[Blue2]

Our local track has 93, Sunoco GT 100 octane (unleaded), and higher octane race fuels all at pumps. Any benefit or harm in adding a gallon or two of 100 octane to a tank full of 93 octane before hitting the track? Car is stock, no tune.

[BigKutta]

I think there is 0 benefit going higher than the recommended octane. I dont think it buys you speed, performance,etc. Maybe if your engine is knocking, which it shouldn't with 91/93 octane

[DanG]

There is no benefit unless you have a tune that requires a higher octane.

[infinitekidM2C]

No harm i can think of other than wasting $$ lol. I'd stick with adding a bit of 93.

[Thescout13]

Originally Posted by BigKutta

I think there is 0 benefit going higher than the recommended octane. I dont think it buys you speed, performance,etc. Maybe if your engine is knocking, which it shouldn't with 91/93 octane

Not sure if this is true with modern BMWs though because of the VANOS and the DMEs ability to change timing. I seem to recall a Steve Dinan video on YouTube where he breaks this down and how it works on modern turbo BMWs (without a tune) vs older NA cars. We aren't talking about 50hp here (that requires a tune), but some benefit. Though 100% agree that need a tune to fully realize any substantial benefit.

Though I could be remembering wrong. If you are in a 91 state, mixing in some higher octane definitely helps get up to 93+. There is an appreciable difference on a dyno with a car on 91 vs a car on 93.

[MrOhnoez]

You will only benefit if your car is pulling timing already. It'd be so minimal anyways I don't think it's worth the money.
As others have said, if you tune the car to run on 100 octane then oh boy it'll have some fun.

[Commanderwiggin]

If you're going to be on the road course, autocross or high speed sprints an extra bump in octane will provide you with more power and will be safer. It won't be a ton more power but it will definitely be more than your oe calibration would allow on 93.

[pizza240]

I'm pretty sure that you will get slightly more HP but same torque.

This was the case on my 2.0L turbo Focus ST and was proven with some dyno info nearly 7 years ago.
Granted, that car could take 87 Octane, and (of course) it's not a BMW.
But I remember it was 240hp with 87 and 252hp with either 91 or 93 or 94, I forget which of the latter... it might have been 255 or something with 94 oct.

Torque was always the same regardless of octane.

Never had any issues with any car going from one octane to another, even if I went from 87 to 94 in the Focus. Felt faster and more wheelspin with 94. Burned more efficiently with higher octane as well, but not enough to make the higher octane worth the extra $$$ for long trips.

I'd try to empty the tank of 93 as much as possible before refilling with 100... but it probably won't do any harm if you mix.

[VisualEcho]

Correction.

Stock tune is made for 93 octane, although not all locations in the USA have 93 octane available, so the hp/torque figures you were sold in the brochure are a lie.

Brilliant.

[Commanderwiggin]

Originally Posted by VisualEcho

Stock tune is for max 91. Even 93 will not give you any more power unless you're tuned for it.

If you have an OTS 93 octane tune, then it won't help you there either.

The ONLY way you're going to get benefit from 100 octane is to have the car tuned for 100 octane.

This is fake news. The stock calibration recommends 93octane to begin with. The knock sensors will detect more knock on the 91 octane and the ecu will pull timing and this will reduce the power especially when everything starts to heat up. With higher octane fuel including additives such as boostane, this will reduce the timing corrections.

[ssabripo]

Originally Posted by VisualEcho

Stock tune is for max 91. Even 93 will not give you any more power unless you're tuned for it.

If you have an OTS 93 octane tune, then it won't help you there either.

The ONLY way you're going to get benefit from 100 octane is to have the car tuned for 100 octane.

this is incorrect. The Stock tune from factory is set for 93 octane.

[TheRealOrosie]

Originally Posted by VisualEcho

Stock tune is for max 91. Even 93 will not give you any more power unless you're tuned for it.

If you have an OTS 93 octane tune, then it won't help you there either.

The ONLY way you're going to get benefit from 100 octane is to have the car tuned for 100 octane.

Gotta love the Internet.

[VisualEcho]

I stand corrected.

Now I'm going to suggest that a stock tune on a USA car that requires 93 octane to not pull timing is, well, fucking stupid.

Leave it to the Germans.

[TheRealOrosie]

Originally Posted by VisualEcho

I stand corrected.

Now I'm going to suggest that a stock tune on a USA car that requires 93 octane to not pull timing is, well, fucking stupid.

