During my pre purchase inspection, the Infiniti mechanic, said that the previous owner of my G didn't use premium gas ALL the time, he advised a $299 fuel system flush.... which leads to my question...which fuel additives are best for the G37? if any.

 

That Infiniti mechanic is either an idiot or just blowing smoke up your ***. That car doesn't need a fuel system flush. Low octane gas is just low octane gas, it's not any cleaner or dirtier than premium gas.

As for fuel additives, they're all bs. Save your money.

 

Completely correct. You don't need to use any fuel additives. If you want to flush your fuel system buy a couple of cans of Seafoam for $20. You can use it in the fuel tank to clean the lines, sucked directly into vacuum hoses to clean the top end of your engine, and in the oil just before an oil change to clean the bottom end. All of this is optional, not necessary. And certainly not $300.

 

There's no way for the mechanic to know what grade of fuel was used. The current tank can be tested to figure out what it is, but not previous tanks. Octane rating has absolutely nothing to do with the addatives used in the fuel. Lower octane rated fuel won't leave any kind of deposit that a higher octane fuel won't. Plain and simple, the "mechanic" lied to you to get you to pay more money.

If you like, give the car a seafoam treatment. I do it to all of my vehicles as part of an initial cleaning. (I buy used vehicles since it's far more economical) If you're worried about one treatment not working, do two, or three, or five. It's about 8 bucks a can (let's make it 10 for ease of math) and you need two cans per treatment, so it's $20 per treatment. Way less than $300 and the best cleaning you can get short of taking the engine apart and physically cleaning the internals manually.

 

+1 on seafoam. Haven't used it on my car yet but I have use it on my previous cars. Make sure you're on a well ventilated area if you're gonna stick a vacuum hose inside the can. There will be LOTS of smoke for a while so don't freak out, that's absolutely normal. Also it could be handy to have someone help you by modulating the gas pedal since the engine might stall when it's sucking the seafoam.

 

There's some truth to that statement, premium fuels, besides their higher resistance to knocking, contain more cleaning additives than regular octane fuels.

 

That's a marketing trick. The margin of error is higher than the difference between the two grades. Trust me, there's no significant difference.

This is how it works (percentages are completely fabricated)
Regular fuel = .5% additive and 99.5% fuel.
Premium fuel = .6% additive and 99.4% fuel.
Yay Premium has more additives!

Note how the percentage of fuel drops as detergents go up. Profit margin on fuels is way higher than the profit margin on detergents. Do you really think any company is going to throw away profit when you're going to buy their product anyway?

 

I knew it was some BS, but I figured he had a way or found some carbon build up on a fuel part he may have checked. I've used seafoam in my Tahoe before, works great too. well in that case im sure its ok, I may do a seafoam treatment just to be sure. Thanks!

 

^^ This.

The only significant difference in between regular and premium fuel is the amount of toluene in it. Yes toluene, the same toluene you can buy at home depot.

 

Use the recommended octane rating of fuel!!! Read about octane ratings on wikipedia and learn why.

Octane rating - Wikipedia, the free encyclopedia

It's not just some marketing ploy to get you to buy higher octane fuels. In fact, it's quite the opposite. People believe they are getting better performance out of their gasoline by getting a higher octane than needed for their engines. If you run a lower octane gasoline in your car that requires a higher octane, your engine will have a rough idle and will be prone to pre-ignition under load. NOT A GOOD THING!

Also, don't use any additives in any gas or oil. Now THAT is a marketing ploy.

Another point, you can tell by looking at the spark plugs if pre-ignition has occurred or is occurring.

Reading Spark Plugs Correctly

Let the flaming begin...

 

You should do more research. Neither of those websites are trustworthy. The fact that you believe what you read on wikipedia means that even if I go into the technical details of octane ratings and heat of compression and knock and how they interact, you wouldn't understand it.

 

Techron concentrated EFI cleaner or Toyota EFI cleaner. If you use the Toyota stuff, add it to 1/2 tank of fuel and burn the fuel off within 1-2 days. It is really strong and you don't want it in the system any longer than necessary.

 

The dealership is trying to get more money, as always. This issue is not significant enough to matter. The 0.1% difference won't harm you car. Use Premium on it and you'll be fine. Don't waste $300.

 

Is this better?
The Low-Down on High Octane Gasoline
Oh and guess what: same info. But wait, you'll tell me the FTC isn't a reliable source either.

Just because you can spout off things like compression and octane rating, knocking, pinging, pre-ignition, pre-detonation etc. doesn't mean I can't do the same. In any case, you can run lower octane fuel in your car if you want. I was just putting out my advice. Misinformation is being spread about gasoline and octane ratings and I wanted to put in my 2 cents about it. If you don't like it fine. You won't hurt my feelings.

 

From Denso Iridium

Pre-Ignition- A melted or burned center and/or ground electrode, blistered insulator and aluminum or other metallic deposits on the insulator
Symptoms: Loss of power causing engine damage, Pre-ignition occurs when combustion begins before the timed spark occurs.
Causes: Plug insufficiently tightened, Engine insufficiently cooled, Ignition timing too advanced, Plug heat range too hot