I understand that people will say you bought a premium car put premium fuel. I'm like everyone hate paying more. So if I lose 15HP by using regular I would be fine. I do not notice a difference. It seems to run normal under 1/4 throttle to 3/4 and once at full.

Please if your reply or answer is just an opinion please don't respond. I'm looking for first hand knowledge.

My curiosity is that if the knock sensor and computer recalibrate for different octane why would it matter besides not getting 300HP but 290HP.

2nd. If we are slowing the timing and Knock sensor and computer are doing their job. Why do people say they get less gas MPG. To me if everything slows and runs why would it waste gas?

 

Report back after you have put in 2 or 3 fill up of 87 octane gasoline. Let us know how your car runs, and if you get any spark knock.

 

Ok. Why would it change. Figured it would kick and sputter when computer and knock sensor is looking for premium.

 

The car will run fine on regular. Save your money. =>7500 Regular gassed miles traveled in the flatlands and the Rockies, and the car does not knock, is faster than my 2010 Max. 33 MPG! open road cruising.

 

Robtroxel sees this pretty much as I do. As long as the car can differentiate between octanes and adjust to what you put in the tank, the primary loss by using regular gas is at the top end of the performance spectrum, and NOT a loss of fuel efficiency.

 

Can someone explain to me what "top performance" means? When does the car need it? Accelerating from a stop? Doing 100Mph on the highway? Doing 100MPH going uphill?
Is it just a matter of high RPMs?

 

'Top performance' when discussing octane is generally referring to acceleration. That can be from a standstill or when accelerating at any speed or when climbing a hill, etc. 'Top performance' is not referring to handling, braking, top speed, etc. It is referring to a tad of extra oomph at the top of the power band, normally in play only when we are accelerating at or near maximum power. For me, I would seldom reach that point. Maybe when passing with a very short passing lane or speeding up quickly on a short uphill entrance ramp in order to merge with freeway traffic or passing while going up a hill. This will normally be at high RPMs, but, with the CVT, RPMs do not always compare directly with speed.

 

In tuning another car with a flashed ECU, advancing the timing under light throttle cruising supposedly improved highway mpg. Using the advanced timing beyond stock parameters required premium fuel. With the maxima, if lower octane limits the ability for the ecu to advance timing during cruise, I could see it hurting fuel efficiency.

 

I use ONLY 87 octane and see no performance drop. This after 6000 miles of driving. I don't race or abuse the car at all. No performance drop that I can see.

 

I'm pretty cheap, and from personal experience, the only time there is a big difference in regular and premium gas (other than the money) is when the car's computer and sensors tries to be fancy with it. For my first thousand miles I used premium and in the 4000 miles after I've used 87 octane and can not tell any difference. It's still got plenty of pep and gas mileage seems about the same, 32-33 on highway.

 

Nah, it wouldn't sputter, idle rough, buck etc. The ECU will adjust.

Within the ECU ROM are Spark advance tables, specifically two, High Octane (higher ignition advance ) and Low Octane (lower ignition advance). There are additonal spark multipliers too for IAT, ECT and so on. While i have not viewed a Maxima ROM, it should be similar.

In any case, when a knock sensor picks up noise at a specific frequency, depending on how much and for how long, the ECU will interpolate between the two octane tables. e.g retard ignition advance timing as needed until noise is gone. Sometimes, you cannot even hear it.

The VQ 3.5 compression ratio is ~10.6 hence the recommendation for 91 or higher octane. Sure filling up and driving around with 87 octane will be fine but throttle response, HP and torque will be affected. Driving around in sport mode with the ramped up throttle rate should minimize this affect.

For long periods of driving with 87 octane and eventually switching back to 91 or higher, I'd reset the ECU (disconnect and reconnect the battery after a few minutes) as this should force the ECU to go back to the High Octane table.

 

Is the high octane recommended or required...

 

It's recommend. Inside the fuel door, there's a white decal which reads "Premium fuel recommend...."

 

Just curious if you all have considered the total annual cost for premium to determine if it's worth it. Suppose you drive 15000 miles a year and average 25 miles per gallon. If you pay 25 cents more for premium per gallon, that's only $150 more per year. Seems like a no brainer to me to spend a little extra to go with what Nissan recommends, especially on a 40k car.

 

I appreciate dcpatters contribution to this topic. The following might make it easier for some.

A few years ago, when I was not so patiently waiting for the 8th gen, I was investigating the Hyundai Genesis, which was offered with a 3.8 V6 or a 5.0 V8. It now appears they are offering just the V6 in the Genesis, and the V8 in the Equus. Below is the link to the specs page for the 2016 Equus. If you open the Mechanical section, you will see that they rate the V8 at 429HP**. When you scroll down to the bottom, you will see that the double asterisk offers the qualifier that the 429 HP is based on premium fuel being used. It should be noted that the compression ratio of the Tau V8 is 11.5/1 (higher than the Maxima).

https://www.hyundaiusa.com/equus/specifications.aspx

I then downloaded the owner's manual for the 2015 Genesis, when they still offered both the V6 and V8. Below I copied and pasted the section from "Fuel requirements."

3.8 engine
Your new vehicle is designed to use
only unleaded fuel having an octane
number ((R+M)/2) of 87 (Research
Octane Number 91) or higher.

5.0 engine
Your new vehicle is designed to use
only unleaded fuel having an octane
number ((R+M)/2) of 87 (Research
Octane Number 91) or higher. For
improved vehicle performance, premium
unleaded fuel with an octane
number ((R+M)/2) of 91 (Research
Octane Number 96) or higher is recommended.

I think this would have been a less confusing way to suggest fuel usage for the Maxima. I also agree that most of us will never push our cars hard enough to realize the increased performance that premium offers. That being said, I usually put premium in my tank, even though I fully understand it likely offers ME no benefit.

 

I have always thought of my car as a lady. Treat her nice and she'll be thankful. A nice wash and she always seems to ride just a little bit better than before. So she gets the premium gas and as I read about Formula One drivers to add a bit of sherry to the tank on race day. Though my young lady prefers Irish whiskey.

 

Nothing but chevron 91 thats my best results for me !!