Hey guys, I recently bought a Red Pearl 2009 G37x from my Aunt, it has 37K on it and is in perfect shape.


Anyway, I've had some time to drive it around a bit and the engine seems very coarse/loud (about 4000 RPM and higher) in the first two gears, more so in 1st. Enough so, that the AT Trans Shift **** button actually rattles. All other gears seem really smooth and refined feeling.


I'm planning on switching it to Penn Ultra this weekend, as I'm not sure what oil is currently in it. (she had it done at Jiffy Lube, so I'm assuming Penn 5w30 Dino oil)


The engine is super smooth at idle.


It has always run 93 octane it's entire life.

 

This engine is rough at cold idle, if that's what you mean. I had that same concern when I bought the car.

Also, it only requires 91 octane.

 

No, not idle, like WOT.

93 is Premium in the Midwest. We have 87,89 & 93

 

Well, that's all I got. Sorry, Joe. Lots of people complain about the diesel-like behavior at cold idle.

And that really sucks about you being forced to overpay for gas in your area. Sympathies.

 

I wouldn't shed too many tears. Remember, many of us Midwesterners pay less for 93 than Northeasterners and Californians pay for 87.

Now, back to the OP. If I'm reading your post correctly, the issue is engine coarseness above 4k, but only in 1st and 2nd gear, so if you go over 4k in 3rd everything is fine? Some NVH at high revs is one of the "standard" complaints about the G37's powertrain, but I've never heard about it being specific to certain gears.

 

And when it's actually cold out, cold idle is even worse (as I've been reminded of the past few days)

 

Here in CA, with our annoying fuel regs, I'd GLADLY pay more for 93. While 91 is listed as the minimum for higher compression cars sold in the States, it is by no means the most an engine can utilize. Turbos can benefit from ultra-high octane, all day long, provided they can keep the inter-cooler in the right zone. But even the G's 3.7 can make use of more octane, particularly when the whether gets hot and humid, as it does for so many of you in the summer months.

But regarding the OP's post about the engine...these Nissan power-plants have NEVER been known for their smooth, docile nature. Every time I start up our G, it feels like a Mack truck is turning over. Not entirely the most pleasant noise or feel. Also, at idle at stop lights, it's no better. Just the way it is.