Common Octane Usage

[DanTheMan]

Are any of you folks using higher octane, >87? I filled up with premium, 91 octane, and have noticed a 2 mpg increase in mileage. Someone told me to reset the ECM for better results. I'm not sure I want to do all of that, maybe just disconnect the battery...... I have run higher octane in other vehicles without any difference. I am surprised in the difference in the Rogue.

[philipa_240sx]

I would be sure you are not calculating it wrong. Also try another tank of regular 87 octane and see if you can repeat the better mileage numbers you are seeing.

[DanTheMan]

So far, I have several months worth of 87 octane to go off of. I will be filling up again next week. I will verify the mileage again. So far, there definitely is a difference.

[philipa_240sx]

I would run through at least 2-3 tanks on each fuel to do a decent comparison. We are seeing considerable changes in weather lately and it does have an impact on fuel economy. Typically in Canada, we notice a 2-3 mpg decrease during winter months. This is partly due to winter gas formulations, increased idling, and colder temps.

Generally, you will never notice and increase in fuel economy that can be attributed to using higher octane fuel. It is usually due to other factors.

[zakmartin]

Unless your engine is specifically designed to run on higher octane fuel (which the Rogue is not), then there is no improvement in power or fuel efficiency by using premium gas as opposed to regular. As Phillipa stated above, there are likely other factors contributing to your improved mileage.

Around this time of year, gas stations change over from their winter blends, which are high in ethanol, to their summer blends, which tend to improve mileage due to thier lower ethanol content. My guess is that this has something to do with the better MPG/KPL you're currently experiencing.

You should stop wasting your money by buying fuel with an octane level that your car can't use.

[ahhbeebee]

So far, I have several months worth of 87 octane to go off of. I will be filling up again next week. I will verify the mileage again. So far, there definitely is a difference.

Engine starting to break-in? I noticed you are driving a 2010, what's the total mileage on the vehicle? I didn't start getting my best gas mileage until reaching about 3000-5000 miles on the engine, many people have been reporting much longer engine break-in times.

[nitsudima]

I have read, although I don't have any URLs handy, that using gas with higher octane than the engine was designed for also increases harmful emissions. Higher octane gas is made to be used in engines with higher compression ratios, so perhaps in engines designed for 87 octane the burn isn't complete when using 89 or higher octane gas, thus resulting in different emissions.

Just a guess from a non-engineer who can't find a link to the article he's remembering...

[maverick_rogue]

This URL provides similar info. i.e. Higher Octane is bad for environment.

http://www.slate.com/id/2182076/

I used to use Higher Octane gas but have recently switched back to normal 87 Octane, wanted to go green.

But yes, I had + 2 MPG increase and engine used to run quieter. It defies logic though since higher Octane should mean higher burning point and higher C.R. May be Calorific Value of High Octane Gas is higher than the normal one. Not sure though.

[zakmartin]

Nicoclub, who sponsors this site, has a really good write-up about the myths surrounding octane levels.

Here's the link:http://www.nicoclub.com/archiv....html

[philipa_240sx]

Nicoclub, who sponsors this site

We don't sponsor the site... it's ours! But thanks for pointing out the article!

Anyway, octane levels do have a small effect on your vehicle's operation. Here's why:

All modern Nissan engines incorporate a very sensitive knock or pre-ignition sensor. When any pre-ignition is detected, the ECU temporarily retards the ignition timing until the pre-ignition stops. Retarding the ignition timing also results in reduced power. However, since it's only temporary you usually will never notice it. Sometimes it's beneficial to use a higher octane fuel... ie. when towing heavy loads or hauling cargo... especially in hot conditions. It can prevent engine damaging detonation and can possibly give you a small power boost as the ECU won't retard the timing due to less pre-ignition.

When I used to race, we only used premium fuel... 91 or higher... for the same reason I explained above. I doubt any of you Rogue owners would try to race your vehicle on the track... but it's not the first time I've seen an SUV or pickup out there trying!