okay everyone, i am about to show my ignorance as far as cars go. my question is why must we run the premium gas for our cars?? I am not saying that I wouldnt run it even if we did not have to, I mean, if i had the money to buy the car and cover the insurance, premium gas is not going to hurt me. I would do it even just to take care of her. i could do without these latest price hikes, but for the entertainment the car gives, i still consider it well worth the price of admissionn.

the main reason i ask is because my last car was a supercharged grand prix GTP and was told that I had to use the premium for that because of the supercharger. from my understanding, our Z's are straight up NA, no charger at all super or turbo. So thats it, easy question, why must we use the premium gas??

 

High compression ratio = higher octane.

 

thanks a lot, easy answer to an easy question, period...

 

its not just the compression ratio its also the cvtcvs sytstem which drastically ramps up the ignition timing in the upper rpms.

 

is there really a difference between 93 and 94 octane? every Sunoco around here has 94, but they charge like 10cents more per gallon

 

a good question. i dont have the answer but pose another similar question. when i had that grand prix with the supercharger, the manual noted that premium grade was 91 and above, and if in emergency I could run 89, but only gingerly and for not that long or else I would experience a knocking in the engine. I assume that this would be the same then for the Z. Not that I ever let the gas tank get that low, heck, hardly ever under half, but sometimes out in the country, those "podunk" gas stations only offer as high as the middle grade, or 89 octane. It would be nice to know if i could run that stuff even if to just get enough miles to get to the next station that had premium. what are your takes on that???

 

Not that easy. The main advantage of premium-grade gas is that it allows automakers to advertise a few more horsepower by designing and tuning engines to take advantage of premium's anti-knock properties. But auto engineers generally agree that if you use regular in a premium engine, the power loss is so slight, most drivers can't tell.

Today's engines use highly evolved versions of a device called a knock sensor to adjust settings automatically for low-octane gas. And more engine control computers have adequate memory to allow separate sets of instructions for various octanes. The engine control computers keep pushing to maximize performance on whatever grade of fuel is used.

The only modern engines that should really need premium are those with superchargers, which force-feed fuel into the cylinders. "You're driving along and just tramp the gas and the knock sensor cannot sense the knock fast enough in some cases," because the supercharger boosts pressure so fast, says Bob Furey, chemist and fuels specialist at General Motors.

Burning regular when the owner's manual specifies premium won't void the warranty, nor damage the engine, even the most finicky automakers say. "You're giving up perhaps just a little bit of performance that a customer wouldn't really even notice, it's so slight," says Furey.

All Porsche engines are designed for premium, too, but it's not available everywhere. "Our cars must be able to drive all over the world, and so we are able to run on regular," says Jakob Neusser, director of powertrain development at Porsche's research and development center in Weissach, Germany. "You don't have to feel that a mechanical problem or anything else will happen" using regular gas, even in the highest-performance, regular-production Porsches.

Premium, in fact, sometimes is worse fuel than regular. It resists knock because it's harder to ignite than lower-octane fuels. As a result, some engines won't start as quickly or run as smoothly on premium, notes Gibbs, the SAE fuel expert.

High-test does have a potential fuel economy benefit. It is slightly denser than lower-octane gas, meaning there's a little more energy in a gallon. But the small difference is hard to measure in real-world use, and that same density can contribute to undesirable buildup of waste products inside the engine.

http://www.usatoday.com/money/autos/...emiumgas_x.htm

 

hehe...what a contrast to the reply by flyzmd80 (length-wise)

 

i just learned something new today. good question.

 

The best I can find in SoCal is 91 octane. T.T

 

Not to be the argumentative one, but I thought the VQ35 was considered a low-compression engine? Am I mistaken?

 

i use 93 and 94 octane... mostly 94 from sunocco but after the price hike i save the 10 cents and just put 93 in.

 

my dad's friend who has a 69 stingray corvette, and a c5 vette said he has never used nething but regular for his sports cars, and using regular has never damaged his engine. as indicated in above posts, theres probably performance loss, that artical from above says its roughly 5%. It really shouldnt matter much as far as everyday driving goes... but... "everyday driving" is not what you got ur Z for is it?

 

From what I've read their is little difference in the two grades. And the difference is due to the car actually retarding the spark to prevent knock. Because the premium ignites at a higher temperature there is no need to retard the spark and their is no knock with the full spark. The lower grade gas knocks with the higher spark and temperatures from the sparkplugs.

 

The 350Z has a 10.3:1 compression ratio. This isn't super high, but it's up there. Some highly tuned naturally aspirated street cars (such as the Honda S2000 or the new Audi S4 engine) do 11:1 and higher. Off hand I don't know of any street cars that do 12:1 and still run on normal pump gas. At that point they are typically using very high octane race gas.

A lot of the larger displacement American engines now days use compression ratios down in the high 9.x:1 range.

Many forced induction engines often go from 9.5:1 and lower. My Audi's 1.8t turbo engine had a 9.5:1 (I believe the newer ones are 9.3:1), and a lot of the hardcore boost guys will modify their engines down to 8:1 to handle huge boost. In these cases, though, you still have to run high octane because of the boost.

 

In Australia we run 98 octane at most gas stations.
Not sure if the way they calculate it is different since out lowest grade is 91 though???????

 

in the United States, we calculate Octane by (Research Octane Number + Motor Octane Number) / 2 = advertised Octane #. At least that is what i remebered during my chemistry studies during college.

e.g. (RON+MON)/2 that is seen in US gas station.
In Asia, the advertised octane is either RON or MON.. i don't remember which one gives a "high #" given the same grade of gasoline.