Car and driver just have an ariticle today regarding premium gas. It used BMW M3 as one of the performance vehicle. This may also apply to the G35s.

http://www.caranddriver.com/article....&page_number=1

"Is premium fuel worth the premium price? Can you hurt a high-octane car by running it on the cheaper stuff?"

"The results were more dramatic with the test cars that require premium fuel. The turbocharged Saab's sophisticated Trionic engine-control system dialed the power back 9.8 percent on regular gas, and performance dropped 10.1 percent at the track. Burning regular in our BMW M3 diminished track performance by 6.6 percent, but neither the BMW nor the Saab suffered any drivability problems while burning regular unleaded fuel. Unfortunately, the M3's sophisticated electronics made it impossible to test the car on the dyno (see caption at top).
Our tests confirm that for most cars there is no compelling reason to buy more expensive fuel than the factory recommends, as any performance gain realized will surely be far less than the percentage hike in price. Cheapskates burning regular in cars designed to run on premium fuel can expect to trim performance by about the same percent they save at the pump. If the car is sufficiently new and sophisticated, it may not suffer any ill effects, but all such skinflints should be ready to switch back to premium at the first sign of knock or other drivability woes. And finally, if a car calibrated for regular fuel begins to knock on anything less than premium or midgrade, owners should invest in a tuneup, emissions-control-system repair, or detergent additives to solve, rather than bandage, the root problem. Class dismissed."

 

Great find.

 

I agree, good find.

It's amazing to see people put in premium when their motor is designed to run on 86/87. You hear "My baby is worth the extra protection" and the like. Run what the manual tells you to run, and don't deviate from it unless you just can't find premium for some reason.

 

This is straight out of my 05 6MT Sedan maunal:

Sedan — Manual transmission and Coupe models

Use unleaded premium gasoline with an octane rating of at least 91 AKI (Anti-
Knock Index) number (Research octane number 96).

If premium gasoline is not available, unleaded regular gasoline with an octane
rating of 87 AKI number (Research octane number 91) may be temporarily used, but only under the following precautions:

-Have the fuel tank filled only partially with unleaded regular gasoline, and fill up with unleaded premium gasoline as soon as possible.
-Avoid full throttle driving and abrupt acceleration.

However, for maximum vehicle performance, the use of unleaded premium gasoline is recommended.

 

I have an '03 sedan 5AT, and my manual recommends at least 91 octane as well.

 

But it isn't to the same level. With the 05's, and the coupes before, lower than 91 octane could only be used for a limited time.

The older sedans could be run all the time with 87, but they just recommended 91. I've never noticed a difference, and any mileage differences seem trumped by other issues, like driving differences and head winds.

 

"91 AKI (Anti-Knock Index) number (Research octane number 96)."

What number is the one posted at the gas pump?

 

Here it's Research method + Motor method / 2 = posted Octane rating

Research method is found by chemical analisis
Motor method is found by actually running it in a small engine and finding the detonation point.

 

My '04 Sedan manual says to use at least 87 on one page, 91 on the next page. We ran 87 a couple tanks worth, then found BP in our town selling 91 octane for the price of 87 on weekends. We always fill up on Saturday. My wife drives the car, claims performance is better. The fuel economy is 1 to 2 mpg better.

 

My pleasure, although I won't take credit for the answers. They're in your Infiniti Owner's Manual. If you'd read it, and adhere to its recommendations (not requirements; that's a different matter entirely), you might not be so confused on the matter.

Nissan recommends premium fuel in all VQ35DEs AFAIK. It was recommended in my Altima; it's recommended in the Maxima; it's recommended in your G. It is not required but for a few, such as the '05 6MT models of the G35. Nissan engineers do not blindly set out to cost you money for no reason. They're telling you that if you want to reduce ignition retardation due to low octane, run at least 91 octane in your G. Retarding your ignition timing to prevent predetonation won't hurt a thing except performance, and then only slightly. The Car and Driver bit posted earlier lines up with this assertion quite well.

Run what you want, calejohnson, if you drive any G35 but an '05 6MT. You'll pay a few cents less at the pump and have a little less giddyup in your car. Hey, you can also run Wal-Mart's Tech2000 cheapie oil to save a few more pennies if you like. Stick a Wal-Mart rebranded oil filter on there too; that's worth at least a buck. And if you take offense to my calling people who employ these practices as owners of precision-engineered, high-output RWD sport sedans "cheap bastards," my apologies. You need to grow thicker skin.

Really, I just don't get people spending a rather large chunk of cash on this car and not following Nissan's black-and-white recommendations...

 

I fill up with premium (91) every third fill up and use midgrade (89) every first and second. I have never noticed a change in performance and I'm a pretty aggressive driver. I don't do this to be cheap. I do it because I've done my research and I know it can be done without any ill effects. So in the end, at least in California, I'll save $100 a year...And that goes directly towards car detailing products. hehee

 

My 2004 owners manuel states." SEDAN MODELS
Use unleaded regular gasoline with an octane rating of at least 87 AKI (anti knock index) number(research number 91)."

Our fuel stations pumps have AKI octane ratings on them. The car runs fine on 87 but slighly better with mid grade. However, the 04 coupe models need the 91 AKI octane(premium fuel)

 

05' MT6 sedans say 91 or better

 

I resurrected this thread because I filled my tank up today for the first time with 89-octane midgrade fuel instead of my usual 91-octane gas because I was totally shocked by the $2.95 per-gallon price of premium...but I regret it already.

Maybe it's just me, or maybe it's the car "detuning" itself, but I can definately tell a big difference in accelleration and general "sharpness" or performance without the added octane. I wish I had not been so quick to save the 10-cents a gallon difference.

Like so many have said, I bought a sports sedan...not a Honda Accord, and should feed it what it needs for optimum performance. Lesson learned. 'Nuff said.

 

Haha. In the first post of this thread says he says the price of premium was $2.25. In Overland Park, KS, the price today was $3.09 for premium I imagine I'll see $3.30-3.40 by the end of next week.