Can I run 87 octane fuel on a 93 octane tune?

[Mchris2725]

My fiesta is stock besides the RMM. I purchased a COBB accessport and want to put map the 93 octane tune today. The only issue?? I currently have 87 octane gas in the tank! (about ? full). So?a few questions.

1. Is it ?safe? to run 87 octane fuel on a 93 octane tune?
2. Should I fill up the remainder of the tank with 93 octane and run the 93 octane tune?
3. Or, should I fill up the remainder of the tank with 93 octane and run the 91 octane tune?
4. Should I just wait patiently for an empty tank to remap?

I know I should probably be patient, but I am still curious what the consequences are if you run lower octane fuel on a higher octane tune.

Thanks all.

Matt

 

[boombots]

You should wait it out... You could go for a long drive!

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[Racer83L]

just drive inefficiently.... let the engine sing. a/c on, windows open.

I could empty it in a night for you if you lived closer.

 

[NJBooST]

Don't do it. Ignition corrections, knock, unhappy pistons, unhappy wallet.

 

[OffTheWall503]

I'd say run it out to roughly 1/8 tank if possible then fill with 93. Not worth risking potential damage on a tune that is meant for fuel that is 5 octane points higher.

 

[Mchris2725]

Update: Ran it down to about 1/3 a tank on the way home from work. Then I filled up w/ 93 octane. let the car idle for 15 mins to let the pure 87 run through the fuel lines. Installed 91 octane tune. Drove to the beach and noticed more power about 1/2 the way there with my butt dyno. No issues yet but so far so good! Planning to re-map to 93 tune after this tank. The car drives much differently now. Also, more vibration under idle with the new motor mount. Just hit 3,000 miles and can't wait for the next upgrade! Thanks for listening and for the recommendations.

Matt

 

[M-Sport fan]

Is that a Cobb RMM in it now?

 

[Mchris2725]

Yessir. Cobb mount. Only installed the mount last week so it might need some time to break in some more. But it's only vibrating under idle. I know it's not too bad because my dad drove with me and didn't say anything about a vibration at idle (and he's pretty critical/observant)

 

[Fiestarawpower]

Turn the AC on, you'll definitely feel the vibration.

 

[Tiralful]

Turn the AC on, you'll definitely feel the vibration.

True sorry lol. Although my E30 tune from Adam fixed it somehow, he's a damn wizard.

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