[WallyRT]

ive read a couple posts about this but still havent answered clearly my question. On the vehicle manual it says ( for manual transmissions ) that 91 octane is recommended. But i live in North Carolina where the gas options at gas stations are 87, 89, 93. So which should i use? the 89 or the 93 since 91 is not available. Also as many of you know. Gas stations are adding ethanol into the gas to make it cheaper i guess. Is that even safe for my challenger? i have a friend with the same exact vehicle and he always argues that 87 octane runs fine.

 

[teddyp]

I can't give you a scientific or engineering perspective, however I'd go with the closest higher. In your case 93. I know guys are going to say the manual reads "recommended" which isn't telling you "must" or "only". But since I only put about 5000 miles a year on this car, it wouldn't bother me. I have a 392 so it calls for super. My .02 cents.

 

[wasp392]

Yep, put 93 oct and if you can find ethanol free gas, even better.


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[Slidd]

I think the 91 M6 requirement from Dodge is just protection against someone who can't drive and lugs the engine. It's the same tune as the automatic and they recommend 89 for it or maybe even 87 for 2015. I have run both 89 and 87 in my M6 with no issues and no change in performance or economy.

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[Yahooligan]

I think the 91 M6 requirement from Dodge is just protection against someone who can't drive and lugs the engine. It's the same tune as the automatic and they recommend 89 for it or maybe even 87 for 2015. I have run both 89 and 87 in my M6 with no issues and no change in performance or economy.

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If it's the same tune then why is the manual listed with more HP and torque than the auto? It's not the same and for me it was the opposite, I could tell when my wife forgot to put 91 in when the 2011 was still new to us. 91 won't protect the engine from a bad driver.

 

[Rich1559]

I used 87 in my 12 R/T 6M the entire time I owned it (3 years). I never had any issue.

 

[A knight]

Why would they change the tune with the manual?

 

[Yahooligan]

Why would they change the tune with the manual?

Why would they change the tune for the auto so that it's making less power than the stick?

 

[teddyp]

Way off subject here, but I'm sure the tune must be different simply because one motor has MDS and the other doesn't.

 

[A knight]

Way off subject here, but I'm sure the tune must be different simply because one motor has MDS and the other doesn't.

Well if that's the case then why are both the auto and manual 392 rated the same?

 

[Slidd]

If it's the same tune then why is the manual listed with more HP and torque than the auto? It's not the same and for me it was the opposite, I could tell when my wife forgot to put 91 in when the 2011 was still new to us. 91 won't protect the engine from a bad driver.

3 hp more due to the larger 2.5 inch exhaust and better mufflers on the M6.

And with the lugging maybe not totally protect the engine but will definitely reduce detonation potential when someone refuses to downshift and lugs the engine, the automatic has no such concern as it will downshift by itself.

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[Yahooligan]

3 hp more due to the larger 2.5 inch exhaust and better mufflers on the M6.

And with the lugging maybe not totally protect the engine but will definitely reduce detonation potential when someone refuses to downshift and lugs the engine, the automatic has no such concern as it will downshift by itself.

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The engine is perfectly capable of protecting itself, that's what the knock sensor is for. I think you're really reaching here.

Combine that with the auto folks that run a canned 91 tune and experience a decent improvement in power and the manual folks that don't because the canned 91 tune is nearly identical to the factory 91 tune.

 

[teddyp]

Well if that's the case then why are both the auto and manual 392 rated the same?

In the RTs they aren't, not sure why 392s are. 6.4 is newer so maybe it incorporates newer tech?

 

[BlackHemi41]

I'm not sure the 5.7 factory hp ratings tell the whole story. When they went to electro-hydraulic steering in 2011, theoretically that should have freed up a few hp due to less drag on the engine, but it stayed at 372 or 376. Meanwhile the Ram 1500 went from 390 to 395 hp when it switched to electric steering in 2013, and that was the reason for it. I do believe the 4hp would be due to the less restrictive bottle mufflers on the 6 speed, but I also believe the ratings aren't entirely accurate and the theories that it was under rated to protect the 6.1 425 hp could be true, although I can't prove it. The Ram 395hp is on recommended 89 octane, so I don't think 376 hp on the 6 speed is due to a 91 octane tune. Rating the Challenger 5.7 at 390 hp back in '09 would have certainly made a 425 hp SRT seem less worth the money.

 

[Yahooligan]

The peak HP and torque with the manuals are at different RPMs than the auto, it's not more peak HP at the same RPMs so I don't think it's just freeing up power.

The peaks also don't tell the whole story, the manual could very well have more power across the board, but the only numbers published are the peaks.

 

[DJ Hemi]

If you wish to follow the manufacturer's recommendation for octane, and if 91 octane is not available in your area, you must go with 93. 87 octane does not cut it if you wish to follow the recommendation.

If you do not care about the recommendation, run whatever octane you wish.

 

[A knight]

The horsepower gain from switching to electric steering is not enough to cause any serious difference in power. A hydraulic power steering pump on these cars takes 1-2 hp max to run. Switching to electric is more to change the feel of the steering, not to free up power.