Re-Tuning G35 engines to run on lower Octane

[Davgreg]

Hey all. This is my very first post in the Forum. If I had known it was here I would have been here a long time ago. Quick review of the posts and its seems most of you are on top of your game.

My question is this: I was looking through a motortrend and they had an advertisement for a company that sold performance parts (nothing new here.) The thing that caught my eye was the engine re-tuner that would make your engine more fuel effeicent. Is this possible for the G35's and specifically a 2003 G35 Coup?

I was thinking of doin this cause the wife is driving it during the week to work (20 miles round trip) and thought I'd reduce the Octane need until I reclaimed my baby.

Also the article on changing the sparks early cause the stocks wear out long before the manufacturers claim of 80k-100k makes a lot of sense. I think I will look into that.

anyway what are all your thoughts?

Dave

[rn79870]

Welcome to NICO. I think the answer is that the computer has some intelligence as far as retarding timing for lesser fuels goes, but I wouldn't chance it. I know this has been discussed here before, and it might be worth it to search the entire site (the search button at the top) for info from this and other related foruns (350Z, etc). Oh, you for got to post pics of your ride...

[joe603]

Welcome!!

I haven't heard of this one...Usually retarding the timing will allow you to run lower octane fuel...That's probably what this thing does.

[gwoods]

Retarding timing AND ADDING FUEL to richen the Air/Fuel Ratio.

You'll spend about the same on gas and not have the performance...

Higher octane gas burns longer....

The cost of this tuning ect...

I'd just leave it stock.

[AZhitman]

Lower octane fuel costs $ .05 - .10 less per gallon.

That's $.80 - $1.60 per tank you'll save.

Subtract from that savings the lower fuel efficiency of lower octane fuel (based off the ECU retarding timing), and you've saved.... Nothing.

It's fine the way it is. Let your wife drive it with the "good stuff".

p.s. WELCOME ABOARD!!!

[telcoman]

Lower octane fuel costs $ .05 - .10 less per gallon.

That's $.80 - $1.60 per tank you'll save.

Subtract from that savings the lower fuel efficiency of lower octane fuel (based off the ECU retarding timing), and you've saved.... Nothing.

It's fine the way it is. Let your wife drive it with the "good stuff".

p.s. WELCOME ABOARD!!!

Hello AZhitman

I disagree with your math.Here in NJ the difference in price between regular 87 octane and premium is $.30 per gallon. I drive 24k miles per year divided by an average 22MPG equals 1090 gallons. 1090 gallons times $.30 equals an additional $327.00 per year. I'd rather have that in my pocket & not further enrich the oil companys.I know there have been many posts and disagreements on this topic, but for my $.02 I believe for most drivers regular 87 octane is fine. For those that race that is an entirely different story.I've never heard a ping out of my engine and cruise between 75 & 80 MPH.My best mileage on a single tank of gas using regular was 28.88 MPG between Va and Ga on a trip to Florida. With just over 48k miles my G runs just fine.I don't like the wife driving my car.

Telcoman

[itgogitrev]

This is straight from a former technician

Newer cars can pull back timing via the ECU. It's not a big deal to put 87 oct in your car. However, I don't think you're really saving yourself that much money. I record my mileage for every tank of gas and divide it by how many gallons it takes to fill it up. I notice that I do seem to get at least 2-2.5 MPG more with 91 oct.

I don't beat my car. In fact, I have a relaxed drive to work where I'm only doing 55-60 on backroad routes and I keep it in Top Gear the whole time. There is a difference between 87 and 91 oct gas mileage. My current car is 12 yrs old, is a 2.9L 6cyl with 10.5:1 CR and is turbocharged. The ECU (which has stock ignition and boosted fuel mapping) was built to retard timing the same way as the stock one would. Since my car is a decade older than most of your cars, I don't see the problem with running 87 every couple of tanks.

