Engine Knocking - 6.4L / Octane ratings

Discussion in 'Challenger Mechanical Problems Forum | TSB's' started by GoFast, Nov 25, 2019.

  1. GoFast

    GoFast Member

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    I got my 2018 Scat Pack (Automatic, with just under 20K miles) a few weeks ago and in the first few days I noticed that the engine was knocking. I figured the dealer put in regular gas so on the next fill up I made sure to put in 91... still knocking. Added STP octane booster and it got much quieter. Now it sounds like a ticking. I'm wondering if the ticking is something different. Here are 2 possible conclusions I am working on.



    Hypotheses #1 - The 6.4L runs better in the 93-96 octane range than it does in the 91 range and even thought it's 91+ most gas stations are closer, if not under, 91.

    Anyone know which gas stations are better for higher octane? I live in California, near Oakland, in the San Francisco Bay Area and there are not any 93+ octane gas station nearby (all are 87, 89, 91). I would rather not have to use an octane booster every time I fill up but I also don't want my engine to knock. Does anyone use the higher octane bottles, like the race gas number (96, 101, etc.)? I'm wondering if I can buy a bottle of 101 and just use half or 1/3 each time since it's around the same cost as the STP. I admit, as much as I am a DIY mechanic and have been working on my own cars for over 20 years (plus Auto shop in High School and College), I'm not very well versed in how the octane boosters work. Will adding a full bottle of 101 be bad for the car or a waist?



    Hypotheses #2 - The ticking I'm hearing is because of the oil the dealer used and not related to the knocking from the 91 octane gas. The 6.4L doesn't like the dealer oil and something like Mobile 1 Synthetic would be better.

    What oil is everyone using in their 392 engines? I used Mobile 1 Synth in previous vehicles and was going to do the same on my next oil change but if it will stop the ticking I might do it sooner.



    Anyone else have similar experiences with their 6.4L engines ticking or knocking? Do these engines just tick all the time? My understanding of car engines is that they should not, but I don't have experience with HEMI engines and heard somewhere someone mention the "HEMI Tick".
     
  2. Alan Johnston

    Alan Johnston Member

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    My 5.7 L. engine ticks sometimes when I start when its cold. I figure it's just the thin oil draining out of the lifters and the ticking it goes away. I don't have any knocking with this car. I use 89 octane always.
     
  3. Josh82

    Josh82 Member

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    I have a 2013 challenger rt with the 5.7 but I have a 6 speed so I have to use the higher octane and I have the tick but it's louder some days than others so I don't know if it's a lifter or an injector I recently changed the plugs I'm afraid to take it in and have it diagnosed because if they tell me the engine is junk I will probably cry lol
     
  4. SRT-Tom

    SRT-Tom Full Access Member Article Writer

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    I use Valero 93 octane (a top tier gas) in my 2009 SRT and it runs great.

    [​IMG]
     
  5. B5blueRT

    B5blueRT Full Access Member

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    I've run the upper tier gasolines (mainly Shell) 87, 89, 91 and 93 octane in my 2015 R/T - 5.7L. A8 with 9,000 miles. Also went to full synthetic oil, no difference, still have the tick. To fix it, I think I'll go with a Flowmaster American Thunder cat back exhaust in the spring so I don't hear the tick anymore. :):)
     
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  6. IntimidatorRT

    IntimidatorRT Well-Known Member Staff Member Super Moderator

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    been running Murphy's gas in mine 93 oct. and no problems here, have over 102,000 miles on mine
     
  7. baccaruda

    baccaruda Active Member

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    BP 93 octane and Mobil 1 all since day one .
     
  8. Jelli79

    Jelli79 Member

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    91 Octane should be fine to not cause a ping, i would change the oil out, it's cheap and then you can rule it out, use a quality filter like the SRT filter and a good synthetic oil, low octane gas can cause a ping sound but shouldn't cause a knock per say
     
  9. Josh82

    Josh82 Member

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    I use mobil one full synthetic and a wix oil filter I put 6 quarts of Mobil one and a quart of Lucas oil stabilizer and I still have a tick
     
  10. Cynthia

    Cynthia Member

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    Welcome to the Hemi Tick!
    You can make it quite, but it doesn't go away. I am on my 3rd vehicle with a Hemi 5.7. They all tick/ticked. My current is a 2017 T/A Challenger. I run top tier Shell in it with Castrol Edge full synthetic oil and a Wix XP filter. I also add VIP Octane Boost.