SilverMax_04

That's all I ever really recommended. Try it. It won't kill your Max's VQ engine, and you can decide, like dr-rjp did, what works best for you.

The one thing about what rjp reports that is surprising is the difference in auto trannie down-shifts: "downshifting from 1st to 2nd produces more hesitation, shudder or "shift shock" than before." Since I have a 6-speed, I do not get these problems. But I really doubt if the difference in gasoline octane is causing what he is experiencing. No way to prove it, but I am doubtful.

I have noticed that a number of gas stations in my area no longer have prices where regular is 10 cents cheaper than mid-grade and premium is 10 cents more than mid-grade. The regular is becoming more of a "fighting grade" and is 14 cents cheaper than mid-grade, while premium is only 10 cents over mid-grade.

flthere

iTrader: (2)

Ya even I noticed exactly dr-rjp said when I switched from premium to mid-grade. I said enuf of it and then switched back to premium ... what a relief !!! I drove for just 30 miles on premium after 3 tanks of mid-grade before it and I can feel the difference ...

SilverMax_04

Both of you have 98s and I have an 04. I suspect we are either seeing a difference between the two different year's VQs or you two have more engine deposits, boosting their octane requirement.

I don't know enought about the older VQs by year. Are your engines 3.5 L or 3.0 L?

flthere

iTrader: (2)

3.0l one ... it's an I30

yaa, when i opened the oil cap the other day, i am not surprised to see kinda sludge ... i just ordered auto-rx hopin it would clean it good enuf But ya the premium did bring back the power ... i know the engine will run perfectly alright with the regular and plus grades but definitely it loses power for sure.

i'm sick of that shift shock but we once had a lengthy 5 or 6 page thread on that 1-2 shift jerk, conclusion in general was that nissan's auto transmission (4th gen) sux. Some others said sthg abt bad coils, some sensor related to tx or 'abt to die' tx etc., I gotta read thru the stickies to see how to test those coils ...

SilverMax_04

The torque in the 3.5 VQ is awesome. If I don't get engine knock, there is ample power in this engine. I burn regular here (85 octane) and only get light engine knock when climbing hills when the temp is over about 75 degrees F. My solution to this is to keep the engine RPMs above 2 K and the light knock will go away.

Guess if I had a 3.0 I'd be bruning premium too.

dr-rjp

iTrader: (4)

Besides the engine, there is a world of difference in the electronic engine management systems from 1998 to 2004. I'd dare to say that it is the major factor between our rides with respect to how we handle octane.

When our timing is backed off to meet the lower octane, we have fewer ponies to spare than an '04. The shift thing is affected by the timing as well, and I suspect it will smooth out once the electronic modules adapt.

BTW, I had the cover off to replace a gasket, and there's no sludge or carbon deposits to be seen down there. I may need a new O2 sensor or two, though.

Still, the car is perfectly drivable, but not as enjoyable.

SilverMax_04

The deposits I'm talking about are inside the engine' cylinders -- not in the oil (which you are talking about when you mention sludge). These deposits tend to occur on the spark plug and the valves in each cylinder. They also occur on the fuel injectors. Engine deposits increase that engine's octane requirement two ways:

- Because they occupy space, deposits increase (just sligltly) the engine's compression ratio.
- Because they are located where they get hot from burning fuel, and because at low RPMs they don't get proper cooling; deposits have a tendency to glow and cause engine knock (premature fuel burning).

Proper doses of fuel injector cleaners (like Techron) will clean the deposits from the injectors and generally do a good job on the spark plugs and valves.

dr-rjp

iTrader: (4)

Right...forgot about that. The plugs looked clean when I took a look at them, but cannot vouch for the cylinder head or walls.

However, I have been running either Chevron or BP premium up until this tank, I probably have a pretty clean engine.

So far, I cannot tell any difference between 87 and 93 with respect to idling, cruising, and normal acceleration (which I define as keeping upshifts below 3,000 RPM and gas pedal travel below 1/4 of the way down).

Where I do notice a major difference is in upshifts (1st to 2nd above 3k) and downshifts (4th to 2nd). The feeling is analogous to running with ankle weights on.

I still get to where I need to be, but it takes longer to do so. For example, when merging onto the highway, I have to keep the car in lower gear longer to get ahead of the oncoming traffic.

The timing on the car is retarded, and consequently, so is the acceleration. There need be no other explanation for it.

SilverMax_04

Based on your experience, I think we can conclude that most 3.0 L VQs should probably stick to burning Premium.

