Piston Slap: Focusing on Turbo 93 Octane Tunes?

Sajeev Mehta
by Sajeev Mehta

Mark writes:

Sajeev,

Thanks for the recent advice on winter tires & wheels for my new Focus ST. I took delivery of the car two weeks ago and I’m having a blast. The first thing I did when I got it home was take Bark M’s advice and sign up for the Octane Academy.

So here’s another question: What’s your take on fuel octane and the ST?

I’ve been running 87 octane per the owner’s manual and will probably continue for another tank or two, recording fuel consumption each time. Then I’ll switch over to 93 for a few tanks to see how mileage and performance stacks up. Everything I’ve seen says 93 will only give a 5 hp bump, so I rather doubt premium will be worth the extra cost in the short term.

But what about the long run? Do you think this turbo engine will be happier/cleaner/longer lived by running the expensive stuff?

By the way, I may order a set of tunes from Torrie, just like I did for my Mustang a couple years ago. I don’t know if that will make a difference in the questions above, but I wanted to make sure I mentioned it.

Thanks again!

Sajeev answers:

I’m kinda shocked that going from 87 to 93 octane only nets 9 hp with no change to peak torque according to Car and Driver. Anything is possible with modern computers and their numerous fuel and spark tables. So I recommend the 87 octane and oddball 17-inch Ford winter wheels for maximum hipster ironic-ness. The forum junkies will hate you for it!

Will this hurt you in the long run? I doubt it. Today’s computers are smart enough to keep that from happening. The dyno video above shows how the computer kills timing on the 87 octane tune — a fantastic reason to save money. It also shows how the FoMoCo factory tune is Dick Cheney conservative; easy on the environment, durability and fuel economy.

So why would you run 93 octane — ever?

One reason: The aftermarket tune.

When you get Torrie’s electro-goodness sprinkled on the ST’s computer tables, you’ll want to run 93 and never look back. I bet the aftermarket makes a great 87 octane tune that’s still safe but spicier than stock. However, if such a tune on my 2011 Ranger can net gobs more torque below 3,000 rpm (four-banger, mind you), it’s likely to happen on an ST. It all depends on the quality of the tune and the tuner behind the computer.

What say you, Best and Brightest?

Send your queries to sajeev@thetruthaboutcars.com. Spare no details and ask for a speedy resolution if you’re in a hurry…but be realistic, and use your make/model specific forums instead of TTAC for more timely advice.


Sajeev Mehta
Sajeev Mehta

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  • ERiic ERiic on Oct 01, 2015

    The 2.0L ecoboost in the Focus ST is rated for 252 hp on 93 octane. You'll have less power with 87 octane. The 1.6L ecoboost in the Fiesta ST 197 hp rating is also based on 93 octane. The reduction in power for the Focus ST and Fiesta ST using regular vs. premium isn't listed however if you look at the ratings for the Fusion with the 2.0L ecoboost it says: 240hp using premium and 231hp on regular.

  • Dougjp Dougjp on Oct 04, 2015

    93 octane isn't available close to where I live. So I'm only interested in reading about 91 octane tunes, and this is nearly impossible to find (with specific details/charts etc). I can understand why not, as most people even considering a tune want to go all out.

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