Murano, premium gas?


#1

I’ve seen conflicting reports about what kind of gas the Murano takes. One says premium and one says standard. Does anyone know which it is? And also, if they do recommend premium gas, what does it do to the car if you use standard? (Not saying I would, I’m just curious what the result would be.)


#2

I don’t know about those conflicting reports of yours, but the only true source of information is the owner’s manual. If it calls for premium gas, read carefully to see if it says required or recommended.


#3

Engines are tuned, by the engine design engineers, to use a certain octane fuel. They won’t run as well on other octanes; Forget about the wriggle words of “recommend” or “required”. Just look at the octane number, in the driver’s handbook, or manual, or fuel filler door, and use THAT for best performance.


#4

If you don’t use the proper fuel typically an engine delivers slightly less mileage offsetting any gains you think you achieve paying the meager $0.25/gallon are offset.

You may also incur engine damage and definitely degraded power.


#5

It may well bet that more than one engine was offered in that car maybe for different years. The real authority in this matter is the owner’s manual that came with the car. It also has a lot of other great information in it.

If it recommends premium, it means it will adjust for regular and not cause engine damage. However it will reduce power and mileage so you will not have the power you paid for and may not end up saving anything in fuel cost.

If it specifies premium and you use regular you can damage an expensive engine.

If it specifies regular, then using premium will cost you more, not improve mileage and could damage the engine.

Note: premium does not by nature have more power, or energy or additives than regular. It is just different.


#6

Chemically, premium fuel has a higher percentage of higher octane (longer carbon string length) hydrocarbons. The difference in power is obtained in the flash points. In an engine, to obtain more power, you must increase the amount of oxygen and fuel during a burn so that the piston is pushed down the entire length of the power stroke (there are other issues that modify this model, but are outside of this comment). One way to accomplish this is to use fuel that burns more slowly to push the piston all the way down. But as the burn rate slows (premium fuel), it becomes more difficult to ignite the mixture and burn it completely, so we raise the compression in the cylinder. But if we then put low octane (regular) fuel in a high compression cylinder, it will burn too quickly, causing a pre-ignition or premature explosion which occurs while the piston is coming up, before the piston is ready to push down. This is obviously counterproductive.

So modern engines use the computer to retard ignition timing to delay the spark when they sense pre-ignition to save the engine. But this in turn reduces the amount of available power because lower octane fuel still burns too quickly in a high compression engine and does not continue the burn to the bottom of the power stroke, thus wasting fuel.

Bottom line is to RTFM and follow recommendations. High octane fuel is needed in high compression engines in order to stand up to the higher cylinder pressures, to burn during the complete power stroke and to prevent long term engine damage from pre-ignition, even with computer safeguards. It is wasted in low compression engines because it will not burn completely, which will cause plug fouling and engine deposits over the long term.


#7

Thanks for all of the responses. I always wondered what the difference was. I don’t think I want a car that requires gas that is that much more expensive, so the search continues.


#8

Nissan says:

“Use regular unleaded fuel with 87 octane. For maximum power use premium fuel.”

I’d use premium (89 octane). You actually get your 240 HP that way, instead of a detuned whatever when you use regular.