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5.7 Hemi - 87 or 89 Octane

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RSConsulting

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Haven't found an answer in the forum search.

Owners manual recommends 89 Octane, but says that 87 Octane is okay also.

Aside from a (potential) slight increase in performance, and possibly MPG - is there any DETRIMENTAL EFFECT to just sticking with 87?

Regards,

Rick
 
There is a pretty sizable thread on this, but essentially if you want the best engine performance and fuel economy you should go with 89 octane, but 87 is acceptable to use instead without an negatives effects (mechanically) to the engine. However the fuel economy you lose probably isn't worth the cost difference.

But quite a few people swear by 87 octane exclusively, many claiming they don't notice a difference in performance or fuel economy vs 89. I personally use 91 octane because I go to Costco and they only offer 87 or 91 and Costco 91 is actually cheaper than other stations 87 octane while being top tier rated fuel.
 
I'm sure you've probably considered it, but when I fill up at Costco, I blend the 91 with the 87 to get to 89, or close to it. Saves some $ and really no additional benefit to using all 91 that I am aware of.
 
My 2005 manual says the same thing. I've been using 87 octane in my '05 since new, and it still runs great.
 
i pretty much ran 87 for the first year ~11,000 miles. averaged mid 16 MPG.
recently BUC-EE'S opened close to my house just across the Alabama state line and fuel there is almost $0.30 cheaper than anywhere here. so for the price of 87 i have been buying 89. performance has felt a bit better and fuel economy has bumped right at 2 MPG's city driving.
 
Ranger482 said:
I'm sure you've probably considered it, but when I fill up at Costco, I blend the 91 with the 87 to get to 89, or close to it. Saves some $ and really no additional benefit to using all 91 that I am aware of.
Click to expand...

I did consider doing that, filling up with 87 at half tank. But sometimes I get lazy and on my 91 tank I get down to 1/4 and it's too late to mix right. I considered doing it at the pump as well, but with the size of the line and everyone watching to make sure you aren't taking too much time, that's a no-go :)
 
If 2mpg is realistic, the the premium is likely a good option on a regular basis. At Seattle gas prices I'm hovering at $.20 a mile driving. Costco premium is usually only .10 to .30 more per gallon.
 
Goatmann said:
i pretty much ran 87 for the first year ~11,000 miles. averaged mid 16 MPG.
recently BUC-EE'S opened close to my house just across the Alabama state line and fuel there is almost $0.30 cheaper than anywhere here. so for the price of 87 i have been buying 89. performance has felt a bit better and fuel economy has bumped right at 2 MPG's city driving.
Click to expand...
Interesting!....Off topic but that Buc-ees is huge!!! Im originally from up north so ive never see one until we stopped there lol
 
I sware by 89 for mine (91 for the Durango R/T).
everyone else is like BS and all that .. I've driven the new rig with 87 / 87+eth / 89+eth (available mixtures in my area) .. and although 89 has Ethanol mix, it gives a better snap off the line, better gas mileage for my day-to-day driving, and faster ETs (0-30 & 0-60) .. I only have 800 miles on the engine, so I know I'll see better mileage after everything is broken in and re-learned to my habits. (see my posts in the 0-30 & 0-60 thread - I run the tank down to less than 75 miles est. left then fill, then drive it for at least 1/4 tank before using my TAZER DT for testing). Once I get the RAMAIR installed, I'll talk with my local tuner and do some proper testing on the Dyno.

PS: RAM/FCA don't care about MPG -- they want you to spend money on carbon fuels -- what they care about is getting you better emissions so they don't pay fines. :)

parnine said:
No way 89 gives an extra 2mpg city (or hwy) .....
Click to expand...

I had my Durango R/T for 36 months. I ran 87 & 91 to/from Omaha, NE to Chicago, IL (500 miles) .. I got over 50 miles out of the tanks extra running 91 (with SPORT mode disabled). I'm not going to run the calculator for the mpg gains for you, I just know it was worth it to me to run 91 in that. I'm doing my own testing in the RAM to see if it has any similar mpg gains/loses as it learns my drive routine.
 
