Rec90 vs 91 Octane fuel
08-31-2022 | 08:17 AM
#11
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From: SW Ohio
Think your looking too far into things.
91 E10 has 91 octane
90 Rec has 90 octane
Yes, alchol itself has higher octane, but when the producer makes 91 E10 they mix the batch with 90% whatever octane fuel that mixed with 10% of their straight ethanol fuel, ends up with 91 octane.
Now, energy from 1 gallon straight fuel vs 1 gallon ethanol is a totally different thing.
91 E10 has 91 octane
90 Rec has 90 octane
Yes, alchol itself has higher octane, but when the producer makes 91 E10 they mix the batch with 90% whatever octane fuel that mixed with 10% of their straight ethanol fuel, ends up with 91 octane.
Now, energy from 1 gallon straight fuel vs 1 gallon ethanol is a totally different thing.
Yup. That's why I started this off with a comment about splitting hairs....
This is the info I was looking for.
Now, how about that one point of octane difference? Is it really that critical, or should I add a bit of booster to it if I use the Rec90?
Thanks. Brad.
(937)545-8991
08-31-2022 | 08:22 AM
#12
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From: SW Ohio
If you are absolutely optimizing the fuel burn then you will run the E10 or E15 probably a little fatter on lambda....maybe. It can really depend on the individual fuel. I live on the engine dyno and can swap back and forth to different fuels easily between various pump gasolines...I hardly change anything but am also not stuck using primitive engine controls. The ECU I use does a lot of the ***** work itself so I'm a little spoiled. Someone with more experience in these engines and control units could offer you better advice.
Best advice from SB....regardless of ethanol, MTBE, or whatever chemicals were used, the Rec 90 is 90 octane and the 91 is 91 simple as that. You'll only know if you can truly run it if you try it and don't hurt anything. Does the engine have a knock sensor and can it make adjustments?
Best advice from SB....regardless of ethanol, MTBE, or whatever chemicals were used, the Rec 90 is 90 octane and the 91 is 91 simple as that. You'll only know if you can truly run it if you try it and don't hurt anything. Does the engine have a knock sensor and can it make adjustments?
Yes. The Merc 496HO uses the 555 ECM and has knock sensor, and I'd assume it makes adjustments as needed, whatever that might mean (anybody know?). I'd just prefer to not rely on the technology side of it so much if it's just a matter of giving it the fuel it wants to begin with.
I have run it, and run it hard, on Rec90, and it didn't grenade on me. But I also know that incremental damage can lurk until the least opportune moment, and I'd much rather not discover where that point is.
Thanks. Brad.
(937)545-8991
08-31-2022 | 10:14 AM
#13
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From: Merritt Island, FL
If you are absolutely optimizing the fuel burn then you will run the E10 or E15 probably a little fatter on lambda....maybe. It can really depend on the individual fuel. I live on the engine dyno and can swap back and forth to different fuels easily between various pump gasolines...I hardly change anything but am also not stuck using primitive engine controls. The ECU I use does a lot of the ***** work itself so I'm a little spoiled. Someone with more experience in these engines and control units could offer you better advice.
Best advice from SB....regardless of ethanol, MTBE, or whatever chemicals were used, the Rec 90 is 90 octane and the 91 is 91 simple as that. You'll only know if you can truly run it if you try it and don't hurt anything. Does the engine have a knock sensor and can it make adjustments?
Best advice from SB....regardless of ethanol, MTBE, or whatever chemicals were used, the Rec 90 is 90 octane and the 91 is 91 simple as that. You'll only know if you can truly run it if you try it and don't hurt anything. Does the engine have a knock sensor and can it make adjustments?
08-31-2022 | 12:26 PM
#14
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Drag,
Yes. The Merc 496HO uses the 555 ECM and has knock sensor, and I'd assume it makes adjustments as needed, whatever that might mean (anybody know?). I'd just prefer to not rely on the technology side of it so much if it's just a matter of giving it the fuel it wants to begin with.
I have run it, and run it hard, on Rec90, and it didn't grenade on me. But I also know that incremental damage can lurk until the least opportune moment, and I'd much rather not discover where that point is.
Thanks. Brad.
(937)545-8991
Yes. The Merc 496HO uses the 555 ECM and has knock sensor, and I'd assume it makes adjustments as needed, whatever that might mean (anybody know?). I'd just prefer to not rely on the technology side of it so much if it's just a matter of giving it the fuel it wants to begin with.
I have run it, and run it hard, on Rec90, and it didn't grenade on me. But I also know that incremental damage can lurk until the least opportune moment, and I'd much rather not discover where that point is.
Thanks. Brad.
(937)545-8991
08-31-2022 | 01:22 PM
#15
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From: SW Ohio
08-31-2022 | 05:10 PM
#17
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From: Wyoming
Think your looking too far into things.
91 E10 has 91 octane
90 Rec has 90 octane
Yes, alchol itself has higher octane, but when the producer makes 91 E10 they mix the batch with 90% whatever octane fuel that mixed with 10% of their straight ethanol fuel, ends up with 91 octane.
Now, energy from 1 gallon straight fuel vs 1 gallon ethanol is a totally different thing.
91 E10 has 91 octane
90 Rec has 90 octane
Yes, alchol itself has higher octane, but when the producer makes 91 E10 they mix the batch with 90% whatever octane fuel that mixed with 10% of their straight ethanol fuel, ends up with 91 octane.
Now, energy from 1 gallon straight fuel vs 1 gallon ethanol is a totally different thing.
alcohol burns cooler and better than gas. If you’re at sea level stick to the octane rating. If you’re higher in elevation you can get away with a lower rating.
you can also buy octane boost off the shelf at any auto parts store.
i typically just buy airplane fuel. Stores for years and octane rating is like 110 . Has no alcohol in it
09-01-2022 | 10:44 PM
#19
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From: Traverse City MI
Octane is a scientific rating or measurement so yes the actual rating is important. Theres a common misconception that lower octane non ethanol rec fuel is better than higher octane fuel. It's simply not. The only thing non ethanol fuel may be better at is long term storage. But if you are using it frequently and adding fresh fuel frequently there's zero proof that ethonal fuel does any harm. Plus you can always add fuel stabilizer which I would add to any fuel during long term storage! Personally I don't and never have ran Rec fuel in anything and never will. Waste of time and money.
When they require 91 MINIMUM just run 93 premium and enjoy your engine upgrades. Not worth the little bit of savings to potentially hurt your engine.
When they require 91 MINIMUM just run 93 premium and enjoy your engine upgrades. Not worth the little bit of savings to potentially hurt your engine.
09-02-2022 | 12:59 AM
#20
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From: Gothenburg, Sweden
Like offshore excursion said
If your engine calls for 91 octane, you need to run 91, or you risk burning a piston or sticking a valve.
91 octane without ethanol would be better than 91 octane with ethanol.
However, 90 is less than 91, ethanol or not.
Now, the refiner typically adds a little bit of margin, so your 90 might test at 90.4. The engine manufacturer also adds a little bit of margin, so an engine that requires 91 might be fine at 90.2. But that is not a risk that you should take.
So 90 is a no-go, ethanol or not.
91 octane without ethanol would be better than 91 octane with ethanol.
However, 90 is less than 91, ethanol or not.
Now, the refiner typically adds a little bit of margin, so your 90 might test at 90.4. The engine manufacturer also adds a little bit of margin, so an engine that requires 91 might be fine at 90.2. But that is not a risk that you should take.
So 90 is a no-go, ethanol or not.