I suspect you are correct about engine deposits if you mainly use either BP or Chevron. Both (I think) have continued to use a higher treat rate in their Premium.

dr-rjp

iTrader: (4)

Remember that smell I mentioned (of raw gas) the last time I tried using regular?

Well...it's b-a-a-ack!!

SilverMax_04

Is the smell back burning Premium? Sounds like you have a gasoline leak.

dr-rjp

iTrader: (4)

The smell occurs only on a cold start-up...from the exhaust, and only when I run regular.

I've never had that smell running on premium. I recall you mentioned that there may be sulfur components in regular that are not present in premium.

But, if you ask me, I think it is because my car takes a lot longer to turn over in the a.m. running on regular than on premium, and it could just be an accumulation of unburnt fuel/air mixture in the manifold that gets blown out the pipe when I finally get ignition.

If I had a carb, we'd call it a case of it getting flooded. Right?

Any other reasons?

SilverMax_04

There are sulfur compounds in all grades of gasoline, but the premium tends to have less sulfur than the regular. If it were sulfur, the smell would be like rotten egge, not gasoline.

High octane means that the gasoline does not burn as easily, so it should be easier to start the engine burning regular than burning premium.

Also, any unburned gasoline should be handled by the cat converter. When the engine (and converter) is cold, this is not very effective. When warmed up, the cat converter eliminates it all (if it is working properly).

Suggest you go back to burning premium. I expect you will continue to get this smell. You are probably correct that you are experiencing a slightly flooded condition on cold start. You may need to have the ignition system checked to be certain it is operating properly. You could be running rich and only smell the gasoline when the cat converter is not burning it up.

kklier

Since mid August I started running 87 Octane. I stopped paying for 93 octane when it went above $2.50/gal.

I drive about 15-20% City and about 80% highway and I get between 24-25MPG. I have been keeping the RPMS below 3k and most times I try to keep the rpms between 2-2.5k.

Since I am keeping my RPMs low I tend to be in a 5th or 6th more at low speeds. At these lower RPMs I do hear more knock, but that is the only time.

On the occassion that I decide that I need to nail it in first and shave a bit more rubber off the front tires I still have plenty of power to put a grin on my face.

SilverMax_04

The only time I get light engine knock (burning regular) is when the engine RPMs fall below about 1900 RPMs while I am climbing a hill (which I do when I drive home). Therefore, I try to keep the RPMs above 2 K on the hills. I also try to keep the RPMs above 2 K when cruising on level ground (except when rounding corners) just for knock safety.

I too have ample power for fast acceleration in all 6 gears, I just need a gear where I can get the RPMs above 3 K quickly -- where the real power is.

dr-rjp

iTrader: (4)

Hydrogen sulfide, yes. I should have stated that what I smell is not actually gasoline, but a stinky exhaust that is not present when I'm running premium.

All things being equal, maybe. But, the timing is not the same, and that is something to consider as well.

Could also be the fact that my new Y-pipe has no pre-cats. Also, does it matter that the O2 sensors are offline at cold starts?

When the car is warm, there is no smell.

Good suggestion. I definitely will not use 87 octane again. I might go back to a 50/50 blend of 89 and 93, though.

SilverMax_04

Possibly true. With regular the timing would be retarded. I'm not certain if this would make it harder to start, or not.

These sensors being offline could result in the air/fuel mixture being richer, resulting in more unburned gasoline that the cat converter does not handle well when cold. When warm the mixture is correct and the cat converter is working. Make sense to me.

I think the conclusion I've come to is that if you have the 3.0 L VQ engine, you probably should not plan to burn regular (87 octane) on a regular basis. Mid grade (89 octane) may work, check it out. Premium will give your engine maximum performance. This smaller engine lacks the torque and power of the 3.5 L and so needs more help being a top performer. The higher octane gasoline helps accomplish this.

dr-rjp

iTrader: (4)

IMHO, 87 octane is like decaffeinated coffee, sugar-free chocolate, non-alcoholic beer, and abstinence. Maybe good for some, but not for me.

SilverMax_04

Go for the Viagra Gasoline in the 3.0 Liter VQs!

dr-rjp

iTrader: (4)

Ah, yes, that little blue pill called Sunoco 100 octane...

