KLB

I'd like to hear his explanation for how that supposedly works.

B L U E S L A T E

iTrader: (2)

Unfortunately SoCal doesn't offer 93 Octane gas. :/

B L U E S L A T E

iTrader: (2)

That is FOS.

jb606

Let's see if this makes sense...The ECU controls when and how much FUEL to inject and it also signals when to fire off the spark plugs. Where does oil come in to this equation? You might want to look around for a different group of people to work on your car.

If I'm missing something please educate.

Amon_Ra

I've been between Shell and BP since getting this car...honestly dont know which one i get better mileage from...if there is a difference its very small to say the least

spect2k

http://www.toptiergas.com/

Check it out, there is a lot of useful information on there. I can't tell you what gas not to use, but it helps you to make a goos choice when you're on the road. Perhaps this explains why shell is a bit more pricey than most.

328HP

So, after reading that Shell 93 is better than any other 93 I decided to try it for myself. This is my first week trying it, regular commute and by Friday I would normally be on a 1/4 tank, I am at half a tank today.

I will only use Shell 93, thanks for the tip

Austin713

also look at the Ethanol content in the gas. this will greatly decrease gas mileage and can be harmful to your car. most places in texas have a 10% content, but i have been noticing that valero now runs 15% at some places. We get 93 here in texas, nothing but. i normally fill up at HEB because its right by my work and the cheapest, if im on a roadtrip or something its Shell or Chevron without a doubt

MaluG37

Shell is a great gas. I've used it in all my cars. Right now I'm running BP or Exxon since they are running discounted rates on Monday, Tuesday and Thursday. Can't pass that up. But if price wasn't a factor it would be 93 Shell V-Power.

Amon_Ra

I drove 15 mins to a shell which is the cheapest gas in my area...surprisingly...If this tank makes it the entire week I'll use shell exclusively from now on lol

JohnEnglish

hahahaha

twin_snails

iTrader: (2)

For the record, the VQ37VHR engine uses an 11.0:1 compression ratio which is higher than that of the VQ35DE.

Simple solution is just fill it with 93 octane from your preferred station and call it good. Is it really with saving 5 bucks a week at the expense of your engine?

I knew a guy that ran 87 in his G35 Coupe ('04 model). He started getting pinging. Then the dealer recommended switching to 93 exclusively. It even pinged on 93 octane gas. The dealer insisted that even on 93 octane that this was normal behavior in the VQ35DE. Notice on the redesign with the VQ37VHR, you'll see that Nissan/Infiniti raised the compression ratio (more heat to dissipate) and significantly reworked the water jacketing around the cylinders and heads for improved cooling capability (Read: less ping).

So, don't chance your $40k + investment to save a few bucks and get crappy performance out of it. Sure, some get away just fine on 87 but I'm sure there are a lot of us who like to tip deep into the throttle on occasion and at that point, the problems with running 87 octane become glaringly obvious.

93 Octane or highest grade in your area FTW!

danno62

Hey, I understand what you are saying. My G37 was having an issue with the drivers electric seat motor. So the dealer told me to change the air filters every one hundred miles to fix it. Changing them tomorrow...wish me luck. GEE!

twin_snails

iTrader: (2)

If you're saying that lower (87) octane gas burns hotter than premium (93), that would be misleading an incorrect. If 87 octane burned hotter, it would yield more power as it produces more BTU's of thermal output.

Octane is simply a rating of a gasoline's ability to resist detonation (ping) under compression. See Wikipedia's explanation of this:

"Higher octane ratings correlate to higher activation energies. Activation energy is the amount of energy necessary to start a chemical reaction. Since higher octane fuels have higher activation energies, it is less likely that a given compression will cause autoignition.

It might seem odd that fuels with higher octane ratings are used in more powerful engines, since such fuels ignite less easily. However, an uncontrolled ignition is not desired in a spark ignition engine.

A fuel with a higher octane rating can be run at a higher compression ratio without causing detonation. Compression is directly related to power and to thermodynamic efficiency (see engine tuning), so engines that require higher octane usually deliver more motive power and do more work for a given BTU or calorie of fuel. Engine power is a function of the fuel, as well as the engine design, and is related to octane rating of the fuel. Power is limited by the maximum amount of fuel-air mixture that can be forced into the combustion chamber. When the throttle is partially open, only a small fraction of the total available power is produced because the manifold is operating at pressures far below atmospheric. In this case, the octane requirement is far lower than when the throttle is opened fully and the manifold pressure increases to atmospheric pressure, or higher in the case of supercharged or turbocharged engines.

Many high-performance engines are designed to operate with a high maximum compression, and thus demand high-octane premium gasoline. A common misconception is that power output or fuel mileage can be improved by burning higher octane fuel than a particular engine was designed for. The power output of an engine depends in part on the energy density of its fuel, but similar fuels with different octane ratings have similar density. Since switching to a higher octane fuel does not add any more hydrocarbon content or oxygen, the engine cannot produce more power.

However, burning fuel with a lower octane rating than required by the engine often reduces power output and efficiency one way or another. If the engine begins to detonate, that reduces power and efficiency for the reasons stated above. Many modern car engines feature a knock sensor – a small piezoelectric microphone which detects knock, and then sends a signal to the engine control unit to retard the ignition timing. Retarding the ignition timing reduces the tendency to detonate, but also reduces power output and fuel efficiency.

Most fuel stations have two storage tanks (even those offering 3 or 4 octane levels), and you are given a mixture of the higher and lower octane fuel. Purchasing premium simply means more fuel from the higher octane tank; the detergents in the fuel are often the same."

JohnEnglish

Yup. I think the confusion is coming from the fact that high compression engines have a hotter burn, but it doesn't have anything to do with the octane itself, it's just the nature of a high compression engine.