si_driver

The gas station was out of 93 octane yesterday, so I pumped 89 instead.

After a few miles I thought something was wrong with the car.

It really makes a big difference on this car going from 93 to 89.. Never again if I can help it.

On the old G35, which I still have too, it did not make such a big difference, but on the G37 it's almost day and night.

takeapieandrun

iTrader: (2)

I wish we got 93 in Communist-fornia. Even worse is the 10% ethanol blend.

blnewt

iTrader: (13)

We have one station in town that has 91 Octane, all the others have 90 max and all use Ethacrap, at least most of the year now

p0on

yup, even 91 Octane "Premium" gas as specified in the manual is not enough. Hesitation below 3k rpm on warm days

Epiphany

You guys should come live somewhere with a high elevation, 91 is useless unless you're FI here. 89 is all it takes.

Rochester

iTrader: (8)

The VQ37HR is designed to run optimally with 91 octane. Please read page 9-4 in your Owner's Manual. If you use gas with a lower octane rating, then you run the (minimal) risk of engine knocking and reduced efficiency which can be interpreted as having a sluggish response in the throttle. If you use gas with higher octane levels, then you simply waste your money. Do not use E-85, and avoid Ethanol blends if you can, but don't freak out about it as long as the Octane rating is >= 91.

Higher octane gas is not Liquid Swartz. However, in many areas, 91 octane isn't available, making 93 octane your only option... so that's what you use. It will neither hurt nor help. Stations that decide to only offer 87/89/93 Octane gas do so based on market demand and simple profit, because they can ask highway robbery prices for 93.

This isn't rocket science, people. Please stop second-guessing mechanical engineering with faith-based decisions, you silly flat-earthers. LOL

Tech 101 ? Octane: the facts and the fiction behind those higher-priced fuels | Hemmings Daily

si_driver

Rochester..

you are right on the 91 octane thing and 93 is a waste. However, in my case I advanced the timing by 2 deg. on my car and I can see that even on 91 the car doesn't feel as quick and responsive as with 93.

Rochester

iTrader: (8)

That's interesting. I remember how that was something people do with the VQ35, as high-rpm power loss sacrificed for low-end gains, but haven't come across that yet for our engine. Truth is, I've not researched this even a little bit for the VQ37. I assumed timing issues in this car were more static because of the VVEL design.

Got any links that discuss this?

si_driver

Rochester,

my car felt sluggish and slow for some reason when I bought it (used) 2012 G37xS. Compared it to my old 2003 G35 with 250,000 miles and the G35 felt quicker. A lot of it probably has something to do with the transmission being 5 vs 7 speed and RWD vs AWD.

I tried checking the obvious things first like air filter, etc. Clean the throttle bodies (but I already knew it wouldn't do much because of the VVL system really takes care of all air flow).

So I had still no improvement in the way the G37 felt - slow. As I have the autoenginuity scan tool, I used it to adv. the timing by 2 deg. Now the car felt much better. The engine is more responsive and when hitting the gas pedal hard the initial surge is much harder and better than before the 2 deg change but it does feel way slower and less responsive if I don't use 93 octane gas.

I have not read much about this and can't point you to any direct posts. But assuming that I did change the timing it would make sense that using 93 octane gas is probably better than 91 or 89..

Rochester

iTrader: (8)

Yep. I would think that too. I didn't know you could advance/retard the timing on our cars without asking the dealership/shop to perform the work. But this is pretty interesting. Thanks!

https://www.autoenginuity.com/produc...niti-ei06.html

Personally, I think low-to-mid range gains are lots more enjoyable than high-RPM horsepower. I give you credit for experimenting. IIRC, bumping from 15* to 17* was a fairly common practice with the 5.5 Gen Maxima.

Just this morning, I'm not really finding a lot of info on advancing timing for our engines. Found this post over on the Z forum, with a copy & paste from someone at UpRev:

http://www.the370z.com/tuning/36746-...ml#post1123935

blueis300

iTrader: (1)

Is that just what the dealer can do the the Tech II tool? I did that when I had my Maxima.

si_driver

I love the autoeng. tool. It can do almost everything that the Consult tool can that the dealers use.

I have had it for many years since I bought the G35 and have never been to the dealer for any work as I can troubleshoot and fix my own car with it.

The autoeng. scanner can adjust the timing by 2 deg. either up or down...

telcoman

I tried 93 for one month with my previous 06 G35
Aside from the added cost my MPG dropped so I went back to using 87
My current 2012 G37S has never seen a drop of 93
I only use 87 and it runs fine with good MPG
I mainly purchase my gas here with excellent results



At a $.43 cent a gallon difference in price it is a waste of money in my opinion

Telcoman

blueis300

iTrader: (1)

I put 87 in once by accident and will never do it again. Car was a dog and mpg suffered.

si_driver

Sure it will run fine, mine runs fine too. But it is slower and driving it hard I can feel and see the difference on the G37.

On the G35 I started using the cheapest gas I could find once I was at 30,000 miles. 220,000 miles later and I still use the cheapest and the car runs fine.. I don't feel much difference on different octane levels on the G35, but on the G37 it makes a big difference in how to car responds and runs, at least after I changed the timing to +2 deg.