[gwoods]

87 octane MAY not hurt your engine the same way 16,000 mile MOBIL 1 oil changes MAY not hurt your engine.

http://neptune.spacebears.com/....html

[Rivalry]

87 octane MAY not hurt your engine the same way 16,000 mile MOBIL 1 oil changes MAY not hurt your engine.

http://neptune.spacebears.com/....html

"Engine wear actually decreases as oil ages. This has also been substantiated in testing conducted by Ford Motor Co. and ConocoPhillips, and reported in SAE Technical Paper 2003-01-3119. What this means is that compulsive oil changers are actually causing more engine wear than the people who let their engine's oil get some age on it."

Telcoman... be careful!

[smockers83]

The cost/benefit of retuning your engine to be able to save 30 cents a gallon may interest you. Figure that out and you'll have an answer.

But octane level is based more on compression ratios than engine management systems, so you have some things to think about.

Changing oil every 3000 miles is pretty standard in the industry, not compulsory. That's generally the life of an oil (dino oil that is).

[telcoman]

"Engine wear actually decreases as oil ages. This has also been substantiated in testing conducted by Ford Motor Co. and ConocoPhillips, and reported in SAE Technical Paper 2003-01-3119. What this means is that compulsive oil changers are actually causing more engine wear than the people who let their engine's oil get some age on it."

Telcoman... be careful!

Hello Rivalry

Rest assured, I am careful.

If I'm not the oldest NICO member driving a G35 6 speed stick I'm probably pretty close? With over 40 years of driving experience with many different vehicles my personel experience does not agree with your assesment.Ive gotten 246k miles on a 1980 Diesel Rabbit in 17 years , over 200k on a 1988 Mazda 929 5 speed stick over 14 years, over 150k miles on a 1974 Mazda RX4 Rotory engine over 18 years , 125k miles on a 1992 Lexus ES300 5 speed stick over 13 years. All had oil changes every 3k to 3.5k miles and I used regular 87 octane in all of them. Similar aguments were heard back in the 1970's during the changover from leaded fuel to unleaded.Not changing oil every 3 months or 3k miles will result in a sludge buildup in your oil pan. The normal heating and cooling of an internal combustion engine allows water vapor to become mixed with the oil. Over time this mixture becomes harmful to an engine as it turns to sludge. Changing oil is not a waste of resources because motor oil is recycled and reused. INMHO spending $6 bucks per quart for synthetic oil and then not changing oil regularly is more harmful to a pocketbook as well as an engine.To the younger members of NICO driving perhaps their first vehicle and having little experience in maintenance I just offer my personal experience. They can make up their own minds.I do not believe everything that is written in owners manuals or advertising in both print and TV. I read consumer reports, listen to Car Talk. I then make up my own mind. Car & Driver, Hot Rod, and other magazines rarely have real objective articles because they accept advertising and don't want to offend the hand that feeds them so I don't bother reading them.On required octane for example, after reading my owners manual for the first time 2 years ago, I conducted an experiment.My G35 delivery came with a full tank of fuel. Assuming that the dealer delivered the car with premium, when my fuel gauge reached the 3/4 mark I filled up with regular 87 octane. I noticed no difference in performance. When the gauge reached the 1/2 mark I again filled up with regular. No noticable difference in performance. When the gauge reached the 1/4 mark I again filled up with regular and noticed no difference in performance. I've been using regular ever since.

Oh, did I forget to mention my first vehicle, a 1958 $ucken Ford. That was my first & last Ford Had it three months. I should have listened to my father.

Telcoman

[zozoka1212]

Oh, did I forget to mention my first vehicle, a 1958 $ucken Ford. That was my first & last Ford Had it three months. I should have listened to my father.

Telcoman

My old Telco brother 06 they were close to the bankrupcy you never know they might go out of business if they keep up this way. All these new fords they came out. They all fugly.

zozo

[!979TransAm]

Something else to think about, Pinging is not the only signal of engine damage. "pinging" can occur without you even hearing it. I have seen quite a few high compression motors shake apart because people think they can hide static compression with camshafts and timing, WRONG. Detonation can occur even when not heard.

You save 370 bucks BUT what could it cost you if something goes wrong? A lot more.

