Why does 370z require premium gas?
 

I'm just curious why it is that the 370z requires premium gasoline? I had an '85 300z back in the day and it didn't require premium fuel. I have a Mustang GT right now and it doesn't require premium fuel. Did the 350z require premium? Is it just an aspect of the VQ series of engines?

I'd imagine it has to do with the higher compression. If you use the cheap stuff you could damage your engine or at the very least lose performance and efficiency.

yah, high compression

I agree. :tiphat:

Higher compression requires higher octane. Higher octane gas has a higher ignition point. If you use lower octane gas, it will ignite too soon, thereby causing pinging (pre-ignition).

The mustang GT has high compression as well. However, you will note that it produces a lot less power on anything less than premium. Ford was smart and created a few different tunes in the factory computer. It will retard a bunch of things and happily (but less efficiently) run on lower octane fuel.

Nissan did not (and I don't blame them, if you buy a sports car, you should run premium if it requires it.) do this. It is a high-compression engine and you need to run the recommended octane at minimum.

yeah and i have a 1990 300zx and it also requires premium gas.

most of the japanese and european sport/performance cars require premium. My SR20DET swapped 240 did, my RX8 did, the 350 does, the S2k does.

I like that signature, Thorium! I'm in the same boat.

Thanks for the education, Z-owners!

at least premium isn't expensive as it was a couple of years ago when it took like $80 to fill up... :ugh2:

It's a whopping $0.20-0.30 a gallon more, for around 10whp or so (according to Ford, the mustang GT gets 412bhp on 91* and on 87* it gets 10bhp less, and 13#tq less). If you get 20mpg and drive 15K miles a year, that is about $200 a year for 10hp/13tq mod. A VERY! cost-effective mod in my book! You would have to put 25K miles or so on the vehicle to equal a cat-back in price, and this involves NO work and NO chance of voiding a warranty.

According to Ford, the mustang goes from 412 hp to 405 hp when changing from 91 to 87 octane.

402.

Besides, the way people talk about mods/hp gains for Z's on this site, 10hp/13tq is a LOT!

Further, the 91* tune that Ford uses is VERY conservative. People are getting a lot from just a tune on that car. I doubt Nissan is being nearly that conservative on their 332bhp V6.

i get 93 octance here in NJ, maybe thats why my Z pulled hard lol

As long as you aren't getting KR, then the lower the octane the better.

Maybe, maybe not. We do not really know... You really do not need to try and bash Nissan on everything. We can do that about ANY car company, Ford included. As long as there is human involvement, there will be somthing shady somewhere; all humans are imperfect.

However, it does not matter what Ford is saying in terms of HP. The 5.0 is way underated anyway. It is really pushing out about 430 HP...

Always sneaking in a jab here or there. :rolleyes:

it is truly uncalled for.

ImportConvert = magazine spec racer. imagination at work. :icon17:

yet hes still not banned :rolleyes:

Well, he hasn't made any personal attacks so I guess he's operating within the rules. Sometimes I question his motives...

I'm pretty sure it has to do with the engine and the compression ratio...If you have a Z, why not put the best in it...(Premium Gas, Synthetic Oil, etc).

I had an Acura Integra GSR 2001 :wtf2:that required Premium Gas.

I know my GTR also requires premium gas lol and same with my 370Z...I just listen to the rules, sucks now though because of my GTR's tune, I have to put higher octance fuel.

It's all about detonation resistance... when you have a high-specific-output powerplant like the VHR with high compression and timing pretty near MBT from the factory, you need the extra detonation resistance of 91+ octane fuel. With a factory tune, you'd probably be OK running mid-grade but the ECU would pull timing due to a minimal amount of knock. 85 octane would be a serious no-no unless you never rev above 3000 rpm at half throttle.

:iagree:

Interestingly enough, you'd get better mileage on 85 octane up until the point that the ECU started pulling timing due to knock. ;)

No-need to attack anyone personally. Sometimes there needs to be a devil's advocate, though. However, personal attacks really are unwarrented.

I agree. People will buy a sports car/high-dollar car and then want to run in it what they run/ran in their beater.

You don't feed a supermodel hamburgers and hotdogs.

Same reason why we eat clean food.

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.