Haven 't priced it lately, but the front door to the Sunoco station has three logos on it:

VISA
MASTERCARD
DITECH

SilverMax_04

If your car was designed to burn 91 octane gasoline (even with engine deposits adding a few octane numbers), then 100 octane gasoline -- assuming it is truely an (R+M)/2 octane and not just a Research Octane -- will not be worth the added money you will have to pay over a 93 octane gasoline. Don't pay much more for something that will not have the benefits you are paying for. Suspect this fuel is for turbocharded engines.

dr-rjp

iTrader: (4)

No worries, here. The stuff sells for twice the price of 93 octane, so even if I wanted to use it, I couldn't afford it.


Well, the great 87 octane experiment is over. I threw in a can of Seafoam and filled it back up with 93 Chevron.

Now, my car drives like "Where ya been?"

NismoMax80

iTrader: (6)

so can we just bring this to a close:
if you use 87, you hate your Max.
if you use 93, you love your Max and she will love you back.
if you use 91, you and your Max get along.


ok, real conclusion: You get what you pay for. Since Maxima is designed with Premium in mind, you'll reap benefits from using it. You can be cheap, but you will notice.

SilverMax_04

I must really hate my Max, I burn 85 octane (at 6 K feet elevation).

I don't agree with all of your "real conclusions", either. I do agree that the VQ engine was designed for maximum performance burning Premium. But it was also designed (at least the 3.5 L VQ) to perform adequately on regular gasoline. I've been cheap in the past (most of the time) and have not noticed the difference.

My conclusions:
- In the 3.0 L VQ engines, stick with Premium.
- In the 3.5 L VQ engines, burn the gasoline that meets your performance expectations. For some that will be Premium, for others that will be mid-grade, and for still others that will be regular. Try them all out (the Max will perform adequately on all) and make your own decision.

I should point out that this coming December & January I will conduct a test to determine if the 3.5 L VQ in my Max will get enough better mileage burning Premium while driving on the expressway to justify the higher price. If that test shows that Premium more than pays for itself in better mileage, I will consistently burn only Premium on the highway (but not around town). And I will report my results in a new thread on this site.

Bobo

You, sir, are a cheapskate and obviously performance means nothing to you at all! Buy a Prius, Echo or Smart Car and count your pennies ad infinitum.

Just comparing fuel economy of 85 octane vs premium is a meaningless exercise because it accords no merit whatsoever to performance, acceleration etc.

Perhaps 85 octane is permissible at 6K feet but one would have to be retarded to use anything below 89 at lower elevations with a 10.3 to 1 compression ratio.

SilverMax_04

If performance meant nothing to me, I would have bought a 4 cylinder Honda or Altima (which my wife wanted). I bought the Max, and am getting the performance I wanted with regular gasoline. I had a rental car (paid by insurance) when the Max needed some body work. It was a dog. I was happy to get my Max back with the great performance. Will I race her -- not very likely. Do I need Premium if I race her -- you bet. Do I need Premium for driving around town -- NO.

Am I cheap -- you bet. But I hate to waste money buying performance I don't intend to use = WOT (Wide Open Throttle).

Bobo

I have seen a post by SteVTEC in the past week or two that refutes your contention. He is one of the most knowledgeable members on this website and his recommendation is to run premium in the city, and lower grade gasoline on the highway for optimizing gas mileage. This flies in the face of what you state.

It appears that image is more important to you than performance.
At the end of the day, I side with your wife, not you!

SilverMax_04

I havn't seen a posting from Steve in months.

If image is more important to me, then I would be burning Premium -- all the time. It isn't and I don't.

I do not normally burn Premium on the highway. I was told that I might get better mileage burning Premium on the highway, so I will check to see if the higher cost of Premium is more than made up by better mileage -- to give me a lower cost per mile driven than I get with regular. I did a very small Premium test last summer that said I got the same cost per mile driven with both Premium and regular. But the test needed to be longer. I drive to Chicago in December and come back in January. I will drive out on the cheapest gasoline (in Iowa mid-grade with ethanol is cheaper than regular) and drive home on Premium gasoline. That should be enough of a test.

So you are going to buy a 4-cylinder Honda for your next car.

Bobo

You have read me dead wrong! The image is not the premium vs regular gas it is the trophy car! I commented at length about the "test" you ran. Remember I was the one that audited your data and pointed out that you didn't even give the premium a chance. You ran premium for less than two full tanks, IIRC, and I believe the premium was a blend of premium and almost an equal volume of lower grade gas, so you didn't even run a full tank of premium the whole trip.

If you are going to run a test you require giving the premium a decent chance. This involves running it for a few tanks just to get the ECU to adjust to the change in octane properly.


