fuel octane, new hemi

[donnyj08]

the 2012 hemi is recommended for 89, but 87 will work. ive used 91 from swifty the last few fills, because its 20 cents cheaper than the others. what octane do you hemi guys prefer? it runs good on the 91 stuff as far as i can tell. just not sure ill continue using their fuel, ive heard a lot of negative things about swifty. they sell a ton of fuel though. its always packed, because it is usually a penny or two cheaper and always waits a day or two to raise prices when the shells and others jump up $.25. but ive always wondered about the 89 octane, because it does not seem to be bought often. most people buy 87 or premium. what do you guys use in the hemi?

 

[JHZR2]

If 89 is recommended, Id run 89. If it is like my saab, which is designed to not advance further than what 90 octane will allow, there is no benefit.

 

[rg200amp]

Search the net for dyno tests.

VW calls for 87oct in my 2.5l, however, when using 91 dyno tests have shown an increase of about 5HP and 12TQ as well as a 1-2 mpg increase. . .


If you can't find any info, you may want to experiment. It may not be a benefit at all.

Following the car maker's recommendation is fine.

 

[Texan4Life]

I have always run 87 with no problems.

 

[RamFan]

Run the 89 and call it a day.

 

[Topo]

I don't think it will be a big issue to run 87 octane, with knock sensors you won't have spark knock and it will adjust timing properly. My Dad has run his for 80,000 miles with regular gas. In addition, they are a big truck, with truck gas mileage(low). Cost would usually be 10 cents per gallon more for unleaded & mid-grade and you probably will not see a huge mileage swing between the two. Perhaps under a load, you get better performance ( increase horsepower)using the correct octane and would see a bigger benefit. Under normal driving conditions It's doubtful you see much improvement in performance and mileage. I have not seen any difference in mileage on my car, recommended octane is mid-grade. All you can do is test the theory, either way you truck will run fine with regular, mid-grade or premium.

 

[SteveSRT8]

Your octane spec is just like your oil spec. It is designed to protect you in the WORST case scenario.

Modern Hemis run great on any octane, and they have very sensitive and accurate knock sensors to prevent damage.

My car is spec'd for premium fuel and has had a tank or two of 87 and you could scarcely tell the difference in normal driving.

 

[mechtech2]

Yes, it will run with lower octane fuel.
But why outsmart the computer programming?
That car needs 89 or even a bit more.
It is best to use it for bunches of reasons.
You have to feed it's habit!