[rn79870]

The manual for the 08 G35 is also the manual for thew 08 G37. It states that for the G35, it is okay to use lower octain when the correct octain is not available. For the G37 the manual specificaly states that the owner should only use the minimum necessary to get him to another fueling station where the correct gas grade is available.

I have to agree with TransAm that all signs of detonation are not immediately detectable. But I am not a mechanical engineer either.

[Davgreg]

WOW. Big discussion for sure. Thanks for welcoming me and all the honest opinions.

As for me I baby my G35 and I run synthetic oils all the way round (inlcuding the transaxle.) I have 50,000 miles on it. My wife gets to drive it cause of her proximity to the house and the fact that I HATE to sit in traffic in it.

Gas here in Miami FL is $3.30 premium (93 octane no lower premiums available like 91.) its $2.90 for 87 octance. If the wife is only driving it 30 miles tops I just didn't want to spent more money if at all possible.

And I noticed nobody mentioned Octane boosters, which I have no idea about either.

So what should we say? "It maybe bad or it may not matter but its up to the owner."

[rn79870]

[QUOTE=Davgreg].And I noticed nobody mentioned Octane boosters, which I have no idea about either.QUOTE]

Octane boosters just increase your fuel costs and are not needed. If you research the way you get 104 octane from one that advertises that octane, you need to do more than simply add it to the tank. You have to blend the fuel (or at least that is the way it was in the past).

Gas is $3.17 prem. $2.97 reg. at Costco here.

[telcoman]

.And I noticed nobody mentioned Octane boosters, which I have no idea about either.QUOTE]

Octane boosters just increase your fuel costs and are not needed. If you research the way you get 104 octane from one that advertises that octane, you need to do more than simply add it to the tank. You have to blend the fuel (or at least that is the way it was in the past).

Gas is $3.17 prem. $2.97 reg. at Costco here.

$2.75 for regular here in Central NJ today. Dropped $.02 from yesterday

[Sentientbydesign]

In the end, we all come from different backgrounds. Our financial situations and those of our parents make huge differences in what we buy.

I can't afford it at the moment, but I will be doing a complete Amsoil change over on my G35 coupe.

Average fuel economy savings are in the neighborhood of 4% with some reaching as high as 7%.

I sincerely believe that "you get what you pay for" is true for 85-90% of products.

Telcoman and I are on completely polar sides of this debate.

I hate BP gas. I think their cheap $#IT is as good for me as it is for my car. Same for cheap oil. I HATE changing my oil. I work too damned much to have to lift my car and have dirty lubricant come flying out at me ever 6 weeks.

Amsoil has been around for over 35 years. They make synthetic oil specifically designed to reduce wear and promote longevity. I can spend $10/quart and get 7-11 times the duration in oil changes.

So I can change the cheapest oil out there every 3k miles (maybe sooner if I push the car at all and the oil starts shearing) and pay around $7.50-$10 in oil per change. Or I can dish out $50 for oil, but not have to change it for 12-18 months and I pay between $4.50 - $8.50 per 3k miles PLUS get better fuel economy and cold start protection.

As far as tuning goes, which is the point of this thread, I strongly believe that a stand alone Engine Management could be programmed to run our cars leaner and to also limit or prevent WOT for fuel economy.

Now, why would I want to do that when I have a pseudo-luxury sports coupe? Well 1) would be to stop me from needlessly wasting gas. 2) would be to help me save money so I could spend it on stuff like stand alone EM systems, plenum spacers, and CAIs...oh and lets not forget those lovely tires too.

[telcoman]

In the end, we all come from different backgrounds. Our financial situations and those of our parents make huge differences in what we buy.

I can't afford it at the moment, but I will be doing a complete Amsoil change over on my G35 coupe.

Average fuel economy savings are in the neighborhood of 4% with some reaching as high as 7%.

I sincerely believe that "you get what you pay for" is true for 85-90% of products.

Telcoman and I are on completely polar sides of this debate.

I hate BP gas. I think their cheap $#IT is as good for me as it is for my car. Same for cheap oil. I HATE changing my oil. I work too damned much to have to lift my car and have dirty lubricant come flying out at me ever 6 weeks.

