If the argument is thatHonda engines were designed for 87 octane:

Why does Honda and Toyota state that unleaded gasoline of "86 or higher"?
Why does Haynes Honda manual state "Knock sensor - The knock sensor is a piezoelectric crystal that oscillates in proportion to engine vibration."?
The only recent engine I know of that does not have a knock sensor was the 01/02 Mustang Bullitt engine.
Meaning that under certain conditions, the driver could damage or destroy the engine with a heavy foot.
Rather incredible since my 87 Sable 3.0 has a knock sensor that Ican detectunder load.

High compression engines will only operate well on Premium octane.
Alimitation due to compression ratio.

Would Velocifero please state the BTU of Regular, Mid Grade, Premium rather than "often contain more energy per litre"?
The ICE (pig) is driven by BTU.

I got the E85 backwards: It's 85 percent beverage grade alcohol and 15 percent gasoline.
Indy 500 today ran on E98 ratherthan past 40 years Methanol.
Methanol = denatured alcohol.

My test:
Mid grade cost is 4 percent over Regular.
To be cost effective I must have 1.2 MPG Mid grade over Regular freeway driving.
Less than 1.0 around town.
Otherwise the choice is Regular.

 

I am, by no means an expert on this, but wasn't the pre 87 octane better than the 87 we have today? Reason I ask is b/c the 87 today has up to 10% in volume of Ethanol. Ethanol has less BTU's than gas, so, wouldn't our engines benefit going up to 89 octane to compensate for the slight loss in BTU's?

Some people noticed a MPG drop when they started introducing Ethanol into gas.

E85 and Bio-Diesel are the same, but different.[&:] E85 is somewhere in the ballpark of 105 octane (but less BTU's than 93), and Bio-diesel is about 50 cetane or higher (compared to 40-45 cetane of regular #2) and also has less BTU's. E85 is the way to go but you'll have to get a custom tune to benefit from the increase inoctane. Its hard to have your cake and eat it too.

I might just step up to 89 the next go round and see what, if anything, happens.

Beau

 

a lot of places do have 10% ethanol in volume for all 3 grades of gas. luckily, i still have the option of buying the regular good old 87. here the ethanol is in the 89 octane gas.

 

Nissan 3.5 is premium due to compression ratio of 10.3:1.Honda J30A4 10:1 is high considering the minimumrecommended 86 octane.
The PCM contains one or more timing maps. These Honda designed maps are Y axis RPM and X axis load. Load is calculated from the intake air sensor on the V6. Basically the sensor calculates temp drop of a heated wire from airflow and converts to engine load. The intersection X and Y is the timing advance number.If the load value advance results in incipient knock, the knock sensor stops the advance
I haven't been able to verify if the J30A4 has a high octane map but my guess is that it does given 10:1.
If this is true, the engine should recognize higher octane gasoline because the PCM "learns" in closed loop.
Don't know if this is done in 20 miles or one tank.
Whether Mid Grade would make a difference depends on load map design at, say, 70 mph cruise freeway.
I have no interest in stop light performance.

Conventional advice is to use lowest octane that the engine will run on without knocking. Regular unleaded for J30.

To crank out the advertised 240 hp, Honda test obviously used premium gasoline to achieve the desired advance.