I suspect that my 61K, mostly highway miles, 95 Maxima SE with a 5-speed tranny, Budget y-pipe and K&N panel filter, running Chevron 92 gasoline (94 is available but who cares) would outperform your 6th Gen in the 1/4 mile, stop light to stop light or on the highway if you were running 85 octane, and if it couldn't it would be a close 2nd.

Keep up the image!

SilverMax_04

Wrong. I don't have a trophy car. I have the car I went out to buy: A 4-door sedan with a 6-speed manual trannie coupled to a modern 6-cylinder engine. I considered the following before deciding on the Max: Honda Accord (no manual trannie except in 2-door coupe or with 4 cylinder), Mazda 6 (their engine is not the most modern technology), Toyota Camray (manual only available with 4 cylinder), Volvo (too much money for a smaller car than the Max), and Altima (very close, but I liked the ride of the Max and the extra gear in the manual trannie).

I would never try a race in my Max without burning Premium to get the top performance. I don't race, and don't normally burn Premium.

2002 Maxima SE

iTrader: (3)

Just make sure to replace you knock sensor regularly...I'm sure it is getting quite a workout.

SilverMax_04

The knock sensor is doing what it was designed to do. I've yet to be convinced that burning regular will wear it out any faster than otherwise would be the case. I can even make a case that burning only Premium will cause the knock sensor to freeze in place and not be able to adjust for changing situations (gasoline octane, high heat, higher elevations, etc). I won't have that problem because I burn 85 octane in Colorado and travel east at least twice a year where I burn 87 octane in Nebraska, 89 octane in Iowa, 87 octane in Illinois, etc.

Bobo

Why don't you try filling up with 91 or higher about 500 miles before your next road trip and again along the way and continue that process until you get back home? You can then go back to your cheapskate ways and have a fleeting memory over time of what real Maxima performance was meant to be!

What will the incremental cost be - maybe $20 or $30 or so at the pump, offset by improved fuel economy, and a silly grin on your face when you put your foot to the boards to pass someone! Be a man and try it sometime.

SilverMax_04

I don't mind being called a cheapskate. But to go after my manhood??

The VQ has ample passing ability burning regular -- and how much do I need on the interstates? I will stick to my planned test this winter to determine if I can lower my cost per mile -- which is all I care about given the VQ's abilities on the highway. If Premium provides such superior performance on the highway, I will know about it on my trip home in January. Doubt I will notice any difference. All reading this need to remember that the 3.5 L VQ (in my 04) has much more torque (and HP) than the 3.0 L -- even burning regular.

Bobo

It takes a lot to get your attention, lol! As I said before give the experiment a fighting chance. Mixing two tanks of lower octane fuel with higher octane fuel hardly counts. You know d@mn well you have to run the premium for awhile to make a difference so at least start with an empty tank before you fill it up with premium, not a half a tank like in the summer. Then run a few tanks of premium. Last time you didn't even give it a fighting chance and posted all that ridiculous data. As I said I audited it. As an **** retentive accountant I enjoy those things. You know, its kind of like some people enjoy buying 85 octane gas for their 10.3 compression ratio 3.5 litre DOHC engine.

I don't know how you get off saying its just fine to run regular for a 6th Gen Maxima, but a 4th Gen should use premium. That assertion is absolutely retarded!

2002 Maxima SE

iTrader: (3)

Even though the knock sensor can retard timing, it can not change the compression. I wonder if there is any damage that can occur, long term, by not using 91 octane?

SilverMax_04

Bobo, you sound like a man who needs the last word. This will be my last on this subject until I do a new post in January on my Premium test. I said the 3.0 L VQ needs Premium because of reports from others on this post who reported poor performance with regular. It was their position, which I did not dispute (never having owned one). Have you ever owned a 3.5 L VQ? and driven it with regular? If not, then believe my experience -- like I believed the 3.0 L VQ owners.

I do my best when I go to Chicago not to buy gas there because the "botique" Chicago area gasoline costs about 30 cents or more than what I have to pay in Iowa. So on the trip home I will hit Iowa as close to empty as I dare run the Max. That's when I will fill up with 93 octane Premium -- almost an empty tank. I will buy Premium at one more stop in Iowa and two stops in Nebraska. I get home with about 1/3 of a tank remaining. At home I will go back to my 85 Octane regular again. The test will be over.