Leave it to the Germans.

93 here no problem. Just lucky I guess. One of the things I really don't miss about Cali.

[MystroX5]

Originally Posted by TheRealOrosie

93 here no problem. Just lucky I guess. One of the things I really don't miss about Cali.

Me too. I run Sunoco 93. They just put a new Sunoco station 3 miles from my rural home. I run it in all my toys.

[243Racing]

I thought I read something on here that 100+ octane race fuel would damage the car in some way?

Any issue adding 100 to 91 to make (effectively) 93?

The nearest 93 to my local track is 63 miles away, which is like half a tank in the M2

[Commanderwiggin]

Originally Posted by BeastieBombRacing

I thought I read something on here that 100+ octane race fuel would damage the car in some way?

Any issue adding 100 to 91 to make (effectively) 93?

The nearest 93 to my local track is 63 miles away, which is like half a tank in the M2

Negative, 100+ octane "Unleaded" race fuel will not damage anything. It will provide better knock resistance and allow the car to run at the full potential of the factory calibration with less timing corrections. 100+ octane "leaded" will foul your cats if you have those still; that might be what you were told as far as damaging.

You can bump a little 100oct or add boostane to improve the octane if you'd like.

At one of our local tracks they had 100oct at the pump and I filled half my tank with it to give my car some extra knock protection while I was having some fun in the heat. A little unleaded octane increase is definitely not a bad thing.

Now with all the above, if you're regularly spending $$ on 100oct I would suggest perhaps going to a flex fuel tune via Ecutek if E85 pumps are readily available...E85 fuel costs are significantly cheaper and with a flex fuel sensor installed in the fuel line your ecu will always run the optimal timing without the need to reflash. You also have the ability to quickly switch maps via the steering wheel for different modes such as Valet, Street, Road Course, Drag as examples.

[D CHOI]

I add 100 octane to the bad 91 in the west coast all the time. Even in stock form u can feel the difference with the engine being happier and higher rpms Rev more effortlessly.

I have the BM3 tune so when I'm on the 91 map or 93 map I would add 3ish gallons to the tank since it will be required. But in the ACN 91 map tune with 100 octane I can feel the difference too. I've tried running the full 100 map once and that was fairly impressive. Power jump obviously much higher from 93 to 100 than 91 to 93. The burbles are more potent as well.

The only downside I know with mixing 100 octane vs getting a pure 93 octane is u would need to replace ur spark plugs sooner. Also it can damage the cat as well but I hope it's just the leaded ones that will since I use unleaded. I recently replaced the stock plugs that lasted 11k miles from BMW that replaced for me at 25k miles. I end up getting the NGK 1 step colder plugs and car is running like a champ now.

[243Racing]

Originally Posted by Commanderwiggin

Negative, 100+ octane "Unleaded" race fuel will not damage anything. It will provide better knock resistance and allow the car to run at the full potential of the factory calibration with less timing corrections. 100+ octane "leaded" will foul your cats if you have those still; that might be what you were told as far as damaging.

You can bump a little 100oct or add boostane to improve the octane if you'd like.

At one of our local tracks they had 100oct at the pump and I filled half my tank with it to give my car some extra knock protection while I was having some fun in the heat. A little unleaded octane increase is definitely not a bad thing.

Now with all the above, if you're regularly spending $$ on 100oct I would suggest perhaps going to a flex fuel tune via Ecutek if E85 pumps are readily available...E85 fuel costs are significantly cheaper and with a flex fuel sensor installed in the fuel line your ecu will always run the optimal timing without the need to reflash. You also have the ability to quickly switch maps via the steering wheel for different modes such as Valet, Street, Road Course, Drag as examples.

That’s what it was - leaded. Thanks.

After this event I’m going to a) get tuned for 93 and b) start bringing cans of it to the track with me.

[Mdkcrf250r]

To sum it up, the car will only benefit from higher octane if the stock calibration is already pulling timing (due to poor quality fuel, etc) so the higher octane fuel will only get you back to where you’re supposed to be anyway. I’d say definitely go for it.

[Mdkcrf250r]

It’s funny how everyone questions the content of e85 but nobody questions the content of 91/93.

[omasou]

Sunoco in my area offers 91 and 93. I can definitely tell a difference—car runs better/smoother—when running 93. Even the X5 ran better.

As one poster mentioned, make sure the race gas doesn't contain lead or you'll kill the cats.