Diamondback said:
I sware by 89 for mine (91 for the Durango R/T).
everyone else is like BS and all that .. I've driven the new rig with 87 / 87+eth / 89+eth (available mixtures in my area) .. and although 89 has Ethanol mix, it gives a better snap off the line, better gas mileage for my day-to-day driving, and faster ETs (0-30 & 0-60) .. I only have 800 miles on the engine, so I know I'll see better mileage after everything is broken in and re-learned to my habits. (see my posts in the 0-30 & 0-60 thread - I run the tank down to less than 75 miles est. left then fill, then drive it for at least 1/4 tank before using my TAZER DT for testing). Once I get the RAMAIR installed, I'll talk with my local tuner and do some proper testing on the Dyno.

PS: RAM/FCA don't care about MPG -- they want you to spend money on carbon fuels -- what they care about is getting you better emissions so they don't pay fines. :)



I had my Durango R/T for 36 months. I ran 87 & 91 to/from Omaha, NE to Chicago, IL (500 miles) .. I got over 50 miles out of the tanks extra running 91 (with SPORT mode disabled). I'm not going to run the calculator for the mpg gains for you, I just know it was worth it to me to run 91 in that. I'm doing my own testing in the RAM to see if it has any similar mpg gains/loses as it learns my drive routine.
Click to expand...

Now you are going from 87 to 91, when original was 87 to 89 so changing parameters, but even then ..... best to you.

Curious though, with only 800 miles how many tanks have you had to do all this comparison ("..driven the new rig with 87 / 87+eth / 89+eth (available mixtures in my area) .. and although 89 has Ethanol mix, it gives a better snap off the line, better gas mileage for my day-to-day driving, and faster ETs (0-30 & 0-60) .. I only have 800 miles on the engine,..")?

For all others, be cautious with going from 87-89 and thinking it will give you 2mpg all 'things being 100% equal'
 
parnine said:
Now you are going from 87 to 91, when original was 87 to 89 so changing parameters, but even then ..... best to you.
Click to expand...
Nope that was for the Durango, not the 1500

parnine said:
Curious though, with only 800 miles how many tanks have you had to do all this comparison ("..driven the new rig with 87 / 87+eth / 89+eth (available mixtures in my area) .. and although 89 has Ethanol mix, it gives a better snap off the line, better gas mileage for my day-to-day driving, and faster ETs (0-30 & 0-60) .. I only have 800 miles on the engine,..")?

For all others, be cautious with going from 87-89 and thinking it will give you 2mpg all 'things being 100% equal'
Click to expand...

4 tanks .. 2 89+ .. 1 87+ .. and recently the 87 no-ETH.
 
Recently did two trips, approx 1800 miles each. Was running 85 most of it (NV, UT, ID) and noticed absolutely no difference power or mileage wise from 87.
 
I usually do 89, but the gas station attendants hear 87.

Thanks Muhammad, I mean, did save me a few bucks there, but that's why I just jump out and fill it myself
 
Rob5589 said:
Nope. I buy a 36k truck and use 85. Was there a point you were attempting to make?
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To save a few cents on 85 over 87 just doesn't make a lot of sense to me, and I am sure several others will agree. Do you HAVE to use 89? We know the answer is no, although it is highly recommended. However, to use 85 just sounds like it's penny wise and dollar foolish...that's my point as we don't know the long term impact of pi$$ poor octane fuel...your truck and do as you wish ;)
 
Nah, few tank fulls won't cause a thing. Wasn't even about saving money, it just happened to be the handle I kept grabbing. The original point I was making was, even with 85, there was no power or mpg loss. Actually, it hit 21.2 which is the best it has ever gotten, and that was driving 75-80. Hard to complain about that. Now back in CA, so 87 is what I will be using.
 
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