joined
·
98 Posts
Just to be clear the manual at best "recommends" using 89 octane. It clearly implies that 87 octane is acceptable and considering the rather substantial cost difference I use the 87 and have over 250,000 trouble free kilometres on my C. Trouble free, that is, except for the infamous front end suspension issues these cars are prone to, ugh!
 

·
Premium Member
Joined
·
656 Posts
Just to be clear the manual at best "recommends" using 89 octane. It clearly implies that 87 octane is acceptable and considering the rather substantial cost difference I use the 87 and have over 250,000 trouble free kilometres on my C. Trouble free, that is, except for the infamous front end suspension issues these cars are prone to, ugh!
Is that more reliable than a vague statement of fact? :)

You approach a convenience store. An assailant is holding a gun to the cashier's head. You say "I recommend that you not shoot that woman." The assailant puts the gun away and pulls out a knife, then stabs the cashier to death. You subdue the assailant until the police arrive. The first words out of the assailants mouth is "Honest officer that man clearly implied that I stab her!"

The full consequences of you inferring more than you should from the manual's recommendation on octane has probably been prevented by your PCM's ability to compensate by pulling timing and adding fuel when the need arose. My recommendation for you is not to run WOT at peak torque on a hot summers day if you continue to interpret the manual the way that you have.

*I have not read the manual. I base my discussion only on what you have implied. :)
 

·
Registered
Joined
·
643 Posts
Discussion Starter · #17 · (Edited)
I took this directly from my manual
Now No one has to go by assumptions or by the implications of others


From what it states, 87 is acceptable, but for best performance use 89


 

Attachments

·
Registered
Joined
·
644 Posts
our fuel here is 95 an 98 (Norway), I have even used 100% on my Harley in Holland
 

·
Premium Member
Joined
·
656 Posts
I took this directly from my manual
Now No one has to go by assumptions or by the implications of others


From what it states, 87 is acceptable, but for best performance use 89
Now you've gone and ruined all my fun...of which I had clearly implied I was having. :)

There are a lot of variables that the manual cannot predict including altitude, humidity, ambient temperature, engine temperature, all of which can significantly encourage detonation. I would caution anyone from blindly following any octane recommendation without regard of their current situation. Someone in Houston during August with the oil temp in the mid 200s might well observe the higher end of the recommended octane. In most cases the practical consequence of using a step lower octane gas is that your LT knock retard will rob you of significant power but in extreme cases it could be much worse...
 
1 - 20 of 31 Posts
Top