My trip computer usually tells me I'm getting 22 mpg if I'm being good. Lately it's about 20! Is anyone else getting such poor mileage? Could it be an incorrect computation? I spend crazy dough on gas, and I'd really like to know what's going on.

 

How many miles do you have on your Max? If you've barely started racking miles, give it some more time until the engine breaks in. I didn't start getting good mileage on my 2k2 until past 10k.

Also, on the trip comp. If it's anything like previous gens - it will be off by 2-3mpg.

 

Think overall I am averaging 23-24 mpg and I live in a city so that is good for me. I do pay attention to it rather carefully and when I travel on longer trips with mostly highway driving, and I usually get an average of 28-30. Now granted this is what the computer is telling me, could be a farce but I have yet to test it the "old school" way.

 

I'm getting about 24 on my SL with mostly city driving. I have seen as high as 30 on the computer while I was teaching my daughter how to drive... in the country at at around 45 mph.

My computer is actually on the pessimistic side, whereas when I compute it by taking miles divided by gallons, I get about 1.5 mpg better.

I'm getting better mileage with my 04 than I did with my 00 GLE.

 

I'm averaging about 20 MPG, but that is in miserable Atlanta traffic most of the time.

 

I am averaging 22-23 and my computer seems to be almost dead on. I get ****ty mileage on trips too, but I think that has to do with me going 90 for hours on end

 

While I was driving through california in august averaging 85+ mph I was getting more then 29 miles a gallon. But I'm averaging about 22-23 mpg in town.

 

No way, I think you had a serious miscalculation on that one.

 

I was suprised myself. Not only did the computer in the car come to that, my calculations got those numbers too. But remember this was through the flat straight parts of california. I was getting about 500 miles per tank. I got it both directions. (north and south, about 2 and a half weeks apart) Around here with some small hills I can average 28. Infact, my trip from here to Seattle, I averaged 27.7, and that is going over a pass averaging around 70 mph. I have 4600 miles on my car, now. I just had 700 on my car when I left for california, and about 3500 when I got back.

 

I avg. 19mpg in the city with 11,000 miles on a SE.

 

Have you thought that your milage may go down if you get it on it alot at the light or whenever?

its a pretty powerful engine that can suck up the gas pretty fast, depending on how slow and safe you drive, thats how your gonna get your best MPG out of that car.

 

I know that is why my MPG sucks so bad, but I bought the car for the fun, not for the mileage... if I wanted good gas mileage, I would have kept my V10 Excursion

 

I've posted on earlier G-6 threads about both MPG and gasoline octane requirements for the G-6 Maxima. If you're interested in what I said earlier, go to this thread. My comments are Posts # 26 and # 30:
http://forums.maxima.org/showthread....0&page=1&pp=30

My earlier comments were made when I was still incorrectly informed (by a dealer tech) that the compression ratio on the VG 3.5 engine in the new Maxima was 10.0:1. I now know that the correct compression ratio is actually 10.3:1. Not much difference, but definitely higher than other cars (like the Honda Accord with a 10.0:1) that recommend burning regular gasoline. Also, a good friend (who's an engine tech expert) suggests that while the Maxima owners manual says the new Maxima can safely burn 87 octane regular gasoline, with a 10.3:1 compression ratio I'm pushing the limits of this engine ability to properly burn regular gasoline. Because of this new information, I'm now recommending burning "mid-grade" gasoline when operating the Maxima at lower elevations.

You are probably asking why I'm bringing elevation into this discussion. Turns out it’s a well-researched fact that an engine's octane requirement decreases with increased elevation. (This octane decrease does not apply to turbo-charged engines.) The reason octane requirements decrease with increased elevation is the reduction of air pressure inside of the engine's cylinder where the fuel is burned. The thing that is hard to accurately determine is exactly how much the octane requirement decreases with each 1,000-foot increase in elevation. I can cite technical papers that list this decrease per thousand feet at between 0.5 and 1.5 octane units. This fairly wide difference is due to differences in each individual engine being tested. Knowledgeable tech experts generally assume that the mid-point of 1 octane unit per thousand feet in elevation is about right for most gasoline engines.

I will use this assumption plus my plan to use mid-grade gasoline at lower elevations to determine what gasoline octane to burn. Thus, if my Maxima needs 89 octane at sea level, it should provide similar performance from 83 octane gasoline at 6,000 feet elevation -- where I do most of my driving. The lowest octane I can buy in Colorado is 85 octane -- which I've been doing with very satisfactory results.

(Interesting fact: gasoline test engines produce about 18% less power at 5,200 feet elevation -- Denver -- than they do at about 400 feet -- Detroit. This loss of power due to higher elevation can’t be recovered by increasing gasoline octane. Turbo-Charging is the only solution for this problem.)

