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RTFM
Sorry couldn’t help it
Do you have an auto or manual? Not that it’d make a difference on the 392s. You might wanna add it to your profile.
 

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I traded in my RT Plus for a Scat, can I use regular unleaded if I am not beating on the car?
Don't - you're running 10.9:1 compression ratio - 91 octane is just tolerated by the 392 in warm weather.

Detonation (spark knock) will cause serious damage.
 

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All we have is 93 in my area. I drive it til it gets to 1/2 full and fill it with 93 then it gets to 1/2 again then I fill it with with 89 and keep switching at a half a tank....JB.
 

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I traded in my RT Plus for a Scat, can I use regular unleaded if I am not beating on the car?
While I am not advocating you do this beating on the car can have the engine managing with a lower octane of gasoline. How you might ask? By the fact that by "beating" on the car you are using much more throttle and if enough throttle the DME can go open loop mode and enrichen the mixture which helps control detonation.

But the drive home can have the engine experiencing detonation. How you might ask? Because at low speed/low RPM operation the cylinder filling is quite good -- due to low engine speed coupled with a relatively large throttle opening which lowers pumping losses for one thing -- and as a result of this good cylinder filling combustion chamber pressure and temperature are pretty high.

You can see how at low speed/low RPM operation the instantaneous gas mileage goes up. In my GTO with its 6.0l 400hp V8 in 6th gear with engine RPMs just above idle I've seen 35mpg. I've also seen big timing advances sometimes over 30 degs. BTDC.

Under similar conditions I've seen really impressive mpg numbers from my Challenger though because the engine is not yet broken in I really try to avoid operating the engine in this fashion.

My advice regarding fuel is use the grade of octane the auto maker recommends, if at all possible, but in any case use the highest grade of octane you can find. (I guess I had better add that if the engine is spec'd to run 87 octane there is no real benefit to running a higher octane grade. The engine controller can't adjust timing to take advantage of the higher octane gasoline so the higher octane gasoline is for naught.)

In some areas 91 is all one can find so engines that call for 93 octane are SOL. But every automaker I know oks the use of 91 octane or even 90 octane (at least at higher elevations) in these cases.

No experience with my Challenger yet but I can tell you the time I had a chance to run 93 octane gasoline in my Porsche 996 Turbo -- which calls for 93 octane -- the engine transformation with 93 octane was remarkable. The engine really came "alive" with 93 octane gasoline. I kind of expect the Challenger to react similarly.
 

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Geeze, the OP buys a high performance car then wants to detune it by using low octane fuel! I suppose you can use 87 octane, the 392 has knock sensors and should retard the timing enough so as not to cause detonation damage, but performance will be severely curtailed. Might as well have kept the old R/T!



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Geeze, the OP buys a high performance car then wants to detune it by using low octane fuel! I suppose you can use 87 octane, the 392 has knock sensors and should retard the timing enough so as not to cause detonation damage, but performance will be severely curtailed. Might as well have kept the old R/T!



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There was a thread from a poster in UAE - they use RON ratings for octane - he was using the equivalent of 87 octane and detonation destroyed the ring lands on one bank of the engine - multiple cylinders. Twice.
Shop did a rebuild, and when the 2nd occurrence took place, they posted on CT and found out why - they thought it was valve / piston interference - but only took place on one bank. When

They thought the 91 octane called for in owners manual corresponded to their fuel ratings system. In North / South America we use RON + MON /2 which is the averaged number of the two. Our figures for octane produce a lower number than the RON method used abroad:

they'll have 93 / 95 / 98 and sometime 100 octane in Europe / Asia / Far East markets with their rating system
 

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Use diesel, that'll solve the problem! LOL
Our goofy laws in Oregon (been effect since 1951):

The general public is not allowed to dispense gasoline or handle any
gasoline dispensing equipment at retail facilities, with two exceptions:
The first exception is to allow pilots to dispense aviation fuel at airports
permitted by the Department of Aviation.


