Is high test really necessary?

IDZRVIT

The octane level an engine can tolerate is based upon a number of criteria and not limited to just the type of piston design e.g. domed for higher CR, dished for lower CR. CR can be altered by other means such as bore, stroke, deck height, head gasket, combustion chamber volume. The more critical ratio in determining what octane can be used is DCR, Dynamic Compression Ratio, which is always lower than CR. I won't explain it here because it would be a long thread. Google for more info if you want a better understanding of how it relates to octane levels and cylinder pressures.

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"America.... still builds rockets!"
Vette: 355 cid, 400 rwhp
'13 CTS-V Coupe: 6.2L LSA, 556HP

The BlueMax

The motor in the 370 is somewhat small IMOP so I would give it the octane it deserves. I get away without putting 93 octane in my 2nd generation LT1 because its such a lower rpm engine with low end torque. The Zs powerband is much more linear with most of the Hp & torque coming at higher rpms.

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The Blue Max

andre12031948

I'm not cheap or anything & can afford 93 octane but I noticed in almost all cases that when you buy 1/2 tank of 93 octane & mix it with 1/2 tank of 87 octane you'll pay less than if you bought a tank of 89 octane, plus in the first case you end up with 90 octane & a cheaper price. Anyone that wants/needs to budget their gas money should do some quick math & maybe consider mixing octanes. This would work even better in a gas station that lowers their high test/premium price because lack of customers or whatever reason.

I noticed that cause I also have a 95 4 cyl. 240sx se & want to use something more than regular. So....

IDZRVIT

Are you insinuating the Z is hard on gas and hence a need to budget your gas? Sorry, but the Z is not a gas guzzler unless you keep your foot in it all the time. My vette gets about 12 mpg and when I get on it, 8 mpg. Not complaining whatsoever. You gotta pay if you wanna play.

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"America.... still builds rockets!"
Vette: 355 cid, 400 rwhp
'13 CTS-V Coupe: 6.2L LSA, 556HP

Jordo!

Here's the bottom line:

Transient modifiers, recommendations for other cars, and general (or even expert, as in the case of several contributors to this thread) knowledge aside: If you can't or aren't attempting to monitor/actively tune around knock for the specific engine unit in question, you are stuck hoping the "black box" of the ECU is compensating sufficiently if you are using an AKI below recommended levels.

The default would be to follow manufacturer recommendations, if nothing else, in order to preserve the owner's side of the obligations of the warranty.

Once the warranty's out (or if it was never an issue), you are on your own to do whatever you like, but hopefully logic, reason, (and ideally empirical data, if it can be obtained) would inform subsequent behaviors...

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Enjoy it. Destroy it.