Hello Sentientbydesign

Very true what you say!That is what makes this site interesting. Lots of different opinions. For the newest members they can read the posts and make up their own minds. Funny that you mention BP gas. That is what I mostly use because it is generally the cheapest, closest to my house, and the guy doesn't hassle me when I pump my own gas. To those of you that have never been to New Jersey, NJ is one of only two states that actually have a law on the books that states only gas station attendants can pump gas.This oil and gasoline debate is almost like listening to Republicans vs Democrats?Gotta go now! Its almost time for Hardball with Chris Matthews on MSNBC.

Telcoman

[Sentientbydesign]

I was very surprised on my first trip to Oregon when I was told that I couldn't pump my own gas.

I started wondering if I was supposed to tip the attendant too

[telcoman]

I was very surprised on my first trip to Oregon when I was told that I couldn't pump my own gas.

I started wondering if I was supposed to tip the attendant too

Only if they wash your car You have to get out to make sure they put your gas cap on properly.What pisses me off is most of them will just let the cap rap against my car instead of placing it in the holder. So I just get out & do it myself. Just like my oil changes.

Telcoman

[C-Kwik]

And I noticed nobody mentioned Octane boosters, which I have no idea about either.

Octane boosters do almost nothing. by the time you mix it with the gas in the tank, it becomes so dilutred that the increase in octane is negligible. in other words, don't bother with them.

As for the original topic, using regular unleaded likely won't kill your car. The manufacturers designed the car to be able to handle the lowest octane fuel available. Just don't expect the same performance or per gallon fuel efficiency. I don't know how much of a hit in fuel efficiency you might see, so it's hard to say what kind of impact it will have on the $$$ per mile factor.

[rn79870]

I started wondering if I was supposed to tip the attendant too

TIP: Don't scratch my car!

[Jacko3]

To Telcoman and SentientBy Design:

These are my experiences so far. I have a second car, a Nissan with over 200K miles. I realized that octane rating was a waste of money for the car as regular 87 was just about right. In fact, I found that the specific marketers gas was more of a factor in pinging and driveability than the octane rating of the gas. My engine was about to quit at one point because of I was using QT and KwikTrip gas. So, in 2001, i switch to BP gas, and I ahev zero problem with the engine till this day.

In my G-35 coupe i also use BP gas. If I had more money, i probabaly would do Chevron gas. While I have not tried it yet, I happen to beleive that BP and Chevron 87 Octane gas might even be as good as Quiktrips 91 Octane rating, only for the reasons of the additives added to their gas.

As for oil, I have synthetic in G-35. I only used synthetic only for the purpose of ensuring that my engine has little deposits in it, and that the engine stays relatively healthy for much of its life span. synthtic or no Synthetic, i will not allow my oil to ever go past 3,500 miles before changing it. The synthtic is just a guarantee that if I exceed 3,000 miles before an oil change, that i am still good. Synthetic makes a difference during start up and during acceleration. My car warms up pretty quickly as well. And then, the most surprising thing about the synthtic is that after hard driving, when I get home, the engine is barely hot or making that ticking heat expansion noise when parked. I have used all threee oils in the G_35 Coupe and Synthetic is the very best.

The only issue I have always been worried about Synthetic is the problem of oil consumption, especially for a few who use Mobil 1 Syntec. Well, it seems those engines that burn oil, while using Mobil 1 Syntec, already had issues to begin with. A good modern day engine should burn little or no oil between oil changes, regardless of the oil you use.

I do not beleive that the octane rating has anything to do with the internals of your car. Rather it has a lot to do with the amount of energy produced in the cylinders. Of course, higher octane rating will create more compression and energy and thus, the right amount of strokes, for combustion--ECU will recognize the amount of strokes while doing less work to mix the right amount of air and gas. Thus, higher horsepower. Thus, you will use less gas per mile and get slightly more power with higher octane ratings.