As a matter of "full disclosure" I should point out that I had no difficulty burning 87 octane regular gasoline in my new Maxima (when I still thought the compression ratio was only 10.0:1) at sea level in South Carolina this summer. My Maxima stopped burning oil (about 1 qt per 2,000 miles) when the car had gone about 4,000 miles. I'll not report any mileage numbers before this happened.

With this background, what kind of gasoline mileage have I been getting in my new Maxima (7,800 miles on her now) with a 6-speed transmission? Below, I’ve grouped similar driving experiences together. I've also kept records of what the Maxima's computer said the MPG was and what I calculate the MPG based on the gallons to fill my tank.

I got the best mileage at sustained freeway speeds (no stop and go driving and few quick starts). Stretches of freeway driving are grouped together:

MILES ___ COMPUTER ___ CALCULATED ____ Avg MPH
170 _____ 27.9 mpg _____ 31.7 mpg _______ 65 MPH
364 _____ 28.7 mpg _____ 27.2 mpg _______ 70 MPH
534 total _ 28.4 mpg _____ 28.5 mpg _______ 68.4 MPH

315 _____ 27.2 mpg _____ 26.2 mpg _______ 65 MPH
147 _____ 26.9 mpg _____ 32.6 mpg _______ 66 MPH
256 _____ 26.0 mpg _____ 23.5 mpg _______ 70 MPH
84 ______ 26.1 mpg _____ 32.9 mpg _______ 73 MPH
234 _____ 26.9 mpg _____ 27.3 mpg _______ 66 MPH
1,036 total 26.7 mpg ____ 26.9 mpg _______ 67.25 MPH

The average at the bottom of each group shows that over a longer distance (where gas tank filling differences don’t matter as much) the mileage reading is almost the same coming from the Maxima’s computer and what I have calculated from gasoline consumption.

How about mileage from “around town” (again grouped):

MILES ___ COMPUTER ___ CALCULATED ____ Avg MPH
122 _____ 21.9 mpg _____ 24.6 mpg _______ 25 MPH

299 _____ 25.4 mpg _____ 23.5 mpg _______ 22 MPH
221 _____ 22.4 mpg _____ 20.0 mpg _______ 22 MPH
289 _____ 26.9 mpg _____ 33.4 mpg _______ 31 MPH
809 total _ 25.0 mpg _____ 24.9 mpg _______ 25.2 MPG

I’m actually pretty impressed with how well the Maxima computer seems to get the gasoline mileage calculations. At first I tended not to believe its readings, but now I’m more inclined to believe it is more accurate than my calculated numbers for each individual segment.

 

I Have Been Averaging 22.2 City Mpg And 31.8 Highway Mpg
Total Combined Average 25.9mpg

Sunco 94 -octane +0 To 60 Boost Octane By Prestone And Chevron Fuel System Cleaner

When The Red Light Turns For Gas Empty
I Fill Up The Car And It Takes Only 15 .4 Gallons Gas And Miles Are 400-420 Each Time Per Fill Up
2004 Sl Maxima

 

Here we go with the octane again. On that other thread, I clearly pointed out, with references to an experts quotes about what higher octane does for your car, and what it doesn't do.

In summary, if your car is not pinging, then you don't need a higher octane. If your car drives fine with 87 octane (no ping) then it is burning at the optimal temperature. If it pings, then you need to step up to a higher octane in order to have it ignite at the optimal point. What the higher octane will not do for you, is change your mileage or your performance. It clearly stated that if you use an octane that is too low (it pings) then you will suffer a performance loss, but if you use one higher than what you need, it will not result in a performace gain.

 

You "could" actually lose mileage by using too high of an octane rating in a vehicle requiring 87.

 

correct.

remember you guys don't drive 1973 buicks. the ECU will know when to retard the timing.

 

A LOT of things "COULD" happen

 

Quote:
Originally Posted by gmc74
"Here we go with the octane again. . . .

"In summary, if your car is not pinging, then you don't need a higher octane. If your car drives fine with 87 octane (no ping) then it is burning at the optimal temperature. If it pings, then you need to step up to a higher octane in order to have it ignite at the optimal point. What the higher octane will not do for you, is change your mileage"

{This far in your quote I completely agree with all you have said.}

"or your performance."

{Here's where I don't completely agree with what you said. If you use lower octane gasoline, the ECU will detect this octane and retard the engine's spark timing. If you are pushing the engine at the track or on the strip, you will lose the ability of the VQ 35 engine to perform at the maximum this engine is capable of producing. Driving on the street or highway where you are not pushing the engine, you will likely notice no performance difference due to higher octane -- which is what I think you were trying to say.}

"It clearly stated that if you use an octane that is too low (it pings) then you will suffer a performance loss, but if you use one higher than what you need, it will not result in a performace gain.”

Also, DanNY has it correct when he said: "remember you guys don't drive 1973 buicks. the ECU will know when to retard the timing."

