Guess I'm showing my age

I've been around "older" car people quite often and I've never heard this term.

All I can get here is 87/89/91. No 93. But there is 103 available for like $11/gal.

You say "yes and no" but as far as I can tell you are agreeing with me. Plenty of cars run 11:1 fine on 87/85 octane gas, the Z simply wasn't designed for it.

sell your Z now, op

91 is fine.

I'm saying that yes, it is possible to run a high CR piston on octanes < 91, provided the spark advance tables are properly tuned for it, but no, the Z was -- at least according to Nissan -- not tuned for it.

Also, there are indeed special considerations for octane needs unique to the design of higher compression pistons, and it is unknown (or at least not widely known) how the VQ37HR pistons behave in terms of hot spots under load.

So, I'm agreeing with you, but calling attention to the potential unique needs of higher CR pistons, in much the way that Sh0velman was pointing to potential exceptions associated with running motors at higher altitudes.

I don't know how much of a role the piston crown design and specific CR is playing a role in octane needs for the Z's motor relative to the tune alone, but it is indeed possible.

I do know this tho': In the owner's manual it says some light knock when chugging up hill is "normal"... :icon14:

http://www.the370z.com/members/jordo...ock-normal.jpg

That alone tells me this motor prefers higher octane fuel.

91 is fine.

That's all that's available here too.

Maxima says that or something similar too

Always helpful to have an echo.

Yeah... I see your point.

You know, the only thing more annoying than an "echo" post is someone who insists on having the last word in a thread.

the knocking, which is not optimum, but is compensated for in modern aluminum, computer controlled, etc engines comes at a rare peak time when all the variables are pushed in the maxed aspect. tracked, 110 degree ambient air, buzzing the motor, lugging the motor, sea level elevation etc. Modern aluminum head design, machining and casting is light years advanced from old sand cast steel heads and hot spots are quite rare. despite all the "if you can't afford it" comments and "if you want it to run like it shoud/get max hp" suggestions, running less than 91 won't kill you or your engine if you are not flirting with all those variables being maxed out.

for many of us that includes winter driving, grocery getting long flat highway trips. the sky won't fall. That said, do what you want and chose to disagree if you like:)

FWIW, I've got two race jeeps, one dyno tuned to run on 93 pump gas and the other gets a 96 blend due to more timing and boost. When we dyno tuned the L92 (LS3 derivative) it was stoooooopid how much timing we put in it to make more power. The OEM's set them up way tame for warranty considerations.

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.

My 2 Cents
 

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.

I use 93 octane
 

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....

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.:tup:

Honestly chief, as a number of people on here have said, if the cost of fuel is causing enough issues in your budget that you are mixing octane levels just to save a few bucks, you may want to consider parking the Z in the garage and using it as a toy / weekend car, and getting yourself a daily driver that is fine with 87. Virtually all high-end sports cars say that they need the premium gas, it comes with the territory.

That being said, it all depends on what you are aiming for with the Z. If it is your daily driver (which it is in my case, but I live 4 miles away from work), you really should have budgeted for the increased fuel cost when you got the car. Shaving a few dollars off the fuel bill, while seeming to make good fiscal sense, flies right in the face of the fact that the Z is not a very fuel economical car to begin with.

And if the purpose of having your Z is just to have a fast car that you can play with, but don't necessarily drive all the time, then why would you want to hurt it's performance just to save a few bucks?

Sometimes a very minor octane difference can make a big difference. In our area some stations sell 92 octane as premium while some sell 93 octane. One of my previous Z's was a 300 ZX TT running 14psi boost. It could tell the difference between the two and expressed its unhappiness!:tup:

93 should be fine, but then again nobody cares about premium gas when u are flooring it 24/7. :)

Actually, that kind of use would be exactly when you would be concerned about making sure you have the highest octane fuel possible.

yeah :confused::confused: with that statement

I use to run 87 in my juke ( says to use premium for performance)

any how i would get about 25 miles to the gallon.

i then tried 93 and im up to 29.7

when i break it down to the penny. it cost 16 cents per mile on 87 and 14 cents per mile on 93

Run the super unleaded

My octane level that I use is H2O and she's a beast in reverse, and I get 36mpg.

My Frontier also, but I find running premium I get better mileage, so for the extra couple bucks that's what goes in.

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...

Well said, Jordo.