In case there is anyone who's interested, I thought I would take the time to relate the results of some octane testing that I've done with my 2012 MO over the past three months. I've owned the car since January 2012.
I did a search on the forum, so I know that many folks have had concerns about the octane needs of the MO, especially after Nissan lowered the requirement from Premium "91" down to Regular "87". My summary of those postings is that you'll see some people who believe certain things and some people who know certain things. The believers, heaven bless them, believe. On the other hand, the knowers, well, they know. There is a big difference in fact, although the believers will say otherwise (i.e., "you're wrong--the MO will not benefit from high octane gas because my Toyota Camry doesn't and so that proves it"). The reason I have related this summation will become apparent in a moment.
But before I tell my story, I'd like to request: 1) if you don't care about or don't believe my test results, please don't flame me. 2) If you think that you know better than me (i.e., you think you "know how the MO engine is designed" so what I report "can't be true"), just accept that your world view is what it is and please don't flame me. 3) Please don't flame me.
OK. Here's my story. I have found that running 91 octane, the highest available in my area, versus running 85 or 87 octane (the regular and mid-grade choices) makes a big difference in my MO. I get better mileage with premium (1-2 mpg) and the increased off-the-line performance is, well, amazingly better. I tested this "theory" over 6 full tanks of gas (at least 18 gallons of regular, premium, and mid-grade, average miles per tank, 310). That's almost 2000 miles during the hot time of the year (A/C running all the time, average temperature 92 degrees, relative humidity range 30 to 45%, altitude about 4500 ft). Fuel purchased at the same station at the same pump at the same time of day. No mixing of grades; at least 18 gallons of fresh gas per tank. Tire pressures checked at each tank fill. No extra cargo kept in car. Driver alone 75% of the time for each tank, with one passenger about 25% of the time.
Yes...I kept careful records. And here's some "fine print" for anyone who's really technically minded: miles at start of test = 3570; miles at end of test = 5550. Yes, I know, my engine/drivetrain is still breaking in. That's why I alternated my octane tests and did 6 tanks so I could do some averaging. I decided to do this testing because my 2008 Altima V6 clearly performs better and gets better mileage when run on premium (the requirement is for premium). That got me thinking....what if....??
To cut to the chase, the reason for the "big difference" is really very simple: the "change" made in the MO's fuel requirement in 2011 was in its marketing, not in its engineering. The VQ engine in the 2011 and 2012 MO is designed and tuned to run best on premium fuel. It has the knock sensors and electronic control unit (ECU) programming to advance/retard the timing based on pre-ignition ("knock" or "ping") detected by the ECU. It is the same engine that's put in the CrossCabriolet which still requires premium fuel. Because the "regular MO" starts at two price classes below the CrossCab, I suppose Nissan concluded that if a buyer is looking at a $45,000 + car, he/she probably doesn't care so much about the premium fuel requirement while buyers of a $32,000 to $36,000 car might.
I told the service manager of the Nissan dealer I use about my experiences with fuel grades, mileage, and performance at low engine speeds. I then asked about the change in fuel requirements in 2011. The manager told me that the MO engine was not changed in 2011, only its recommendation for fuel use was changed. He did admit that the dealers are told not to "advertise" this fact, but can say, when asked, that premium fuel is "best in an Murano."
If you are technically minded, you might want to know that the reason premium gives better mileage is that in order to compensate for pre-ignition (knock) caused by lower octane gas, the ECU will dump more gasoline into the cylinders. You will also dump more case with your right foot without thinking about it (i.e., to compensate for the definite flat spot between 2000 and 3500rpm, you will instinctively press the pedal down further). While the specs for the extra engine power and torque gained by running premium vs. regular fuel only amount to 5 hp and 8 lb-ft respectively, it is the torque curve that matters the most in terms of "seat of the pants" results. In practical terms, if you are disappointed in your MO's response to throttle at low speeds (both road and engine), you will notice an immediate benefit from running premium fuel--the engine will seem to have as much as 20 lbs-ft of extra torque when running at low speeds on premium. That's the "cost" to engine performance of retarded timing.