The lowest octane rating will produce the least amount of energy, and perhaps an irregular amount of strokes for combustion--which may cause pinging, and will cause a slight confusion of your ECU when mixing the right amount of air and gas. Because of the lower energy levels in the cylinder, your ECU will compensate as it will cause your fuel pump to deliver more gas to meet the engines combustion energy requirement in order to deliver the preset amount of strokes as programmed in your ECU. So, you will use more gas per mile when you use lower octane ratings.

Both grades of gas will do absolutely nothing to the mechanical state of your your car. However, the lower octan rated gas, may cause other systemic problems due to the irregular nature of the amount of energy the engine will produce, and this is a result of the preset measurements based on pre-determined energy production in the cylinders as detected by your ECU.

In essence, your car is literally run by your ECU. A confused ECU is like a crashing laptop computer, and it will continue to compensate for irregularities up till a certain point, before it starts acting out and causing other systems in the car to go crazy, and then one day, it will blue screen like every Windows Operating system. A car is a system, and so, it must be viewed in that light to understand how one part of the system affects the other parts of the systems.

If you drive gently and don't push your car, low octane gas rating is about okay--the confusion your ECU experiences won't be that extreme or bad enough to cause major issues later. If you drive hard and if you push your G, please and please use the highest octane rating or whatever the manufacturer recommends in your G.

Infiniti actually built the G to be pushed hard, and so they cannot recommend a low octane rating. It would be irresponsible for them to do so, knowing fully well that it is those with lead foot that are buying their cars. One easy way to destroy a high performance engine is to drive it hard all the time but use the lowest octane rating all the time or the lowest type pf oil available. This will cause the engine harm, not immediately, but over time.

The immediate effects of using lower or higher octane rated gas is not always evident. The evidence lies in the confusion of the mind of your car--the ECU. You can choose to drive normally and gently, while using a low rated octan gas. Or, you can choose to drive fast and furious while using a higher octan rated gas. If you use low octane gas in your G for hard charging driving, you will cause other systems to fail in your car, to include pinging. If you use high octane gas for daily normal driving everyday, you are wasting your money and time.

I drive my G like I stole it every other day (5,000RPm to 6000RPM is routine) since I have the other daily driver, so, I can't afford to skimp on gas or oil quality. I have to use to the best.

And if your moded your car, please, take time to get the ECU reset after each mod. Your car will thank you for it in the end. When you add new parts to your engine, without re-programming the ECU, you are going to confuse ytour ECU. A confused ECU is a bad thing for your car, since the ECU literally runs the car. And, a confused ECU will destroy something on your car, either sooner or later.

A word is enough for the wise.

[justjuiceit4]

On required octane for example, after reading my owners manual for the first time 2 years ago, I conducted an experiment.My G35 delivery came with a full tank of fuel. Assuming that the dealer delivered the car with premium, when my fuel gauge reached the 3/4 mark I filled up with regular 87 octane. I noticed no difference in performance.

Telcoman

That was a huge assumption on your part! I worked at dealership for a summer job and they put 87 octane in everything! I was driving a 3000GT twin-turbo and I was like, "this thing is not all that." Even though there are "Premium fuel only" stickers all over the place, the salesperson before sure enough filled it up with regular.

Another example is a rental Maxima that I got. To save money, they fill everything up with regular. At the time, I had a Nissan truck and they would not let trucks race at this event, so I did the next best thing! Knowing I wanted to get the maximum performance, I filled a few tanks of high quality gas (Chevron, Amoco). Before, the car was ok performer....after a while, it actually was able to spin the tires with the 1-2 shift! There was a definate change in peformance.

[Sentientbydesign]

About 2/3 of the way through your "article" I started just seeing words and couldn't focus on sentences anymore.

As far as octane determining the amount of energy contained in the fuel, you are incorrect. The octane is simply a rating of the fuel's resistance to combustion. It has no correlation to the amount of energy per unit.

As far as oil change intervals. Again, we all have our different opinions, but that cute number 3,000 or 3,500 is just that a number. It's not magical, it doesn't mean that within 500 miles of that number the lubricating abilities of the oil are going to plummet. It's a sad average made a long time ago when oils were poorly designed (some of us *cough* telcoman! still like using those antiquated oil technologies lol).

