hello all! I just leased a m35x and was wondering if it's ok to put in 87 or 89 octane gas. Will this damage the engine in any way? I believe the car manual said it was ok but was wondering about anyone else's experience with using the lower octane.

Thanks!!

I have been using 87 and works fine for me. I put 93 in the tank about every 4-5 fills.

I have heard that the lower octane causes the pistons to knock with engines that are designed to use higher octane. This knocking will cause engine issues.

Since your leasing, and if you want to take some chances you can try to get away with it - but the onboard computer can actually tell what octane your putting in, as it adjust performace and timming etc for the type of fuel; if you end up with engine issues you may have to end up paying for them, and they will have document proof;

The differance in costs here is Canada is about $5 CAD for each tank, not sure if its worth the risks for that kinda cash - considering the cost of the car, it seems really odd that this is an issue for you

p.s. you will get better mpg with the right fuel, that being the 91/92 octane...tk

Well here is some text that talk about this:Why use High-Octane FuelA direct quote from Stone (p. 80): "The attraction of high octane fuels is that they enable high compression ratios to be used. Higher compression ratios give increased power output and improved economy [assuming the same power of engine] ... The octane number requirements for a given compression ratio vary widely, but typically a compression ratio of 7.5 requires 85 octane fuel, while a compression ratio of 10.0 requires 100 octane fuel. There are even wide variations in octane number requirements between supposedly identical engines."

Raising the octane level of your fuel will primarily help prevent knock. If your engine is not currently knocking, you won't see any significant advantages of using higher octane fuel. On the other hand, if the engine is designed from the beginning for higher octane fuel, it will have considerable advantages in power and economy.

WEBSITE:http://www.stanford.edu/~bmoses/knock.html

More:Knocking Harmful? Occasional light knocking or pinging won’t harm your engine, and doesn’t indicate a need for higher octane. But don’t ignore severe knocking. A heavy or persistent knock can lead to engine damage.

WEBSITE:http://autorepair.about.com/od...a.htm

More Data:http://www.citgo.com/Products/...sp#Q3

In a nut shell, google engine knock and you will get the whole deal; Octane rating and engine knock show up together in ALL the searches I did;

I wouldnt bother trying the lower octane gas... not worth the risk, but the choice is yours;tk

Another site:http://www.straightdope.com/columns/041008.html

Its a few years old, but it has some usefull things in it...

another great link:http://www.state.mn.us/mn/exte...s.pdf

I guess I've made a point...tk

Under the new rules [buy any oil you can get] refiners are adhering to absolute minimal addition of deposit control additives to save a few pennies.

What premium buys you now is just more additives than regular.......often the octane ratings are less than honest in any grade since there is no state of federal testing requirements.

Absolutely no requirements that what octane is posted on the pump is true!

If the Infiniti Manual says its Ok. I would assume its OK. I have not noticed a difference in anything from the octane I put in the car.

Yes, the M45 can compensate for regular, non-premium, gas. But, you are stressing the engine somewhat, and even the minute, low-level, pings have some effect on an engine that is tuned for premium.

On the other hand, the M35 with the VQ35DE, has a minimum of 87, albeit it recommends using premium at 91. See the quote below for the extract from the Owners Manual.

By the way, as Dennis (Q45tech) mentions, the quality at the gas station simply may not be as good as you would want. So, bad gas is a strong possibility ... and you may end up with less than an effective 87 gas as a result!

Also, for most people and their uses, keep in mind that the cost of using premium 91 over regular 89 or 87 is such that you might spend an extra $10 - 15 or so each month. In an M45, I would not consider this a useful amount to be worth it! So, I would follow the "use 91" rule.

In an M35, the question is murkier - I can see where some people would simply go by the Owners Manual recommendation and use regular. Personally, I would consider using 91 for the following reason.

I would point to the experience we have with my wife's 1997 Acura 2.2CL. The manual says to use 86 or 87 gas. Yet, I have found from personal measured experience that using 91 gives me better gas mileage ... more than offsetting the cost differential of $0.20 per gallon on a $2.60/gallon base cost.

As a result, the 91 octane is cheaper per mile surprisingly. After I showed this result to my wife (she checked it herself too!) she has stopped complaining about the fact that I put Premium in her car "when it does not need it!"

Infiniti M Owner's Manual wrote:VK45DE engine

In order to maintain engine and exhaust system durability and performance, unleaded premium gasoline with an octane rating of at least 91 AKI (Anti-Knock Index) number (Research octane number 96) must be used.

If premium gasoline is not available, unleaded regular gasoline with an octane rating of 87 AKI number (Research octane number 91) may be temporarily used, but only under the following precautions:

Have the fuel tank filled only partially with unleaded regular gasoline, and fill up with unleaded premium gasoline as soon as possible.

Avoid full throttle driving and abrupt acceleration.

VQ35DE engine

Use unleaded regular gasoline with an octane rating of at least 87 AKI (Anti-Knock Index) number (Research octane number 91). For improved vehicle performance, INFINITI recommends the use of unleaded premium gasoline with an octane rating of at least 91 AKI number (Research octane number 96).

First, welcome to the forum.

Second, love your car and put the good stuff in it. There's plenty of debate but think of it as if it was your kid. Would your kid do better in school on pop tarts or vegies and fruits?

With the up coming RFG change out to 10% Ethanol [for MTBE] expect some real strange mixtures to start becoming available. Intentional or not!

Always refill at the coldest time of day and try to always keep a half tank to minimize the water amount vs gasoline in your tank!

Be sure to take appropriate measure to frequently dewater your gasoline tank........check for rust and corrosion. FREQUENT FUEL FILTER CHANGES!

The warranty does not cover buying defective gasoline you will have to sue the station involved and the terminal and the refiner.

Don't believe I'm being ALARMIST.

on the 1/2 tank thing, most fuel pumps use the gas itself to cool the fule pump, if you always run at empty, the pump overheats, and that a few $1000 to replace...tk