Too much octane or just a waste on a Roush boosted tune?

[94gt]

My 21' has the Roush tune on it for the Phase 2, which from what I have read is tuned for 91 min/93 recommended; Found a local station that has 116 octane, and one that has 110 VP Race fuel, I know that Roush recommends not adding "octane boosters" as it may cause issues (not sure if it is fouling or what when mixed with the gas?), but would running true 116/110 octane give me any benefit or it is just a waste of money on a car with a 91/93 tune?
I have always ran Sunoco 93/(94 when available) in my Mustangs, and they have always done well with it, but looking for that little extra when I take it to the track, but I really don't know if it would be worth it, or if would be bad?

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[NASteve]

Running leaded fuel shortens the life of the O2 sensors, but running a higher octane fuel will act as a safety net and keep you from detonating. But if you are not detonating now then there is very little to be gained putting higher octane in the tank, unless it is a oxygenated fuel like Q16, or you retune the car and ramp in the timing a little sooner. But once max timing is reach (whatever that maybe in a given application) then you gain very little if anything.

 

[94gt]

Running leaded fuel shortens the life of the O2 sensors, but running a higher octane fuel will act as a safety net and keep you from detonating. But if you are not detonating now then there is very little to be gained putting higher octane in the tank, unless it is a oxygenated fuel like Q16, or you retune the car and ramp in the timing a little sooner. But once max timing is reach (whatever that maybe in a given application) then you gain very little if anything.

Thanks, my buddy was just telling me saw it listed at a station, I didn't even realize it was leaded until you said it was. Sounds like it's definitely not worth the $18+ or so per gallon the way my car is set up.

 

[NASteve]

Run E85 if you can support it, ie fuel system.

The easiest way to look at it is if the tune is commanding XX timing and it is already seeing that timing on your current fuel, aside from the oxygenated stuff, going to a leaded race gas will not add power because you are already seeing max commanded timing on your current tune. But they can ramp it in sooner and avoid detonation which is what higher octane does.

If you go to a oxygenated fuel then like E85 you have to have the fuel system to support it because you will burn more of it.

 

[EFI]

but would running true 116/110 octane give me any benefit or it is just a waste of money on a car with a 91/93 tune?

There is rarely ever too much octane for a high compression boosted engine. A 110+ octane tune would have massive gains on your setup over a pump gas tune.

However, I see you mention running 110 on your current pump gas tune, which will mainly be a waste. Sure the ECU can adjust timing a bit running the higher octane, but it won't be noticeable without an actual tune for the new fuel.

This is all of course running E10 unleaded. Leaded gas is a whole nother story.

 

[94gt]

There is rarely ever too much octane for a high compression boosted engine. A 110+ octane tune would have massive gains on your setup over a pump gas tune.

However, I see you mention running 110 on your current pump gas tune, which will mainly be a waste. Sure the ECU can adjust timing a bit running the higher octane, but it won't be noticeable without an actual tune for the new fuel.

This is all of course running E10 unleaded. Leaded gas is a whole nother story.

At this point I am still under warranty and plan to move to E85 when the warranty expires (8/2024) and changing the tune on my car would also void the warranty to even go up to 110/116 (Roush tune)
Thanks to both of you for the explanation. , I was looking at it from the perspective of on stock tune, it will adjust for 87 - 93, and was thinking that with the 93 tune that was a "minimum" not a set point for the timing, where it would allow itself to adjust for the high octane, and while it does sound like it will adjust a bit, just not enough to make it worth the price of the fuel.

 

[Grimreaper]

Mix in enough for 97 or 98 octane and see how it runs.

A few degrees on timing can make the difference between a moderate thrill or "this was worth $8k" feeling.

Sure the sensors can adjust but they are reactive and require it to knock first. Roush does keep the adaptive knock active but its reactive too.

 

[tosha]

Didn't know octane booster could cause issues. Could you please share more details?

 

[94gt]

Didn't know octane booster could cause issues. Could you please share more details?

I'm not sure it's just listed in the Roush warranty.

 

[tosha]

Interesting, thanks. seems more like a safety net, but thanks for sharing. Not sure how they would even determine the use of regular octane booster. All the good octane fuel (e.g. 93-94) already comes with these additives from a pump.

 

[wazslow]

Interesting, thanks. seems more like a safety net, but thanks for sharing. Not sure how they would even determine the use of regular octane booster. All the good octane fuel (e.g. 93-94) already comes with these additives from a pump.

A lot of octane boosters use MMT which will turn your spark plugs orange. Pump gas does not have MMT.

 

[tosha]

A lot of octane boosters use MMT which will turn your spark plugs orange. Pump gas does not have MMT.

Ok, that makes sense, some boosters in fact are advertised as "barely streel legal"

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