So why have I decided to use mid-grade (89 octane) gasoline in my Maxima when driving below about 2,000 feet in elevation? Three reasons:
1) I don't want to trust my hearing that there is light engine knock, particularly at highway speeds. I will feel safer using mid-grade.
2) As a car "ages," deposits in the engine typically increase the octane requirement for that engine. Gasoline additives help keep this under control, but not completely.
3) At some point the spark may be retarded by the ECU too far. I would rather not push that point, and mid-grade should provide the margin.

These three reasons are ranked in importance. Most important: Light, short-duration engine knock is not a problem. However longer-term light engine knock will damage your engine. I'm buying insurance when I use mid grade gasoline at lower elevations. I believe that all three of these reasons were why “a good friend (who's an engine tech expert) suggests that while the Maxima owners manual says the new Maxima can safely burn 87 octane regular gasoline, with a 10.3:1 compression ratio I'm pushing the limits of this engine’s ability to properly burn regular gasoline.”

 

You 6th genners have more HP than us 5th genners, but our manual says to use nothing less than 91 octane, whilst yours states 87. Sounds like Nissan is fudging numbers to me in the hopes that the lower octane usage number will draw in more people to purchase the car (much like the hotly debated 255 HP 5th Gens--it was originally labeled 260 to better compare with the TL-S...). Since Honda's 3.0 240 HP V6 uses 87 octane, Nissan's does too, regardless of whether or not it is the best thing for the engine.

 

The owners manual says that premium is the "BEST" for this engine. But it also says you can burn 87 octane (or even 85 octane above 4,000 feet elevation). You have to read the manual carefully to find this statement. Everywhere else, all you see is "burn premium gasoline."

Also note that the Honda 3.0 L engine has a 10.0:1 compression ratio and the VQ35 in the 6-Gen Maxima has a 10.3:1. This is why I now believe that mid-grade (below about 2,000 feet elevation) is best for this engine.

 

I think everyone needs to go out and read up on what the different octane gasses do.

Here is reality, if you put gas in your car, no matter how low the octane, and it doesn't ping or knock, then it is fine. There is absolutely no benefit to using a higher octane. It doesn't prevent deposits any more than an 87 octane gas, nor does it raise your performance or mileage.

Your cars computer is going to adjust the timing so your cylinder sparks at the right moment to get the optimal ignition of the gas in the cylinder. If the octane is too low, and the gas fires too quickly, then you get a knock, and you need to raise the octane level.

Here is a great website that I think everyone should read before they continue to post in this thread, you will be a better person for it

http://www.handymanusa.com/articles/octane.html

 

If you don't like that article, try one of these-

http://www.cyber-north.com/autotipnet/octane.html

Many drivers still believe that the higher the octane rating of the gasoline, the greater the power and the better the performance their vehicle will have. This isn't true. If your engine runs without knocking or pinging on regular fuel, then you will have exactly the same power on premium fuel.

http://www.cucarzone.com/PremiumGas.htm

There are probably 100 more if you look for them.

 

Your statement was true before modern engine technology allowed high compression engines (like the VQ 35) to burn regular gasoline by adjusting the engine to handle the lower octane gasoline. See my comments around statements from two of the sites you recommended.

I did go to your first suggested site. There is nothing in this site that disagrees with what I’ve said in my earlier posts. Below I’ve copied the important points about octane from this site. {I’ve added my comments in these brackets.}

~~~~~~~~~~~~
In fact, in most cases, using a higher octane gasoline than your owner’s manual recommends offers absolutely no benefit. It won’t make your car perform better, go faster, get better mileage or run cleaner. Your best bet: listen to your owner’s manual. {The 2004 Maxima Owners manual recommends Premium Gasoline. It also says that Regular gasoline will work, but they still “Recommend” Premium.}

The only time you might need to switch to a higher octane level is if your car engine knocks when you use the recommended fuel. This happens to a small percentage of cars. If it was designed for regular gas, but knocks, often that means you need a tune up. {My earlier point was that I didn’t want to depend on my ears to detect persistent engine knock (particularly at highway speeds) given the loud music they’ve heard for years. I consider Mid-Grade gasoline an insurance policy against undetected high-speed engine knock.} . . . .

Listen to your car’s engine. If it doesn’t knock when you use the recommended octane, you’re using the right grade of gasoline. Knock occurs when cylinder pressures are high. It is normal for an engine to ping a little at full throttle because cylinder pressures are very high at full throttle. Engine knock, however, should not be ignored since it can result in serious damage to the engine. High octane gasoline burns slower than low octane gasoline. The slow burn prevents engine knock when cylinder pressures are high.

If your engine runs well and does not knock or ping on low octane gasoline, there is no advantage in switching to higher octane gasoline.

A few car engines may knock or ping - even if you use the recommended octane. If this happens, try switching to the next higher octane grade. In many cases, switching to the mid-grade or premium-grade gasoline will eliminate the knock. If the knocking or pinging continues after one or two fill-ups, you may need a tune-up or some other repair. After that work is done, go back to the lowest octane grade at which your engine runs without knocking. . . . .

{One final point, that I don’t think the above advice disputes: The VQ 35 engine was designed to burn Premium. All tests of full-throttle torque and HP were done burning Premium. If you plan to race your Maxima, burn Premium when you do.}