Upon request of a motorcyclist, the attendant shall set the fuel dispensing device and hand the nozzle to the motorcyclist, who may then dispense fuel into their motorcycle.
Upon completion, the motorcyclist shall hand the nozzle back to the attendant, who shall deactivate the dispenser and replace the nozzle


and several times in a day - they'll pump gasoline into a Diesel fueled vehicle...happens somewhere throughout the state.

Our "skilled fuel dispensing technicians" at work...
 

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I know someone that uses 87 from day 1 of picking up his 392 Scat. I'll let you know if it blows up or not.
 

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I let my R/T 5.7 6 speed get down to 1/4 tank. Then I put in 10 gals 93 octane and 5 gals 87 octane which equals 91 octane. Works great, and simple to do. Always put the 10 gals 93 first, if it doesn't take the full 5 gals 87 so be it, a little higher than 91 octane. ☺
 

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I know someone that uses 87 from day 1 of picking up his 392 Scat. I'll let you know if it blows up or not.
When a ring land lets go, he'll get a misfire code in a cylinder - by the time its discovered what the cause is - there' significant damage. That's what ongoing detonation will do.

That engine is probably going to carbon up more as well since its pulling timing a much as it can to rein in detonation (spark knock).
 

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too bad for whoever buys the car after his lease is over
 

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I know someone that uses 87 from day 1 of picking up his 392 Scat. I'll let you know if it blows up or not.
The problem is the engine seldom blows up from this abuse.

There a number of negatives to running a grade of octane below the auto maker's recommendations.

Running costs, fuel costs, are higher because the engine is less efficient with 87 octane gasoline -- which is 4 octane points below the 91 Dodge recommends. While the 87 octane gasoline is less expensive the engine may require more of it. Thus the "savings" is not nearly as good as the price per gallon difference suggests.

With too low an octane to keep combustion pressure down to avoid detonation the engine controller delays spark. This results in the burning of the mixture occuring later in the piston's power stroke. Less pressure is created -- which controls detonation -- but the chemical energy in the gasoline is wasted.

The best example I can offer is when one is riding a bicycle. One inherently "knows" the proper time to apply downforce to the pedal to get maximize benefit from his expenditure of energy to propel the bicycle. If one can force himself to delay applying downforce he can feel that he is "chasing" the pedal down.

This is essentially what is occuring in the engine. The delayed combustion is chasing the piston down the cylinder exerting less force than it would had combustion been started at the optimum time.

The burning of the fuel still produces the same amount of BTU's though regardless if the spark is delayed or not. But rather than these BTU's increasing the combustion pressure more of them just get wasted. The delayed combustion resuts in mixture burning that continues long past when combustion triggered earlier begins to substantially taper off. The result is all exposed surfaces/components get subjected to higher exhaust gas temperatures. Pistons, ring lands, compression rings, intake valves -- which are closed so are affected little by this -- and exhaust valves. Exhaust valves are closed to of course but are heated by the combustion process. Then they open and get further heated by the exhaust gases flowing past. Thus the exhaust valves experience a higher than normal operating temperature. All the time. Not good.

O2 sensors and exhaust converters also experience higher exhaust gas temperatures and extra heat shortens their service life.

Using the wrong/too low octane gasoline in a high performance engine is just plain wrong. That no immediate symptoms or issues or problems appear doesn't mean it is not wrong.
 

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yeah, he's aware. he doesn't care though. "next guy's problem" he says.
 

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i asked him to keep me updated, because i'm curious to see what will happen.
 

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Geeze, the OP buys a high performance car then wants to detune it by using low octane fuel! I suppose you can use 87 octane, the 392 has knock sensors and should retard the timing enough so as not to cause detonation damage, but performance will be severely curtailed. Might as well have kept the old R/T!



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DITTO! These are NOT budget cars. It is a 12 second race car............ truly get a Civic and put a hole in the exhaust and put a stripe on it. :notallthere:
 
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