once again, you know you're overworking your knok sensor by switching back and forth right? It's okay to use and stick with one. Switching is bad, very bad. Either you want the Max power or not. Or you plan to replace sensors and maybe more down the road with the pennies saved with occasional 87 use.



I think the main point behind these new regulations should be: Clarify that the HP #s are engine power or real world wheel power.

Yeah my VQ puts our 265 sitting still, but what can I flex while actually drivnig the whole car and not sitting on a Dyno?

 

Just curious, How do you overwork a knock sensor? Isn't it going to be checking for knock at whatever interval the ECU requires? I'm new to this vehicle so maybe I'm missing something. When I picked up my car the rep told me to use 89 octane (though the manual say 87) fuel for 3 out of 4 tanks and make the 4th premium. I've never heard this engine knock. Of course he also told me to change the oil at 1200 and when I mentioned it to the Service Manager he told me it was un-necessary and to wait to til the 3750 mark. I also drive a RAM Hemi which they recommend run on 89 when towing and I've never heard it knock on 87 (though I never tow with 87).

 

I'm curious about this as well.

I don't know how it would wear out (although they do wear out....I had to replace on on a 96 Maxima) faster with regular than premium. Maybe there is some physical movement inside of the sensor that wears faster when the engine is pinging?

 

okay, maybe the sensor won't break, but the mere fact it needs to work to prevent knocking since knocking will occur from changing around. Mess with your octane and you car works harder to adjust the detonation timing. You keep switching, you will experiecne knock which I thought was undesireable.

I suppose if you mix 3/4 with 89 then top it with 93, you'll make your own 90 (actually equals that). Then your sensor will run your engine accordingly. Or going with 87 with a bit of 93 = 88.5 you should just use 89. That seems way too inconvient and pointless to me to stop one and pump another.

So say you run 3 tankfuls of 87 and one of 93 on the 4th tank.... your car is adjusted to dentonate according to an Anti-Knock Index of 87 for 3 tanks. Then you throw 93 in. It works to adjust and as soon as it gets ready, here comes 3 more 87 tanks. You're risking pinging and kncocking when you're average is 89 anyway.

So Why Not Just Always Use 89?????

Now I have to split this thread apart and move it to Fluids and Lubricants

Please continue on with HP.

 

NismoMax80 is telling the truth.

In the good old days, it was common to throw in a tank of 'hi-test' or 'ethyl' every so often. Those days are gone.

The onboard computer of the 6th gen Maxima uses an octane sensor to determine the exact octane, and it very gradually adjusts according to the octane found.

But it takes several tankfuls of gas to make the complete adjustment for a different octane. Those switching octane as often as every fourth fill-up will never have their engine using fuel in the most efficient manner.

But it is your engine and your wallet. Whatever makes you happy.

 

I can't remember ever disagreeing with lightonthehill before. On his point made above on an octane sensor, I must disagree.

Because I was not certain about there being an octane sensor in vehicles, I consulted with a true expert on engine design. Besides citing the quote above, I also said to him: "I thought it was the knock sensor that did the adjusting. This person says the sensor in the fuel tank or fuel line actually tests octane. I find that hard to believe given the difficulty that all oil companies have testing octane without using an octane test engine."

Here is his reply to my querry: "Typically gas engine systems rely on knock sensors on the engine. A few companies have added ionization probes to the spark plugs for misfire detection as well. That is pretty much the limit of the technology in gas engine design today. I'll check around but normally a direct fuel measurement is made in the fuel line using an optical measurement and is done for flex fuel vehicles. It does not make a lot of sense to have a tank based sensor as the engine cares what is in the line now not what may be in the line later. Not to say that it does not exist, it just does not make as much sense."

Based on this, I think "light" should advise us how he knows about an "octane sensor" on the 6 Gen Max.

 

Oh by the way Nismomax80, I find that you have a really good sense of humour and I'm with you all the way pal!

 

I actually design automotive ECU's so I have a little knowledge about this. The knock sensors I've worked with are basically special microphones that feed a modulated audio signal into the ECU. The ecu will adjust the engine timing and fuel mixture to eliminate the knock. The only way I could see someone wearing out their knock sensor would be if the the engine continued to knock because the ecu could not for some reason adjust the engine timing to eliminate the knocking...for example... really low octane gas or something was faulty with the ecu itself.

 

okay, we're beyond the knock sensor, is it bad for any part of the car to keep switching octanes forcing it to constantly readjust?

 

My earlier posts on this thread were moved, so I no longer seem to get a notice about a new post. Hope this one will correct that.

Blue04SE describes how I understand the knock sensors work in our Max's. It was designed to be checking for detected knock and adjusting the spark advance to just eliminate any knock. That way it should give you as much spark advance as the engine can handle without knocking.