As for the gas mileage difference, I "did the math" and found that even at 20 cents extra for premium fuel (i.e., the cost for 91 vs. the cost for the 85 octane), it takes only 1 mpg improvement to make up the difference in fuel costs. It's even more of a no-brainer when comparing 87 octane (mid-grade) to premium 91 (the price difference in my area is generally about 6 cents between mid-grade and premium). At the typical 6-to-10 cents difference, I wouldn't even care if I got better mileage running premium versus mid-grade simply because of the performance improvement. However, my testing showed me that running premium fuel improved my consistent mileage by at least 1.5 mpg and by as much as 2 mpg. So, it actually costs me less to run premium grade than regular fuel and I get the increased torque (performance) improvement as a bonus.
Here's some simple math to show my general test results:
Trip length = 100 miles. (Divide 100 by the mpg noted below to get the number of gallons used for the 100-mile trip).
Cost of trip @ 18 mpg with premium (91) gas @ $3.70 = $20.57
Cost of trip @ 17.4 mpg with mid-grade gas (87) @ $3.62 = $20.80
Cost of trip @ 16.2 mpg with regular gas (85) @ $3.50 = $21.60
Summary: it costs $1.03 less to run premium fuel for 100 miles. Oh, and did I mention that the car performs a lot better?
While I think these numbers speak for themselves, I'm going to spell out my conclusion--i.e., premium fuel is the best choice cost-wise for a car that is designed to use premium fuel. The engine in all model years of the MO is designed to use premium fuel. The bean counters at Nissan thought they might sell more cars during a recession if they dropped the premium fuel requirement from sales and specification (user manual) literature. But while I can understand that sales decision, it's probably based on the assumption that the average American car buyer can't do even simple math.
Oh, if anyone has anything nice to say, please do. I'd like to think that my investment in time to write this detailed report has value to someone.
Peace.:29:
I did a search on the forum, so I know that many folks have had concerns about the octane needs of the MO, especially after Nissan lowered the requirement from Premium "91" down to Regular "87". My summary of those postings is that you'll see some people who believe certain things and some people who know certain things. The believers, heaven bless them, believe. On the other hand, the knowers, well, they know. There is a big difference in fact, although the believers will say otherwise (i.e., "you're wrong--the MO will not benefit from high octane gas because my Toyota Camry doesn't and so that proves it"). The reason I have related this summation will become apparent in a moment.
But before I tell my story, I'd like to request: 1) if you don't care about or don't believe my test results, please don't flame me. 2) If you think that you know better than me (i.e., you think you "know how the MO engine is designed" so what I report "can't be true"), just accept that your world view is what it is and please don't flame me. 3) Please don't flame me.
OK. Here's my story. I have found that running 91 octane, the highest available in my area, versus running 85 or 87 octane (the regular and mid-grade choices) makes a big difference in my MO. I get better mileage with premium (1-2 mpg) and the increased off-the-line performance is, well, amazingly better. I tested this "theory" over 6 full tanks of gas (at least 18 gallons of regular, premium, and mid-grade, average miles per tank, 310). That's almost 2000 miles during the hot time of the year (A/C running all the time, average temperature 92 degrees, relative humidity range 30 to 45%, altitude about 4500 ft). Fuel purchased at the same station at the same pump at the same time of day. No mixing of grades; at least 18 gallons of fresh gas per tank. Tire pressures checked at each tank fill. No extra cargo kept in car. Driver alone 75% of the time for each tank, with one passenger about 25% of the time.
Yes...I kept careful records. And here's some "fine print" for anyone who's really technically minded: miles at start of test = 3570; miles at end of test = 5550. Yes, I know, my engine/drivetrain is still breaking in. That's why I alternated my octane tests and did 6 tanks so I could do some averaging. I decided to do this testing because my 2008 Altima V6 clearly performs better and gets better mileage when run on premium (the requirement is for premium). That got me thinking....what if....??
