2010 Chrylser 300 with 3..5L H.O.- Mid Grade or Un

[Topo]

My owners manual states 87 octane, but I can pull up a chrysler 300 pdf(Internet) file owners manual for 2010 model year and it states recommended 89 octane, 87 is Ok. In 2009 versions and lower with the 3.5 Liter H.O. the owners manual states 89 Octane. So did they do something different with engine in 2010? Seems to run smoother and quicker response with mid-grade.

 

[Hokiefyd]

I would use at least midgrade. You'll likely find that your fuel economy is better with midgrade also. Our MDX recommends premium, but says that regular is okay to use. I've run regular in it a few times, but like you experience with your 300, the engine just isn't as smooth or peppy. Our cost/mile with premium is nearly the same as with regular because the economy is better. It's not quite even, but it's close...much closer than the difference in fuel price would lead you to believe.

 

[rshaw125]

I believe the 3.5 has a knock sensor. So running 89 may allow the ECM to advance the timing a little. A few extra horses when you need it. As for mileage the only way to really know is to check it several times. My 2006 Explorer had no apparent mileage improvement from higher octane. So its diet is strictly Costco 87.

 

[beast3300]

If it was me I would use premium but since that wasn't the question asked then my answer would be midgrade.

 

[SrDriver]

I have tried 87, 89, and 91/93 Octane fuels in my wife and my past and present vehicles and can not tell any difference. Mileage is the same.

Did notice that when we lived in Wisconsin that it seemed that with 87 octane that vehicles started better during the long Winter months.

I would go by the owners manual.

 

[rshaw125]

I think that a small minority of vehicles may benefit from higher octane gas. But for the majority it's a complete waste of money.Higher octane just means that it resists detonation more.

 

[RamFan]

My Charger's manual says 89 recommended but 87 is optional. I've only ever used 89.

 

[Topo]

Guys! my question was why does my owner's manual say 87 octane, and other 2010 copies of the owners manual state 89 octane recommended. In addition all Chrysler 300 with the 3.5 liter H.O. prior to 2010 model said use 89 but 87 ok. I also changed to 89 octane as soon as I hit 50,000 miles or around there I heard some spark knocking occuring, it could have been a bad batch of gas or something.

 

[Clevy]

Your engine comes equipped with knock sensors. If you put premium in the tank the engine will advance timing til it senses knock then slightly retard it. It will give you a few extra hp. I know the mustangs have 412 hp running premium but if you run regular the knock sensor will retard timing which ends up giving the motor just over 400 hp. Yours likely has the same type system.