Where I live the elevation is 6,000 feet above sea level and my house is above town at 7,200 feet. I burn 85 octane regular in my Max. But that octane at 6 K feet (for non-turbocharded engines) is equivalent to about 91 octane at sea level. When I drive east the elevation slowly declines and the knock sensor adjusts the spark accordingly to handle the 85 octane that is still in my tank. I fill up in western Nebraska with 87 and now the mixture in the tank is about 86.5 octane. The knock sensor continues to check for knocks as the elevation continues to decline and the octane in the tank gets closer to 87.

Why did I go to all of this detail. Because this is the way the car was designed to handle different operating conditions and different octanes being burned. You don't want to try and burn 85 octane in a Max at sea level, but short of that, 87 should work fine at sea level. I do it every time I go east.

I guess some members will worry about having the spark advance system work too hard and wear out. My worry is that if it does not work doing what it was designed to do, it will freeze up and not work when it is needed to protect the engine from engine knock.

 

How about u pay the extra $3 bucks at the pump and keep your car happy

 

My car is happy that I own it and care for it and garage it every night (when I'm home). It works well for me and I take good care of her.

I can't help if some on this site don't understand the basic technology of the internal combustion engine (that's a gasoline engine for those who -- No I can't say it here -- no flames). American English is what I speak and write. Sorry you can't understand some simple technical terms.

 

I agree with you on most things, SilverMax 04, but I do disagree with running 87 octane gasoline in an 04 Maxima at lower elevations. I am sure it adversely affects the performance and fuel economy of the 3.5 litre engine you paid so much for. Why don't you conduct an experiment and buy some 91 or higher the next time you are on an extended trip below 5,000 feet. Fill up when the 85 octane gasoline is virtually depleted and report back to us.

I wouldn't dream of running 87 octane in by 95 Maxima, but I am at sea level.

 

Silver max your trippin off nothing, go take your $3 and buy another octane book and make yourself feel better. I know more than simple english and i do understand what your talking about, i was just having a little fun. No reason to be rude , besides if Nissan engineers make some of the best engines in the world and they tell you to put a certain type of fuel in the car dont you think they know just a little better than you? I know they dont get it all right but im pretty certain the octain level they say to use must be correct i mean its not easy telling a consumer buying a car to dish out more money for gas compared to other cars in its class, There must be a reason. So feed your car what you want its your investment but the next time you talk to me you need to learn how to distinguish a friendly joke vs. criticism .

 

1) And I was having a little fun with you -- you seemed to miss that, too. I wanted to make it seem like I wanted to "flame you" without ever doing it. Guess I should give up on trying to be a comic.

2) I do follow what the Nissan engineers say about octane for the 6th Gen Max that I drive. They tell me for maximum performance, I should use premium. I take that to be racing, hot-rodding, dyno testing, hill-climbing, etc. They also tell me that the car will perform quite well (but not at the maximum) burning 87 octane regular.

Since I don't push my Max to the max very often -- can't remember when I did so, ever -- I follow their advice and burn regular. The Max performs fine for me and I save some money on the high cost of gasoline.

 

I wanted to get the exact Nissan quote on gasoline for the 2005 Max. I could not locate it on this site, so went to the source:

http://www.nissanusa.com/vehicles/ModelSpecifications/0,,124646||,00.html

In the first footnote on the engine: "3.5-liter DOHC 24-valve V6 engine: 1 Use regular unleaded fuel with 87 octane. For maximum power, use premium fuel." Can't be any simpler than that.

It is also of interest that footnote # 2 "SAE Net. Horsepower will test lower under revised SAE testing procedures. Engine performance will not change."

 

Funny you should ask. I did just what you requested on my last trip to the East Coast this past July driving the back roads of Colorado & Kansas to I 70, then I 70 to St Louis, I 64 & I 57 & I 24 to Nashville, I 40 to Ashville, NC, and I 26 to Columbia, SC and the beach. I returned via Knoxville, Cincy, Chicago, Green Bay, Minneapolis, Des Moins, etc.

