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The manual states that 89 octane fuel is recommended for the hemi. However, in my area there is only 85, 87, or 91 octane. They relate to unleaded, unleaded plus, and unleaded premium. So what is the choice to make? Slightly higher or slightly lower octane? What has anyone been experiencing?
 

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My manual states 87 octane is acceptable so I would go with that. I have been using 89 octane but decided to try a tank of 87 on the last fill up. I have not noticed any difference in performance but I don't really push the HEMI. I have not checked the fuel economy with the 87 octane to see if there is a noticeable difference as compared to the 89 octane.
 

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I've used only what the manual recommended (89) but if that wasn't available I personally would try the next lower. Or if I have enough gas scoot to another station, joke :) .
 

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The manual states that 89 octane fuel is recommended for the hemi. However, in my area there is only 85, 87, or 91 octane. They relate to unleaded, unleaded plus, and unleaded premium. So what is the choice to make? Slightly higher or slightly lower octane? What has anyone been experiencing?
I am guessing you live in Colorado or another high altitude place. The 87 octane there is equal to our 89 octane. The altitude makes the difference. If it calls for 89 octane, when you hit the lowlands (down out of the clouds :p ), you need the 89 octane then.
Good Luck
 

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Very good question IMO. Don't have that problem here in the lowlands of the Arizona Desert.

If I were you, I would contact Chrysler via email and get an "official" response from them - then save the email, and do whatever it says to do. Here's a link directly to the email form to contact Chrysler: http://www.chrysler.com/wccsapp/uni...orms/us/webform.jsp&promotion=null&category=U

Good luck! Let us know what DC says.
 

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bos447 said:
The manual states that 89 octane fuel is recommended for the hemi. However, in my area there is only 85, 87, or 91 octane. They relate to unleaded, unleaded plus, and unleaded premium. So what is the choice to make? Slightly higher or slightly lower octane? What has anyone been experiencing?
Manual states 89 recommended, 87 acceptable, in earlier posts someone stated 93 could actually damage the engine something to do with MDS. The last thing you want is MDS FUBAR :eek: (FOULED UP BEYOND ALL RECOGNITION). Of the three choices you list, the only reasonable choice is 87.
 

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You have it flipped...

Just one reference ... http://www.type2.com/library/engineg/ping.htm

"Pinging sounds like rocks being thrown around inside your engine. It will never happen at idle, may happen at part throttle, but is most likely to happen at full throttle. It is usually accompanied by a small amount of smoke out of the tailpipe, but don't rely on that.

Pinging is like... taking a cutting torch to your combustion chamber. Your engine can stand anywhere from less than one second to perhaps minute of pinging before it suffers permanent and serious damage, depending on conditions.

The hotter your engine is, the more likely your engine is to ping. The farther your timing is advanced, the more likely your engine is to ping. The higher your compression ratio is, the more likely your engine is to ping. The lower the octane of gas you use, the more likely your engine is to ping.

So, in order to minimize the risk of pinging, do the following:

1. Make sure your engine doesn't over heat!
2. Make sure your timing is not too far advanced.
3. Make sure your compression ratio is not too high (< 7.5 to 1)
4. If necessary, use higher octane gas.

If you take care of the first three, you shouldn't have to worry about the last one"

Note: Newer engines like the Hemi have protection against it, but lower octane gas is never good... Also note that not all octanes are created equal. Some may be more 'watered down' ;-)
 

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Tornight, you are right about ping, my dad's Town Car pinged like a mother, higher octane cured it followed by new plugs and back to 87. My issue is the 300C manual specifically recommends a lower octane as an alternative and like any good politician avoids addressing a higher octane. Not that these guys are perfect, just look at the right pull, lack of locking rear seats or gas cap, erratic thermometer to name a few. There must be some reason they recommend a lower octane, your ping dissertation notwithstanding :) Until the C, I would have agreed that a lower octane is never good but the converse is not always true that a higher octane is always better with computer controls etc. Bottom line is I am sticking with 89 and won't use 93 unless the manual is updated like the emissions label recall for the plugs.
 

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Yup. Perzactly my take on the situation, II Kings.

I did however do a mixed tank of 91 and 87 at a station that didn't have a mid-grade. Guessed wrong and prolly ended up with close to 90 in the mix. But I don't think the octane is necessarily spot-on perfect anyway.
 

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IMO, if in doubt, always go to higher octane. I've seen lots of engine damage from "ping" and "knocking" especially with large, low revving V-8 engines. I am not aware of damage from too much octane.

Perhaps others can jump in here? I don't want to see people face major engine work under 100,000 miles and off-warranty, because they went to a low octane in a high performance car.
 

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I've been using 87 from name-brand stations and had no pinging. I'm at a low altitude and no problems in the hilly areas either. I've been to WOT - briefly.
 

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Newer engines have protection against ping, so you should never hear it unless something is truely toasted in there. The engine will automatically adjust timing to compensate for lower octane gas but at the very least, your losing performance. :(
 

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At higher altitude your effective compression ratio is decreasing due to the lack of density (thinning) of the air. Pinging would be less an issue as a result. However, your engine cooling system may strain to keep up with spirited acceleration because even though it is pressurized, the ambient environment is much lower pressure. the cooling system must maintain a steeper gradient. BUT, it should keep up (assuming it is in good shape, new cap, etc.). ad hoc ergo propter hoc (afterward therefore because of it) lower octaine gas at high altitudes like the mountains of Colorado is fine.
 

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Yes, my Sienna manual calls for 93 but does state 87 is OK but to expect reduced performance. This is not the case with the C, they call for a lower octane, since this is not the Gospel, are you guys thinking this is a misprint? It would be nice to have an answer as to why 93 is not recommended by DC. I fully agree with you guys on higher octane and I practice what I preach, but this Hemi with it's MDS calls for 89 0r 87 octane, these are the facts and they can not be disputed (unless DC changes the rec.) My 05 Odyssey on order with 3/6 cyl MDS calls for 87 only, 255hp, 250 torque.
 

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Tornnight said:
Newer engines have protection against ping, so you should never hear it unless something is truely toasted in there. The engine will automatically adjust timing to compensate for lower octane gas but at the very least, your losing performance. :(
Has anyone ever dyno'd the difference between 87 & 89?
 

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Here's even more information about gas and octane - and if you're REALLY techie/geeky, you can check out all the references this guy makes!

To find the octane discussion, look down about 1/3rd of the way from the top of the page for the heading, "6.13 Can higher octane fuels give me more power?"...

Here's the URL for this one:

http://www.faqs.org/faqs/autos/gasoline-faq/part3/
 
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