soy hamburgers and hotdogs? shes gonna throw them up anyways

The short answer is: Because it may ping under load without it.

Basically the engine was designed (e.g., compression ratio) and tuned (e.g., ignition advance) to make optimal power on 91 AKI / 96 RON.

That said, it is worth noting:

1. The owner's manual claims it may ping under load anyway :ugh:

2. It runs very rich approaching fuel cut; rich mixtures cool the combustion chamber with unburnt fuel, and acts as an anti-detonant.

I have been feeding the Z 93 octane, but the wife's Maxima owner's manual says use premium and we have fed it a steady diet of only 87 regular for 66k and I have never heard a ping, even heading up hill with a full load of passengers.

You've more reading to do young padawan :tiphat:

It's actually the slowing of the flame front that brings the reduced chance of detonation with a richer mixture. That extra atomized fuel doesn't really do much to decrease the detonation threshold by reducing combustion chamber temperature. It's basically like a drop in a bucket.

I appreciate the technical explanations, but I'm also curious about the design decision itself. To wit, as I said, my '85 300z did NOT require premium fuel. As well, my 2006 Mustang GT does NOT require premium fuel.

So obviously it's not absolutely necessary for a premium sports car to use premium fuel. So why did the Z's designers decide to go this route? Is it just for the extra cachet of having to put the "best" fuel in your sexy sports car? Or is it simply a case that in order to get the amount of horsepower out of an engine the size of of the Z's engine, they *have* to use premium fuel? (kind of like how Nissan recommends that you use ester oil)

My thinking here is that if you're going to create an "economy" sports car (relatively), it would seem like a wiser decision to design it so it can run on regular fuel, especially for a relatively low-mileage car like the Z. This will be even more of an issue as the US economy recovers and gas prices, once again, go up, up, up.

You probably won't hear it. It will either peel a piston like an onion, or your ECU will retard timing and increase injector pulse cycle or a complex combination of things.

It's because it allowed them to rate the engine at 332bhp instead of something like 312.

Every 1/2 point in compression you go up, is about 15whp. Running 91* instead of 87* will allow for roughly .75-1 point increase in compression or so, given similar tune, and considering the use of aluminum heads.

So...would you like the extra 20-30hp, or do you want to cheap out and not have it?

I don't get why people whine about the price of fuel on a vehicle that serves no purpose but to have fun. If it were about "need", you would have an Altima or Maxima. It's not. It's about want. So pony up.

Another point is that manufacturers are caught up in the "numbers marketing" game. Witness the 5.0's threat. There are subjective reasons for buying a car, and objective ones too. Car manufacturers can get their hands around the objective numbers, and design to that.

You've got a V6 in a sports car, raise the compression = higher hp/tq numbers, possibly better sales.