My cruising style is to try and drive 8 to 9 mph over the speed limit using cruise control, but not faster than 79 mph. So on the back roads I was doing 74, I 70 doing 79 in KA and 74 in MO, and so on. I know that there needs to be more than one tank of premium to even begin to show any results. Here they are, in detail, with the MPH number being what the computer said my average speed was for each leg of the trip. (When MPH goes down below the 50s, you know that there was some city driving in that tank of gasoline.) You need to remember that the MPG (that I calculate) and the Cptr (Computer) MPG applies to the average fuel in the tank based on redidual fuel plus the new fuel from the previous fill. Over time since I bought my Max in May of 03, I've come to believe that the computer calculation of mpg is probably a better calculation that my manual calculation -- given the variance each time when filling the fuel tank:

Departed home with a full tank of 85 octane regular on 7/6.
Loc _ Miles _ Gallons _ Oct _ MPG __ Cptr MPG __ MPH
KA _ 396.3 _ 15.009 _ 87 _ 26.40 ___ 24.1 ____ 69
MO _ 356.1 _ 14.445 _ 87 _ 24.65 ___ 25.9 ____ 69
KY _ 308.6 _ 11.529 _ 93 _ 26.77____ 26.5 ____ 64
TN _ 218.8 __ 7.596 _ 93 _ 28.80 ___ 27.4 ____ 65
SC _ 198.5 __ 5.524 _ 93 _ error ___ 27.9 ____ 58
SC _ 125.0 __ 5.505 _ 87 _ 22.71 ___ 27.2 ____ 43
SC _ 316.1 _ 13.368 _ 87 _ 23.65 ___ 25.5 ____ 30
SC _ 252.2 _ 11.769 _ 87 _ 21.43 __ missed __ missed
TN _ 165.6 __ 4.652 _ 87 _ error __ missed __ missed
KY _ 223.4 __ 9.189 _ 87 _ 24.31 __ 26.1* ___ 66*
IN _ 159.0 __ 6.224 _ 87 _ 25.55 __ 26.0 ____ 64
WI _ 346.7 _ 13.837_ 87 _ 25.06 __ 25.7 ____ 43
WI _ 156.3 __ 6.946 _ 89 _ 22.50 _ 25.6 ____ 42
MN _ Not full _ 8.854 _ 87 _ below _ 26.1 ____ 57
IA _ 552.3 __ 11.564 _ 89 _ 27.05 _ 24.9 ____ 69
NE _ 145.3 __ 6.638 _ 89 _ 21.89 _ 24.9 ____ 69
NE _ 250.9 _ 11.056 _ 87 _ 22.69 _ 25.0 ____ 73
CO _ 401.1 _ 14.870 _ 85 _ 26.97 _ 25.8 ____ 48

The two missed partial readings were when traveling caravan with another vehicle, and they did not give me time to collect all data. The two readings with a * below the missed readings are an average of all three segments. The prices were so high in MN that I elected not to fill up. I knew that IA prices would be better. In Wisconsin, the 89 was the same price as the 87, and in IA and eastern NE the 89 was cheaper than 87 due to the ethanol tax waiver in those states.

Not certain what this proves about better mileage with higher octane. Yes there was some of that, but there were also times when the lower octane did just as well. I believe there were too many other factors (high temps and head or tail winds) to accurately draw any conclusions.

On a second look at the numbers, it appears that 93 premium may get from 1 to 2 mpg more than 87. That is definitely worth something. Is it worth an extra 20 cents per gallon? I did a what-if calculation using comparable prices in the midwest (2.50 for 87 and 2.70 for 93) and assumed that the premium would get an extra 2 mpg over the 87 which would get 25 mpg. Turns out the cost per mile for gasoline is the same (in this case) at 10 cents per mile. Given that an extra 2 mpg seems to be the best that premium can deliver (and on average it might be less), I will stick to regular. But premium could make more sense if the price difference is less than 20 cents. And mid-grade at the same or lower prices also makes sense.

I do agree that 87 will reduce track times and top HP at the dyno. If racing use premium, otherwise use 87 and possibly save $.

 

What about passing acceleration on some of those back roads? How does 87 octane stack up relative to 93, SilverMax?

You also scarcely even gave the 93 octane a chance. Your initial fill of 93 appeared to be when you had quite a bit of 87 octane left in the tank. By the time of your second fill of 93 you had barely run out the mix of 87 and 93 you were running. Your last fill of 93 was run a whopping 125 miles and you only ran 93 for a total of 542.3 miles. I can get than many miles out of a full tank of gas on a highway trip, albeit down to fumes. By your own admission it may take a few tanks of premium to show results.

Then you switched back to 87 octane for 7 fills at lower elevations. Why did you do that?

You didn't even give the premium a fighting chance in your trial and shouldn't have even wasted your time conducting it. Had you filled with premium every time, other than your initial fill and last fill when you got home, and assuming the 2 mpg incremental mileage assumption on premium is valid, do you not realize that the entire cost differential for about 4,000 miles (of the 4,800 mile total) would have been in the order of $2 more?

Obviously you are not a Maxima enthusiast and may be better served with a cheaper, more practical vehicle for your driving enjoyment and put some cash in your pocket, given you run low octane gasoline on a road trip with a car having a 10.3 to 1 compression ratio.

 

Point taken we are all good, and your gas readings sound very interesting. But have you ever thought about making that kind of a trip again using 93 octain?