Here are a few other things to consider. If I'm not mistaken, the G35 owner's manual says to change the oil ever 3,750 miles.

Secondly, synthetics that are designed for extended change intervals are designed for extended change intervals. Changing extended service oil every 3000 miles is like changing your socks multiple times a day. There may be instances where you really made those socks REALLY dirty, but for the most part they're fine and you're just wasting laundry resources for the Hell of it. I've done enough research to believe that, just like you can't be agnostic if you haven't studied the various religions.

Filling up with low octane gas doesn't "confuse" your ecu. A well cooled engine with near perfect thermal properties could run on gas well under 87 octane and not "confuse" the ecu. The issue here is that low octane gas CAN cause premature detonation thereby causing knock and forcing your ecu to retard timing.

In extreme situations, this can cause severe engine wear. In most cases, the knock sensor realizes you're an A$$hole for putting cheap gas in and the ECU fixes the problem. There's no confusion involved.

Have any of you ever run track? Using cheap gas is like runing "stiff leg bound" 50% of the time. You can do it, but what the hell is going to happen to your joints from doing that so much?

I personally like Shell. It runs very smoothly in my I30 with over 275k miles on it. The Chevron wasn't "Simply smarter". I got rough results with their high grade stuff.

[tollboothwilley]

At least your lowest fuel octane is 87.

In Utah its at 85 for some reason...and still hella expensive

[redhed]

about the only thing that would truly decrease fuel consumption on the G would be a taller overdrive ratio and/or taller rear axle ratio. the engine runs too many rpms on the interstate cruising...jmo.

[mrsmithGrider]

I agree, back when I first got mine i thought there was something wrong because i was doing 3g rpms at 80mph......deff need another gear

[Jacko3]

Sentientbydesign:

But you are saying the same thing I just said. Lower octane gas will resist combustion far more than higher octane gas. The thermodynamic effect is that you will use or require more energy to overcome that resistance with lower octane gas than if you used higher octane gas. When I speak of "energy", I am talking in thermodynamic terms. Most people have no clue about therrmodynamics or the thermodynamic properties and calculations that go into auto design.

So, in essence, you just rephrased what i have said. I am right, just as you are right about the resistance to combustion. We are both saying the same thing. However, your speak form a mechanical stand point, and I am speaking from a thermodynamic stand point.

As long as the energy levels developed in the cylinders are different from inputted numbers in the ECU, the ECU will work hard to compensate for those effects. The only reason why a G-35 Sedan will have a lower octane rating in the manual than the G-35 Coupe, is because of the thermodynamic proerties of the engines, during design. Just becasue VQ engines are ubiquitously used in all Infiniti cars, does not make every of their thermodynamic properties the same. ECU manufacturer presets, have a lot to do with the interaction of thermodynamic properties of the engine.

The ECU data on the G-35 Coupe are slightly different than the ECU data on the G-35 Sedan eventhough they are both the same engines. Why? They are different becasue the ECU also has to take into account the thermodynamic properties of the two engine designs.

So, we are both saying the same thing. If you evaluate this discussion in terms of systems, energy produced, and workdone, you will agree with both our comments.

and, becasue of the thermodynamic properties of different engines, engines that require high octane gas, are actually best suited for modifications, such as cold air intakes and plenum spacers, as the extra air really produces more energy in the combustion chambers, and thus better MPG.

Give this a thought and I am sure you will agree. When i add parts to my car, I am thinking in terns of stresses, energy, work done, fluid mechanics, and allt he rest. that is why I have been hesitaant about undecrank pulleys, which really do change the fluid mechanics of the car. Slower fluid will produce more acids, which is what the undercrank pulleys do (reduce the speed of turning water pumps, power steering fluids, etc). It is analogous to letting a car sit for days. When you let a car sit for too long, the fluids int he car starts to build acids that deteriorate metals and plasctic fixtures. Thus, a new car that has been driven very little in its life time, is as bad as a car that has been driven 400K. This is why I am opting for the non-underdrive pulleys for my car, when they are available.