Talking about compression ratios, the Honda Accord V-6 has a 10.0 to 1 compression ratio and recommends Regular gasoline. The new Nissan Maxima has a 10.3 to 1 compression ratio and recommends Premium, but advises that Regular gasoline will perform adequately (and 85 octane at above 4 K feet). Its in my owers manual and my 38 K miles on the Max confirm this to be true. How big a difference can there be between two engines -- both with the most modern engine technology -- and only 0.3 difference in compression ratios? Nissan wants the best possible performance so they have 0.3 more compression ratio and recommend Premium. Honda wants to be more frugal (economic) and recommends Regular. Difference in target buyers, but not much difference in engine technology. (If there were, you will be hearing from Stevetech on this subject.)

Finally, unlike many on this site, I know something about octane, having worked for an oil company for 35 years. If you don't believe me, simply check out my long thread on the subject on this site:

http://forums.maxima.org/showthread....6&page=1&pp=30

I know what factors influence the need for octane, and frequently see the combination of heat and load factors cause me to downshift to eliminate slight engine knock when pulling the hill to my house. I know you will say that if I were burning Premium, I would not need to downshift. But a downshift in the 6-speed is easy, and it reduces wear on the engine from a tendency to lug it when running below 2 K RPMs while pulling a hill when the temps are in the high 70s or above. It never has slight engine knock above 2 K RPMs in this situation.

2002 Maxima SE

iTrader: (3)

Thats all well and good, but you're not an engineer. You did not build the Honda or Nissan engine nor did you decide what the octane ratings would be. Neither did I. Your opinion is just that and no more valid than anyone elses. We don't know if Honda recommends low octane to get you to buy another vehicle in 10 years and we don't know if Nissan recommends high octane because of an internal joke.

Of the 3.0L, two drivers mentioned pinging on 87. Two. There are hundreds of thousands of 3.0L Nissans on the road, so saying that because two have pinging/bad performance on 87 does not a conclusive statement make.

What we do know, and are facts, is that:
1)Nissan recommends high octane, but you can use regular when premium is not available. Not the other way around.
2)This is a high compression engine which for many years has meant a high octane is needed.

Bobo has a point about the premium test. You have to run more than a half a tank. However, if you're fine with running regular all the time, just do it. No reason to justify it. Maybe you make it 200k and maybe you don't, but I follow the engineer recommended octane.

Bobo

There is something wrong with this picture. I believe SilverMax04 is an engineer and I'm a cheap lowly accountant trying to tell him to spend his money. I give up. I do know you can get by on lower octane fuel at higher elevation, but I don't know that I would ever run 85 octane in a VQ engine. I have never used anything below 89 octane and am presently using 90 octane marketed by Husky Oil at 87 octane prices. I have never used 91 octane, but have used Chevron 92 octane. We have no 93 octane here, but do have a number of stations that carry 94 octane.

I really can't tell much of a difference between Husky 90 and Chevron 92; 94 octane would be overkill. Next summer when I take my annual road trip to the Interior of the province and have to climb from sea level to over 6,500 feet, I will use 92 octane.

I can hardly wait to audit SilverMax04's data. I suspect he will have once again run premium gas at most 20% of the time and again be filling up at half a tank because he has found some bargain basement price on 87 octane.

Regarding Honda engines, I have a friend with a 98 VTEC Accord and I believe his compression ratio is only 9.8 to 1. The manual calls for regular gasoline but the engine has no knock sensor. It puts out 200 hp and I could smoke him any day of the week.

One penny, two penny, three penny, four!

SilverMax_04

Just as you point out that I should be careful about what I say, so should you. I am an engineer, a mechanical engineer who worked for Amoco for 35 years. I do know something about octane. Correct, I did not build those engines, but I know about them. They are both built with the most modern engine thechnology available -- unlike most of the iron from Detroit. They will do what their builders say they will do. I will quote from the 2004 Maxima Owners Manual:

"FUEL RECOMMENDATION
Use unleaded regular gasoline with an octane rating of at least 87 AKI (Anti-Knock Index) number (Research octane number 91).

For improved vehicle performance, NISSAN recommends the use of unleaded premium gasoline with an octane rating of at least 91 AKI number (Research octane number 96)."

I left nothing out of this recommendation it is all here. The book goes on later to discuss burning 85 octane Regular "in high altitude areas (above 4,000 feet) . . ."

I suggest you read my posts on Octane and learn something before spouting off. See my post above for the link to these earlier posts. Also see why the rest of the world still uses Research octane number rather than the number used by the US and Canada (R=M)/2.

Bobo, when I was shopping for a new car in the spring of 2003, the Honda Accord had a 10.0 to 1 compression ratio. I believe the current one still has that ratio. Older Maximas have lower ratios than 10.3 to 1 -- but I was comparing what I believe are their current ratios.