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After one of the hurricanes around here, it was weeks before you could find premium.


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From a few days before Irma, till a week or so after, all you could get here was premium.
 

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The regular vs. premium gas debate is always a lively one. I probably should pop some popcorn and enjoy the entertainment. 馃お

In my opinion.... When I put the right foot on the floor, I want to be confident I have provided my vehicle with everything it needs to perform the way I expect. I run premium in everything, always have, always will. I just sold & replaced our two daily drivers. One at 311k, the other at 328k on their original motors, never rebuilt. Granted regular maintenance is a big part of that longevity too. The bottom line is I believe I will get out of my vehicles what I put in to them, and a diet of premium fuel is one part of that.

Your opinion will likely be different. I will respect it, but you won't change my mind.
Running premium in a vehicle that calls for regular will have no benefit, in fact can cause the vehicle to run worse. Higher octane gas resists ignition more than lower octane gas and therefore can have an effect similar to retarded ignition timing.
 

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There's a Costco about 11 miles from me & I paid $2.38/gal for 93 octane about a week ago. At the time, the cheapest TopTier by me was typically $3.09. That's a difference of 71 cents per gallon. I happened to be out that way & filled up with over 17 gallons. That's a $12 savings compared to other TopTier. Sometimes it's worth the ride out there just to get gas. That Costco always has the cheapest premium by a significant amount, even compared to other Costcos in the area.
 

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The other day I accidently refilled the tank on the SC with 87. I was very worried and my first thought was to siphon it out and put it into the Expedition. But then I had a thought and went to Autozone and put in some octane booster. Crisis averted.
More like bullet dodged. (No pun...)

Chances are the octane booster you bought and used only raised the octane rating by a few *tenths" of one point. IOWs, you raised the octane from 87 to 87.2.

Octane boosters that bring the octane up by whole numbers are expensive and not street legal.

They'll run on anything in an emergency, somebody just ran thru a tank of E85 on a Hellcat and no issue.


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Recall that thread. While apparently the engine ran and without any untoward behavior I would not rely upon that guy's good luck and attempt to run E85 in my Hellcat or any car/engine not specifically designed for its use.

The regular vs. premium gas debate is always a lively one. I probably should pop some popcorn and enjoy the entertainment. 馃お

In my opinion.... When I put the right foot on the floor, I want to be confident I have provided my vehicle with everything it needs to perform the way I expect. I run premium in everything, always have, always will. I just sold & replaced our two daily drivers. One at 311k, the other at 328k on their original motors, never rebuilt. Granted regular maintenance is a big part of that longevity too. The bottom line is I believe I will get out of my vehicles what I put in to them, and a diet of premium fuel is one part of that.

Your opinion will likely be different. I will respect it, but you won't change my mind.
Under hard acceleration the engine controller is free to fuel the engine for maximum power. It riches up the mixture which helps keep detonation under control. Also the richer mixture appears to require less ignition advance. And because the engine speed is fairly high cylinder filling is not as good as one might believe (some of the power comes from fact the engine is running at a higher RPM) this tends to reduce the pressure in the combustion chamber.

'course, I'm not advocating one fill up with 87 if he's going to be driving on the track using full throttle all the time.

The octane of a gasoline is important at other times, not only those times one is hard on the throttle.

For instance at part throttle low engine speed operation cylinder filling is very good and the pressure generated in the combustion chamber is very high. With the proper grade of gasoline the engine timing will be quite advanced.

With my 2006 GTO and operating the car in this fashion I observed around 35 degrees of advance. Instantaneous gas mileage was very high over 30mpg.

If one was to use too low an octane of gasoline and drive under these conditions the concern is the engine controller could not retard the timing enough to avoid detonation. Or the timing would be so retarded the engine would not run right. With retarded timing exhaust gas temperature goes way up. This subjects all components exposed to the exhaust gas to higher than "normal" operating temperatures. Exhaust valves, fuel injector tips, piston crown, O2 sensors are at risk of damage from running too low an octane grade of gasoline.

Running premium in a vehicle that calls for regular will have no benefit, in fact can cause the vehicle to run worse. Higher octane gas resists ignition more than lower octane gas and therefore can have an effect similar to retarded ignition timing.
That is not correct. That is higher octane gasoline does not resist ignition, it is just formulated to not break down into pre ignitable compounds ahead of the advancing flame front and from the rising pressure and increasing temperature arisign from the increase in pressure and and radiant heating.

However, once the flame front reaches the unburned molecules of gasoline they ignite with the same speed as any other blend of gasoline and the flame front advances through the chamber burning the mixture with all the speed of any other blend of gasoline.

There are a number of examples of engines that operate at engine speeds far above what our Dodge engines operate at and in some cases run much higher grade of octane. 93/94 (my Boxster engine was spec'd to use 93 and its red line was 7200 RPMs) and even 100 or higher. These engines do not suffer any from some imaginary slow to to burn higher octane fuel. Just the opposite. They are able to use much more ignition advance while avoiding detonation.
 

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More like bullet dodged. (No pun...)

Chances are the octane booster you bought and used only raised the octane rating by a few *tenths" of one point. IOWs, you raised the octane from 87 to 87.2.

Octane boosters that bring the octane up by whole numbers are expensive and not street legal.
I had 1/4 tank when I fueled up. I used this stuff. It claims 2 1/2 points at 20 gallons.

IMG_20200711_190346.jpg
 

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That is not correct. That is higher octane gasoline does not resist ignition, it is just formulated to not break down into pre ignitable compounds ahead of the advancing flame front and from the rising pressure and increasing temperature arisign from the increase in pressure and and radiant heating.

However, once the flame front reaches the unburned molecules of gasoline they ignite with the same speed as any other blend of gasoline and the flame front advances through the chamber burning the mixture with all the speed of any other blend of gasoline.

There are a number of examples of engines that operate at engine speeds far above what our Dodge engines operate at and in some cases run much higher grade of octane. 93/94 (my Boxster engine was spec'd to use 93 and its red line was 7200 RPMs) and even 100 or higher. These engines do not suffer any from some imaginary slow to to burn higher octane fuel. Just the opposite. They are able to use much more ignition advance while avoiding detonation.
Well, it depends on the car as to the advance curve.
 

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Well, it depends on the car as to the advance curve.
Automakers seek to run engines at the point of incipient detonation. This is where the best conversion of chemical energy to mechanical energy occurs. The advance curve is thus defined by the engine's behavior.

IOWs, the advance curve is not some hardwired curve but one that is very flexible and depends upon the engine and the signals from the knock sensors.

The advance has no bearing on the intentional behavior of high octane gasoline as the flame front approaches the molecules of gasoline. The octane contributing component of gasoline which happens to be named "octane" (or sometimes iso-octane) has more complex molecules of carbon/hydrogen which require more energy input to break these chain connections and thus allow the gasoline to form ignitable compounds.
 

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Well, I will defer to your knowledge. I am just recalling what I have run across in various articles.
 
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