hello everybody,

i have a question about the hemi.... is it okay to use the octane 87 on the hemi all the times than the normal gas rating (89)? Will the octane 87 damage anything inside or decrease mpg or something? Give me more info if you know anything. Any help or advices would be greatly appreciated.

Thanks

 

I use 87 all the time even in the 105*+ heat here...I haven't noticed any knock or performance loss since switching from 91. I didn't just switch though...I looked up the compression which is 9.6 and not high at all. I also noticed on all the rams i've seen is a lot of soot in the tail pipe...which shows the truck is running a little rich fromt he factory tuneand that helps prevent detonation also.

That's being pretty stock though...if you get a canned tune you'll need the higher octane due to timing advance and leaning out.

 

if the gas is running too lean through the exhaust, the o2 sensor will sense if it run too lean then it will dump more gas into the engine which will result loss in mpg... that is what i am worried about.. i am always running it on 89 which is very good on the engine..

 

I use 89 in my hemi, i tried using 87, and I saw my MPG go down, plus the manual said to use 89 in the hemi. I mix 87 & 89, but never a full tank of 87. I don't think think that it will damage anything, I just noticed a drop in MPG. My $.02

 

I haven't noticed a drop in mpg and I don't see why the mpg would drop...octane is just the fuels resistance to burning. Once the plug fires 87 will burn just like 89...to each his own.

 

Possibly it is causing the PCM to back off the timing a little to prevent detonation thus the little loss in power will also make the MPG drop.
Mine has increased since I switched to 89. Went up from 14.5 to 15.4 driving the same way.

 

^^^That's possible if the rams can "sense" the lower octane like some GM's do and have a seperate fuel/timing table. But again I haven't noticed a drop in either mpg or power...the drop in performancewas huge and completely noticablewhen I tried 87 for afew tanksin my LS1. But if you want to be safe then stay with 89+...it's only a few bucks more a tank so it's not a big deal.

If I thought it was neededI would use it too trust me....I take very good care of my vehicles and wash the engine bay every oil change. A clean engine is a happy engine ..hahha

 

THen i should keep using the 89 to keep my mileage constant and not lose any mpg.... thanks for the help

 

If the 87 in your area has 10% Ethanol, chancesare it is already at 89 octane or better.

 

I use 87 all the time. I occasionally put some 89 in butwhen I do my mileage goes down. Maybe different engines react differently to the octane change. I don't tow anything or carry heavy loads so my engine is not under stress. To each his own, for me it's 87.



Rick