Fuel Octane Choice

[STBEAST]

I know there are a few previous threads on this topic. I bought my ST brand new and run 91 octane. My thinking is most all performance vehicles require high octane for best performance and to minimize the chance of engine knock, which over time can cause damage. My owner's manual states that my vehicle is designed to run on 87, but.......

I have never tried 87 and never intend to. But if I drove the car conservatively it should be ok? Gas is getting very expensive here in California!

 

[johnmarkp]

I was running mid grade gas in my 2019 ST until prices spiked.  Now I run 87 octane.  I never get any knocking and the engine runs strong.  I think I can tell the difference in how the car runs on different octane gas, but I am not sure.  

I may never go back to mid grade even if prices go down.

[Samurai Edge]

Why are you concerned shifting down to 87 octane?  The cost of fuel?

 

I only use 93 octane ( easily available her in the NE ) for two reasons:

  - 1.   I have always found the engine runs better on the higher octane

  - 2.  Having turbochargers makes it even more important, to me.

 

 

[STBEAST]

When I bought the vehicle, I planned on using premium fuel. Mainly because it is turbocharged (two turbos!) and is considered a performance vehicle.

I have heard on more than one occasion that people notice a difference in performance when they use a lower octane fuel.

That is because the knock sensor detects excessive knock and adjusts the timing, fuel injection duration etc. to protect the engine from damage.

Most people might not even hear it or know it is happening.

That should be enough for anyone. Of course, at the time I had no idea I would be paying 6 bucks a gallon for gas!

Saving a few bucks likely not worth it in the long run. 

[Samurai Edge]

I notice the difference when I had normally-aspirated vehicles.  I also notice the difference in my outdoor power equipment.

 

To me, it's worth the extra expense over a lower octane fuel.

Luckily, we are not at $6 / gallon for 93 octane, yet.  But we are getting there  🥲

[dabangsta]

The 2.7 in the F-150 and Bronco show on the dyno a loss of 15-17hp from the factory 325 when running 87 octane. Ford rates the HP with premium fuel (and mpg with 87).

 

When premium was $.20 a gallon more I would run it in my premium recommended vehicles. A slight SOP feeling of better power/driving, and probably due to changes in driving dynamics, better mileage (but even at $.20 a gallon more expensive it rarely was a wash, and more expensive to run premium). Currently most places local to be premium (91 here) is $.80 to $.95 more than 87 (and for those that care, $1.25 more than Unleaded88).

 

Personally I don't miss the 10 hp I lose running 87 octane in my SEL.

[STBEAST]

But is it ok? You are noticing a loss of horsepower due to running low octane fuel.  I get it. But if the engine is telling you "Run low octane get low performance" why is it even an option. To save a few bucks? Maybe worth it on a standard edge. But on an ST maybe better to run the best.

Not much discussion on using 89 and meeting half way.   ???

[Samurai Edge]

10 hours ago, dabangsta said:

The 2.7 in the F-150 and Bronco show on the dyno a loss of 15-17hp from the factory 325 when running 87 octane. Ford rates the HP with premium fuel (and mpg with 87).

 

Personally I don't miss the 10 hp I lose running 87 octane in my SEL.

 

I don't know where you got that info on the differences in dyno numbers between 87 octane.  15 - 17 HP compared to what?

 

As far as my reasoning for staying with 93 octane:

  - Yes, there is a felt performance difference

  - More importantly, the motor just runs better overall - Smoother, more responsive, etc.