 

That is what I was getting at.

 

For what its worth, I just made a run from Cincy to Toledo and back yesterday for a meeting. I decided to check the highway mileage just to see what I got. These numbers are what the computer calculated. These are pretty much all Highway miles, maybe a total on 10 city miles on each leg.

Cincy to Toledo 208 miles no A/C 30.4 mpg
Toledo to Cincy 212 miles A/C 30.0 mpg

This was with BP 89 octane

 

You all make good points. To properly do any test like this you need two identical cars running the same trip at the same time. Not feasable. So I do the next best thing and run premium for part of the trip. Correct, I did not run premium long enough for a good test.

I'll be driving to Chicago in December and will try a slightly different test: I will drive out using 85, 87 and 89 octanes -- the cheapest gas at each station on the way. (I try not to buy gasoline in Chicago due to their high prices there). On the trip back, I will fill up an almost empty tank in Eastern Iowa with 93 octane and buy 93 octane at the other stations on the trip home. This should give a better test of premium's performance, yielding better results; and becaue the trip is over the same road each way, more comparable.

Some Questions Answered:
"What about passing acceleration on some of those back roads? How does 87 octane stack up relative to 93, SilverMax?" I only drove back roads in CO, Western KA and SC. There is so little traffic on the roads in the west, there was no reason to push the car when passing the few times that I did pass. When driving in SC it was caravan style with the wife saying not to pass because the 2 mini-vans following could not pass as well. So don't have much to report here. When I do pass in SC using 87, the car certainly seems to have a lot of pep, but I'm certain she would have more with premium in the tank.

"Then you switched back to 87 octane for 7 fills at lower elevations. Why did you do that?" Because I'm cheap. I also did not think that premium would be worth the extra money. It now looks like a better test is needed to determine that point.

"Obviously you are not a Maxima enthusiast and may be better served with a cheaper, more practical vehicle for your driving enjoyment and put some cash in your pocket," You are possibly correct. I first considered a Honda Accord when I bought my Max. But I needed two things and Honda did not offer them both in one vehicle and Max did: 4 door sedan and a manual transmission. Now that I have the Max, I've come to really appreciate both the VQ and the 6-speed. Guess I now have to decide if Premium gasoline is a part of that equation.

I know that here in Colorado I can get 91 octane performance with 85 octane. The question when I drive east is: 1) do I go for 87 and 89 octane (depending on the price of each), or 2) do I pay the extra for 91 or 93 octane premium. I hope my December test will give me the answer to that question.

 

That's pretty good mileage assuming the computer is accurate. It would be interesting to determine the actual mpg the old-fashioned way.

 

Wow I must have a defect. I don't get any where near that MPG.

 

On a few occasions I've gotten 30 mpg on the open road. But I think I had a slight tail wind and the temps were in the 30s or low 40s. I tend to get more like 26 to 29 mpg most of the time. And about 20 to 24 around town.

 

Hopefully your results in December are not skewed by a tailwind going east, which is likely, and a head wind returning home, SilverMax 04. I would be inclined to run 93 both ways, but the results could be affected relative to your recent trip by the use of winter gas.

 

Good points. But I've also seen winds that time of year from the south, the north and the east. In the summer the prevailing wind tends to be from the west. Less so in the winter.

I'll try to determine wind direction in December (not many flags on the route) and record that info as well.

Bottom line: I don't think that the higher cost of premium will make up for it by better mileage. But I certainly want to find out for certain. I have a bias, but I also want to be certain it is correct. In my mind it would be great if the higher cost of premium more than paid for itself in better mileage. Then I could get both better mileage and slightly better performance by using premium. I hope this test does all of that for me.

Finally: Winter gasoline has more butane blended in it, thus it has somewhat less energy per gallon. But my best mileage in my Max has been in the winter. Must be that a warm Max VQ engine and cold outside air work to provide the best mileage -- even with winter gasoline.

 

My best mileage has always been in the summer as my Maxima has never seen an extended highway trip in the winter for comparison purposes. I don't even like driving it in the rain and I live on the "Wet Coast"! Plus we have winter gas, which I believe, drops my fuel economy by about 10%, although the colder startups could account for some of that 10%.

 

Don't like driving in the rain in BC! Is that like a duck not liking water? (I would rather not drive in the rain either after hydroplaning at 75 mph -- the speed limit -- and totaling my previous car.)

If the cold start is too much a part (like 10%) of your trip, it's hard to get a good mileage reading. I'm lucky that my Max can live in a garage that never gets below about 35 degrees F. When I visit Chicago in the winter, the Max has to work. Last year it got to 20 below zero F the morning we left to come home. Was that ever uncomfortable.

 

I'm staying with the high octane despite the prices want my baby drinking the best juice.