Do you use premium fuel? (Infiniti M)

[mindovermatter81]

So far I've only put premium fuel in my M, but I was wondering what the benefits of doing this are, or if it even matters to do so.

[Mark Linkous]

Hello,It seems most if not all members of this forum use premium unleaded. Speaking for myself, I have never not used premium. The engine is designed for premium unleaded. While regular will work, it is at the cost of performance. The engine computer will compensate for the lower octane, but, engines that specify premium usually have higher compression ratios requiring such to perform optimally. Sadly, I would guess that most who leased this car new would go the el cheapo route. When you know you are not going to be keeping a car past a few years, most do not care. Cheers,M.L

[szh]

With the M45, Premium fuel is required. With the M35, it is strongly recommended.

1. Technically speaking, putting 87 or 89 into the M45 will probably not damage the engine, particularly if you have no choice (premium was out and you are on the highway on a trip running out of gas! ).

However, the engine management unit is now compensating for the lowered octane, the knock sensors are working overtime, and you are probably getting some low-level pinging (which you may not hear, but this is not helping your engine).

2. The cost difference between 87 and 91 in California is about $0.20 a gallon - a small percentage of the total cost per gallon - and this probably similar in other parts of the country. For most people, and their monthly driving miles, this is probably a $10 to $20 difference in monthly operating cost.

If this is a problem financially for a given M owner, then the act of buying a relatively expensive car is somewhat of a questionable financial decision for that person. You should consider changing to a more affordable car.

Note that this is absolutely not meant to be pejorative - just an objective note that sometimes it is way better to take a deep breath and make a financially sound decision when buying a car. Don't overdo it with falling in love with a particular car or brand or model!

I say exactly the opposite for house mortgages typically ... car's depreciate, houses mostly do not. My advice: "buy more house than you can afford - your income will catch up; but buy less car than you can afford - it will all go away over time".

Hope that helps!

Z

[mindovermatter81]

Thank you for you response, I will continue to use the best fuel possible, probably Chevron or Shell Premium.

[szh]

Thank you for you response, I will continue to use the best fuel possible, probably Chevron or Shell Premium.

Good choices!

Particularly the Chevron ... its Techron additive is a good idea.

Periodically, every 3000 to 4000 miles or so, you should also do a BG-44K gas treatment - add a can to the fuel tank, fill it up and drive (take a long trip if you can, but this is not strictly necessary). Best time to do it is about 300 to 400 miles before an oil and filter change. Costs about $10 to $15 per 11oz can on eBay (I buy them four to six cans at a time to optimize the shipping cost). BG-44K is the basically the same material as the Chevron Techron additive - just more concentrated for a good injector clean!

If you do not push the engine on a 2003 or 2004 M45, the VK45 engine can develop carbon deposits - the typical sound is a rattling, pinging noise from the engine. The BG-44K, as well as nice hard driving, is a good way to reduce/prevent this from happening! Lots of fun too.

Z

[MagicM]

Premium all the way, why try and save a few cents per liter.

[M45-Zero260]

I agree. When I was a teenager, the difference between regular and premium was over 20%. Now, it's around....5%...not even? I figure that I'm driving a car that started out over $50k...I'm going to treat it as such. I only use Mobil 1 oil and filter, stock parts, tires, premium gas, etc. There were only around 7,000 of these beasts imported to the USA in 2 model years, treat it like you are driving a living legend. Seriously, when you are driving around, how many cars of your same make/model/year do you see? I can count on ONE hand in the past 2 years how many I've seen. Don't skimp on the gas. How would you feel if you were craving an ice cold Corona with lime, and your friend offered you a room temperature Pabst Blue Ribbon in a can.

[jgoodman]

I asked the same question on this forum about 6 months ago. I was running regular in my M35X and it didn't seem to suffer any performance loss. However, a few months later, my check engine light came on and when I took it to the dealer, they replaced the throttle body under warranty. It had a lot of carbon built up on it. I bought the car used and it had been owned previously by a rental car company. I'll bet it didn't see premium fuel very often. I think between the the previous owner and me running regular in it, we succeeded in causing the carbon build-up. Since I got the throttle body replaced, I only run premium in it and it definitely runs better. The throttle response is definitely quicker, probably because the computer is not retarding the ignition to prevent knock.

[infinitedrift]

I always run 93 Octane(FL) even in my girls 03 Maxima, but there is a Sunoco here that sells race fuel at 103 octane what do you think would happen if that was tried....

[szh]

Probably not much actually, with 103. Law of diminishing returns.

Using 93 is way good enough, since the M45 engine is optimized for good performance with 91 to 93.

But ... it won't hurt to try 103, I'd think. So, let us know what you see with it.

Z

[MagicM]

Probably be completely wasting your money on 103, octane = energy required to ignite, not how much it gives off. Unless you have some high performance 20,000 rpm redline 800 horsepower engine, total waste of money.
Modified by MagicM at 10:57 PM 11/11/2007

[mindovermatter81]

How would you feel if you were craving an ice cold Corona with lime, and your friend offered you a room temperature Pabst Blue Ribbon in a can.

Haha, I would hate to get a Pabst Blue Ribbon!

[paulc]

Magic M's comments are right on. The octane rating of a fuel describes it's anti-knock characteristics, not the energy contained in the fuel. Here is part of the explanation of octane ratings that can find in wikipedia...

"The power output of an engine depends on the energy content of its fuel, and this bears no simple relationship to the octane rating. A common understanding that may apply in only limited circumstances amongst petrol consumers is that adding a higher octane fuel to a vehicle's engine will increase its performance and/or lessen its fuel consumption; this may be false under most conditions — while engines perform best when using fuel with the octane rating for which they were designed and any increase in performance by using a fuel with a different octane rating is minimal or even imaginary, unless there are carbon hotspots, fuel injector clogging or other conditions that may cause a lean situation that can cause knocking that are more common in high mileage vehicles, which would cause modern cars to retard timing thus leading to a loss of both responsiveness and fuel economy."