Jeep Garage  - Jeep Forum banner

87 or 89 Octane in Hemi?

14K views 44 replies 28 participants last post by  lll2for3lll 
#1 ·
I'm picking up my JGC Laredo X tonight, and I'm just curious what everybody fills up with? The manual suggests 89, but also says 87 is acceptable. Has anybody noticed a performance or mileage difference between the two? Any feedback is appreciated!
 
#3 ·
Yeah. I've never noticed any difference in mileage or performance with the Jeep or the 5.7 300C or Ram I used to have. They seem just as happy either way.
 
#5 ·
Higher octane will not give you any more gas mileage or HP. It is an anti-knock additive that is put in gas so the timing can advance without pre-ignition occuring. The timing will advance when a load is put on the engine, such as towing. I run 87 and have had no problems or lack of performance. I do plan on using 89 when I will be towing. Save your money, use 87 and splurge for the higher octane as needed.;)
 
#6 ·
Had both an '05 "C" and an "05 WK with Hemis. Always used 87 in both and had no performance problems whatsoever.
 
#10 ·
Although that suggests that your 87,89 octane equals 91,93 in Aus terms, which is still lower than i would ever use. I am assuming they must be tuned slightly differently, it looks like you guys cant really get what we call 98 Octane, which is 94 in US octane terms.
 
#13 ·
91 octane. With some cars, a little higher octane will get you a little more HP. Lower octane will work but the ECM will cut things back a bit. I have no idea if the same applies to my Hemi but I go for the 91 anyway. Maybe a waste but whatever. I have also read where sometimes you don't get a true 91 (or 89/87) so I feel like I'm hedging a bit.
 
#14 ·
91 octane. With some cars, a little higher octane will get you a little more HP. Lower octane will work but the ECM will cut things back a bit. I have no idea if the same applies to my Hemi but I go for the 91 anyway. Maybe a waste but whatever. I have also read where sometimes you don't get a true 91 (or 89/87) so I feel like I'm hedging a bit.

Actually octane is a anti-knock additive that does not increase HP or gas mileage.:cool:
 
#20 ·
I picked up our new overland on weds. and I can only assume that they filled it with 87 because I noticed a little lag at tip in with auto mode. i was down to about 1/4 tank today and topped off with 93 and there was an immediate change. The reply about the timing being retarded if lesser fuel is used is correct, I believe that is exactly what happened the HEMI is a relatively high compression engine at 10.5:1 and the lower flash point can affect timing.
 
#22 ·
I thought premium fuel shouldn't be used in the hemi? Anyone know?
It is tuned to produce maximum power with 89 octane. Anything over that is a waste of money. If you use 87 octane, the ECU will very slightly retard timing. My guess is that you will lose about 5 lb-ft.

What he may have noticed is the electronic throttle and transmission shift map adapting to his driving style after about 100 miles. It is covered in the Owner's manual.
 
#24 ·
A petroleum executive once told me 87 octane is a commodity in the oil industry meaning it could have been refined by any company anywhere. He advised I always go with brand name 89 or higher because it was refined to the exact standards of the folks with their name on the big sign at the gas station. 89+ when purchased from the big boys is the as-advertised stuff with detergents and whatever, assuming the retailer doesn't mess it up with sludge in their tanks or shady practices. This executive spent a career in his industry so maybe he drank too much of the cool aid but since I heard this I've stuck with 89 or higher.
 
#25 · (Edited)
A petroleum executive once told me 87 octane is a commodity in the oil industry meaning it could have been refined by any company anywhere. He advised I always go with brand name 89 or higher because it was refined to the exact standards of the folks with their name on the big sign at the gas station. 89+ when purchased from the big boys is the as-advertised stuff with detergents and whatever, assuming the retailer doesn't mess it up with sludge in their tanks or shady practices. This executive spent a career in his industry so maybe he drank too much of the cool aid but since I heard this I've stuck with 89 or higher.
Gas is shipped in pipelines to local distributers. Then they add different additives based on brand specs. Then that gas is delivered to local stations. The base gas is all the same at no name and brand name stations. The main difference is the additives that are added at the distributers. They don't ship different octane levels at the pipeline level of distrubition.:cool:

http://www.eia.gov/energyexplained/index.cfm?page=gasoline_where
 
#26 ·
Agreed...but the ethanol levels are different. Costco gas is cheaper as it has higher levels of ethanol. Both my mini dealer and Porsche dealers have signs that go through and that injector assemblies will fail if too much ethanol is used.

Just fyi
 
#27 ·
95 octane, but I assume Kuwait's octane rating is different. Dealership recommended 95. We get 91(i think it's 91), 95 and 98. (this is of course if I'm getting the numbers right but I know they're all above 90).
 
#29 ·
In reality, if the $3 per fillup is having you question whether or not to use the recommended octane or the minimum octane, you have bigger problems.

I use 89 in mine. I have tried 87 and it feels just fine without any power decrease but again, it's $3 per fill up to use the recommended octane.
 
#30 ·
I agree. I can be fiscally conservative but after spending $41k on a vehicle what's an extra $10-12 per month to use the recommended octane.

I suspect there will always be sides to this discussion. Do what is best for your situation. If 89 octane was the minimum required vs. recommended it would be stated in the manual and/or on the fuel door. My last vehicle required a minimum of 91 octane. Would the knock-sensors adjust for a lower value, yes, but with a reduction in fuel economy and power.
 
#33 ·
For the first 3000 km I used 89 octane, and recorded my overall mileage.
Then I switched down to 87 octane and again monitored my mileage.
I average just around 16.6 mpg with a combination of highway/city.

On the highway I'm getting 12.5 l/100 km or 19 mpg.
I didn't see any difference between the two octane levels except for a savings in my pocket.
Here in Canada gas is around 1.18 per litre for 87 octane and $1.28 litre for 89 octane. Thats a difference of 38 cents a gallon (or additional $7.00 every fill).
I have to fill the tank once a week.
So for me, it makes sense to use 87 octane, and just use 89 when I'm towing, or putting the engine under load conditions.
 
#37 ·
Done one plug change at 50,000km and sold it at 100,000km.
Cant answer that one, only done 20,000km on low octane fuel for 2 services.
 
#41 ·
But if you fill half a tank at a time you are not getting the full octane.
And the premium octane here is cleaner, cleaner oil at service. Cleaner better running engine.
 
#44 ·
Up here in Canada they have ethanol in 87 and 89 octanes and no ethanol in the premium so I run premium in my 5.7 GC. For the extra couple bucks per month to run the best in the best it's worth it to me. I also run it in my SRT Challenger. Always Shell and if no Shell stations around its Esso. Never 7-11 or Costco. Shell was proven to have highest amount of detergents in a boil off comparison test.
 
#45 ·
Yep. I prefer Shell.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top