100 Octane vs 91 Octane

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mbacfp

mbacfp

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Hello All,

Hope everyone is doing well. I have a question regarding my Dodge Hellcat Charger...book says minimum Octane 91. Would occasionally filling up with 100 Octane race fuel be good for the car periodically? Don't plan on racing it...just curious if it is good for the powertrain or would I be wasting my money? As always, appreciate all the advice.
 
Octane is not how powerful (how much energy) the gas is. It is how much you can compress it before it would self detonate. Your engine compresses at a specific amount (ratio) that requires at least 91 Octane (ie so the gas does not explode before the spark plug fires)

Now the more you can compress the air/fuel the more power you can get get.. it would require modding your car..

in short you are wasting your money.
 
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Ok, so to take advantage of 100 Octane...car would have to be modded to benefit from it.
 
Octane has nothing to do with cleaner burning either. It's purely resistance to pre-ignition from higher compression.
 
100 Octane will give no benefit even if modded... if the engine doesn't need the additional octane to prevent spark knock at maximum programmed spark advance.

Long story short: 100 octane is highly unlikely to help anything in your situation... but it smells oh so much better than pump gas. Not quite sure what compound it is, but combusted "race" gas just smells like the finest perfume to my nose
smile.gif
 
Thanks everyone. I will save my money for the extra insurance premiums due to this car...ha...appreciate it.
 
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I would get some form of logging device so you can measure max spark advance and log your advance with 91 pump fuel and then log with 100 octane race fuel. I'd almost bet money you'll see some increase in timing and therefore performance. Its a 700+HP supercharged car, you [censored] right it will run better with 100 octane race fuel, even if its only due to the consistency and purity of the race fuel!

If I owned a HellCat you can bet it would see some track fun and for engine protection I'd run the best oil and fuel I could get! Pump fuel, especially the garbage you have there on the west coast is marginal at best and never consistent. Race fuel is VERY consistent and guaranteed to be be at least the min octane number its rated at.
 
Originally Posted By: racin4ds
I would get some form of logging device so you can measure max spark advance and log your advance with 91 pump fuel and then log with 100 octane race fuel. I'd almost bet money you'll see some increase in timing and therefore performance. Its a 700+HP supercharged car, you [censored] right it will run better with 100 octane race fuel, even if its only due to the consistency and purity of the race fuel!

If I owned a HellCat you can bet it would see some track fun and for engine protection I'd run the best oil and fuel I could get! Pump fuel, especially the garbage you have there on the west coast is marginal at best and never consistent. Race fuel is VERY consistent and guaranteed to be be at least the min octane number its rated at.

I did not imagine that cars can time it for better than suggested octane. [censored] cat is a special case.
if it can it would produce more horses. But i would not bet on it. Also there is OBD dongle with app that see timing as well as "time" your 0-60mph.. would be interesting to see the difference..
 
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Thanks. says 91+ Octane in the owners manual. If it didn't make a difference then why do they put + in the book. CA has horrible options...wish we had 93 octane. Drives great on 91 just was curious if 100 would be healthy for it. I know nothing about this hence why I am here. I guess I can try 100 and give my seat of the pants experience. 100 Octane is 14 miles away from me at a 76 station...I want to say it is $7.xx or so a gallon...kind of pricey. Take care all.
 
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I just checked some hellcat forums and they say it is useless without a tune. The demon however has a button to press for that 100 octane gas. I would save your money. how much is insurance on that?
 
Originally Posted By: mbacfp
Thanks. says 91+ Octane in the owners manual. If it didn't make a difference then why do they put + in the book. CA has horrible options...wish we had 93 octane. Drives great on 91 just was curious if 100 would be healthy for it. I know nothing about this hence why I am here. I guess I can try 100 and give my seat of the pants experience. 100 Octane is 14 miles away from me at a 76 station...I want to say it is $7.xx or so a gallon...kind of pricey. Take care all.


Octane is just the ability to resist detonation at higher compression ratios. The BTU content of 91 and 100 would be the same so the energy content of 100 octane is the same as 91. They say 91+ because 91 is common on the west coast and 93 is common on the east coast.
 
1. Cali premium is not as good as elsewhere in the country. CobbTuning makes dedicated, LOWER-powered tunes for Arizona, California, and Nevada. They offer:

93 AKI
91AKI
91AKI (ACN)

2. We have no way of knowing if Cali 91 is good enough, without data. Power-robbing feedback (instantaneously) and learned (in ECU memory, based on multiple knock events at a specific load and RPM) knock is very quickly handled by the ECU, before it would be audible to you. That is, unless you got a bad tank of gas or went for, 100% premium to 87 AKI and the left the gas station at WOT, up a steep hill.

3. Some knock is normal and harmless, so long as you’re not too far off from he design max timing/fueling map. The further you get away from ideal, the more noticeable the reaction of the ECU (e.g., stuttering, loss or dips in power at certain RPM/load, actual, audible knock or pinging.)

An easy thing to do is add 25% of your tank volume of 100 octane, reset your ECU, and see you if there’s any difference. If it’s close, you may notice a much larger difference when you next fill up with 100% 91 octane and then drive WITHOUT resetting the ECU. Your ECU will then have to react quickly if it needs to pull timing.
 
Spending $60,000.00 on a ca and not willing to try the racing gas [if unleaded] seem un hot rodder like. I love the car I bought a 2015 Ford F150 and the dealer had a green Challenger Hellcat and I offered to write a check right now if would give me the same deal he did on the p/u. He said no but I am enjoying the P/U. They are nice cars and enjoy the ride.
 
Originally Posted By: dave1251
No benefit. If you want to spend that kind of money. Send it to me and I give you some "Racing Fuel".


How could you possibly know this???
 
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