~~~~~~~~~~~~~~~~~
GMC74 also suggested another site that says:

But as a car gets older, depending on how the car has been driven and cared for, it may need a higher-octane gasoline anytime between four and six years. That's because carbon deposits inside the cylinders raise the combustion ratio, which in turn raises the engine's octane rating. You may notice that your car operated fine on regular fuel when it was new, but pings on regular as it gets older. So, the higher-octane fuel is not something to pamper a new car with but rather help keep an older car running properly. In addition, premium gasoline has some other selling points. Most premium gasolines have a higher-quality additive package put in at the refinery. The actual additives in a particular brand of gasoline are generally not disclosed by refiners. But usually they include detergents and other solvents that keep the carburetor and rest of the fuel system clean.

{Yes, this is essentially what I said in my earlier post when I talked about deposits increasing octane requirements. Also, at one time refiners (I worked for one that did) put a stronger additive package in Premium. I suspect that may still be true today, but no longer have direct knowledge. Rather than burning Premium for the possible better additive package, it’s smarter to put an additive supplement such as Chevron Techron in your gas tank every 10,000 miles or so.}

 

what did we learn today kids?

use whatever gas YOU want to use.
use whatever gas YOU want to pay for.

guys...both sides have their points.

gmc...what you state about the power gains i believe was true of older cars...IE 3rd gens and 2nd gens...and others.
but i believe with cleaner and leaner running cars that puts out more power the ECU will take advantage of the higher octane fuel that you put in to the tank. even in my 2000 camry V6..it states it runs on regular..but for "improved performance" (direct quote ) to use premium.

i'm sure the improve performance is more **** dyno than anything else..but it probably contributes more to the fact that it will ping less and give u a more even power across to board.

if you guys want to buy premium buy premium if you want to buy mid grade...buy midgrade. if you want to buy regular buy regular.

(also i'm watching this thread....NO FLAMES!)

 

True DanNY, and folks remember this, the new AV6 gains 10 HP/TQ by using premium fuel over the standard 87...

 

FLAME!



I just find it so funny that there is such a misunderstanding about higher octane levels, as if it was a special turbo or something

 

Just so you know, that first statement wasn't mine, it was taken directly from that website.

I don't know why Nissan advertises that it runs best on Premium, but that it will run fine on Regular. If I had to guess, I would guess that it sounds like more of a high performance car when it requires premium and that is what they are going for.

 

i know what you're saying..it's just a lot of marketing brain washing the public.

 

Don't go by the computer, as it only shows an estimate. When you get gas, calculate it yourself.

 

Surprisingly, my computer has been almost 100% accurate. It has been of small amounts on a few occasions, but not more than a few tenths, almost always less than a gallon off. I was more surprised than anyone, this is the 3rd or 4th car that I have had with an on board computer that calcs mpg, and the only one that was close to accurate.

 

DanNY understands how Modern Engine Technology works -- whether it's in a Maxima engine, a Honda engine, or a Toyota engine. He said it in his qoute above, but it bears repeating: "with cleaner and leaner running cars that put out more power, the ECU will take advantage of the higher octane fuel that you put in to the tank. even in my 2000 camry V6..it states it runs on regular..but for "improved performance" use premium."

GMC says that: "I just find it so funny that there is such a misunderstanding about higher octane levels." Although tempting, I won't FLAME, as DanNY made my point in his important qoute, above.

And I certainly agree with DanNY's quote: "if you guys want to buy premium buy premium if you want to buy mid grade...buy midgrade. if you want to buy regular buy regular." That is exactly what I'm doing. I buy regular when I feel certain that it will not result in high-speed light engine knock. I buy mid-grade (89 octane) when I operate my Maxima below about 2000 feet elevation to be certain I don't experience high-speed engine knock. (This is more of an "insurance policy" against light high-speed engine knock than for added performance, as I certainly can tell no difference between 87 and 89 octane in street or highway driving.) If I were to take my Maxima to the track, I would buy Premium to get the absolute most out of the engine.

 

gmc74, i'm curious now... the Z was dyno'd using 93 and 110 octane gas. It showed to have an increase in HP and TQ with the 110.

Also, the new generation Accord (V6) has also shown to produce more power going from regular gas to premium.

I may have missed a point or two from all the recent posts, but i'm curious to know your stand on this.

(p.s. this is not a flame/hate/whateveryoucallit post)