To cut to the chase, the reason for the "big difference" is really very simple: the "change" made in the MO's fuel requirement in 2011 was in its marketing, not in its engineering. The VQ engine in the 2011 and 2012 MO is designed and tuned to run best on premium fuel. It has the knock sensors and electronic control unit (ECU) programming to advance/retard the timing based on pre-ignition ("knock" or "ping") detected by the ECU. It is the same engine that's put in the CrossCabriolet which still requires premium fuel. Because the "regular MO" starts at two price classes below the CrossCab, I suppose Nissan concluded that if a buyer is looking at a $45,000 + car, he/she probably doesn't care so much about the premium fuel requirement while buyers of a $32,000 to $36,000 car might.
I told the service manager of the Nissan dealer I use about my experiences with fuel grades, mileage, and performance at low engine speeds. I then asked about the change in fuel requirements in 2011. The manager told me that the MO engine was not changed in 2011, only its recommendation for fuel use was changed. He did admit that the dealers are told not to "advertise" this fact, but can say, when asked, that premium fuel is "best in an Murano."
If you are technically minded, you might want to know that the reason premium gives better mileage is that in order to compensate for pre-ignition (knock) caused by lower octane gas, the ECU will dump more gasoline into the cylinders. You will also dump more case with your right foot without thinking about it (i.e., to compensate for the definite flat spot between 2000 and 3500rpm, you will instinctively press the pedal down further). While the specs for the extra engine power and torque gained by running premium vs. regular fuel only amount to 5 hp and 8 lb-ft respectively, it is the torque curve that matters the most in terms of "seat of the pants" results. In practical terms, if you are disappointed in your MO's response to throttle at low speeds (both road and engine), you will notice an immediate benefit from running premium fuel--the engine will seem to have as much as 20 lbs-ft of extra torque when running at low speeds on premium. That's the "cost" to engine performance of retarded timing.
As for the gas mileage difference, I "did the math" and found that even at 20 cents extra for premium fuel (i.e., the cost for 91 vs. the cost for the 85 octane), it takes only 1 mpg improvement to make up the difference in fuel costs. It's even more of a no-brainer when comparing 87 octane (mid-grade) to premium 91 (the price difference in my area is generally about 6 cents between mid-grade and premium). At the typical 6-to-10 cents difference, I wouldn't even care if I got better mileage running premium versus mid-grade simply because of the performance improvement. However, my testing showed me that running premium fuel improved my consistent mileage by at least 1.5 mpg and by as much as 2 mpg. So, it actually costs me less to run premium grade than regular fuel and I get the increased torque (performance) improvement as a bonus.
Here's some simple math to show my general test results:
Trip length = 100 miles. (Divide 100 by the mpg noted below to get the number of gallons used for the 100-mile trip).
Cost of trip @ 18 mpg with premium (91) gas @ $3.70 = $20.57
Cost of trip @ 17.4 mpg with mid-grade gas (87) @ $3.62 = $20.80
Cost of trip @ 16.2 mpg with regular gas (85) @ $3.50 = $21.60
Summary: it costs $1.03 less to run premium fuel for 100 miles. Oh, and did I mention that the car performs a lot better?
While I think these numbers speak for themselves, I'm going to spell out my conclusion--i.e., premium fuel is the best choice cost-wise for a car that is designed to use premium fuel. The engine in all model years of the MO is designed to use premium fuel. The bean counters at Nissan thought they might sell more cars during a recession if they dropped the premium fuel requirement from sales and specification (user manual) literature. But while I can understand that sales decision, it's probably based on the assumption that the average American car buyer can't do even simple math.
Oh, if anyone has anything nice to say, please do. I'd like to think that my investment in time to write this detailed report has value to someone.
Peace.:29:
