Hi Everybody,

I'm new here--bought a '03 Desert Platinum Premium Package Auto in Feb from the local Infiniti dealer with 6600 miles on it. I'm loving it!

My gasoline question is I'd like to know why using 87 is a no-no as I've been doing this with absolutely no problem. The car runs beautifully and any difference with premium 91 (best we got in San Diego) is undetectable. There is no pinging at all that I can ascertain. The reason I'm being a cheapskate with the 87 is that in San Diego a tank of regular unleaded is already running about $47.00+.

Thanks and I'm enjoying reading the forum.

 

The G holds 20 gallons.
Premium gas normally costs .20 more a gallon than regular.
So every time you fill up it costs you $4.00 more to use premium. If you fill up once every two weeks(normal 15k yr) then are you saving $104 per year.
If you own a G you probably spend more than this on a nice dinner.

Is it really worth $100 a year to put your car in risk? What if your car is pinging and you can't hear it?

So can you go without premium? Sure but you could probably go without changing your oil too, and you would save about the same about of money.

 

When using 87 octane your run more of a risk of pre detonation of the fuel. the car's ECU will retard the timing to compensate which will give you a bit less perfomance. Octane raises the tempature point in which the fuel ignites. If your car runs fine on 87 and you don't hear too much pinging then you will be okay. I have maybe run one of two tankfulls of 91. Most of the time I use 87 and like you I don't have any problems with it.

With that said, your not really saving that much cash on fill up. Generally 91 is $.20 more a gallon and on a typical 14 gallon fill up thats only $2.80

One thing to consider is the freshness of Gas. Because the prices are high, stations are less likely to sell as much Premium gas as they normally would. this means it's sitting around in their storage tanks longer which allows more of a chance for moisture and other contaminants to mix in.

 

The owner's manual you got should have section requiring what octane to use, just go with that. If it says 87 AKI you're fine. It might have a recommendation for a higher octane and that's exactly what it is, a recommendation, not a requirement. Of course if the requirement is for 91 AKI, then you'd be negligent to constantly use anything less.

 

I have a 2004 and it runs on 87 octane also per owners manual. Truth be told, it runs much better on midgrade. I never saw a difference in performance or mileage between mid grade and premium. I use the midgrade and feel better performance but the MGP is only maybe 1 MPG more than regular. I too got tired of the rising fuel costs and bought one turbo diesel Passat. Now,I have a sale pending on the G .I am getting a second diesel cause 40& MPG sounds awesome to me. You may go faster but I'll be passin ya while yur stopped at the gas pumps!

 

The 5AT sedan you own runs fine on 87 octane. I have parsonally spoken with Pat Goss and other mechanics who all support the fact that premium is not necessary in this car. The only advantage to higher octane might be a 1/10th of a second faster track time and a one or two mile per gallon increase (depending on many other factors). People have bought into the higher octane is better philosophy, so be it. Pay more if you want to. There is no law against throwing money away.

 

Car and driver just have an ariticle on Nov 2001 regarding premium gas. It used BMW M3 as one of the performance vehicle. This may also apply to the G35s.

http://www.caranddriver.com/article....&page_number=1

"Is premium fuel worth the premium price? Can you hurt a high-octane car by running it on the cheaper stuff?"

"The results were more dramatic with the test cars that require premium fuel. The turbocharged Saab's sophisticated Trionic engine-control system dialed the power back 9.8 percent on regular gas, and performance dropped 10.1 percent at the track. Burning regular in our BMW M3 diminished track performance by 6.6 percent, but neither the BMW nor the Saab suffered any drivability problems while burning regular unleaded fuel. Unfortunately, the M3's sophisticated electronics made it impossible to test the car on the dyno (see caption at top).
Our tests confirm that for most cars there is no compelling reason to buy more expensive fuel than the factory recommends, as any performance gain realized will surely be far less than the percentage hike in price. Cheapskates burning regular in cars designed to run on premium fuel can expect to trim performance by about the same percent they save at the pump. If the car is sufficiently new and sophisticated, it may not suffer any ill effects, but all such skinflints should be ready to switch back to premium at the first sign of knock or other drivability woes. And finally, if a car calibrated for regular fuel begins to knock on anything less than premium or midgrade, owners should invest in a tuneup, emissions-control-system repair, or detergent additives to solve, rather than bandage, the root problem. Class dismissed."
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Great input from everyone, thanks all! There's great arguments from both sides of this issue making it tough to decide what to do. I think I'll need to experiment a bit more with both grades.

 

I look at it this way:

87oct: 14 gallons at 2.10 per gallon = $29.40
Range = 14 gallons at 20mpg = 280 miles

91 oct: 14 gallons at 2.30 per gallon = $32.20
Range = 14 gallons at 23mpg = 322 miles

Benefit of going to 91, 3 mpg increase. so instead of averaging 20 mpg I average 23 mpg. This is a 42 mile difference in range which at the original 20 mpg is 2 gallons of gas at $2.10 per gallon or $4.20. this means that the $2.80 I saved is completely offset and actually costs me more due to the high cost of gas. In duluth we have a place that sells premium(91) at 7 cents more than regular(87), I ALWAYS put premium in the car. Economically, it acutally saves you money, helps your car run better and perform better as well.

 

My quesiton though, is this, how much difference does 100 octane make? We have a place in town that sells 100oct race fuel. I have thought about buying it... but I don't know. I have also thought about trying that octane booster 104+... but havenot heard anythign about it. Does anyone have any input?

 

Not that I don't believe that you get better gas mileage with premium but I don't believe that most people will get better gas mileage. There's just nothing conclusive in this discussion, or any others that I've read, that suggests that using premium grade gas, where it isn't required, leads to higher mileage. (20 mpg on reg to 23 on premium is a 15% boost. That's more than just sizeable, that's enormous. Enough to draw the attention of every automobile manuafacturer that had to answer to CAFE standards.)

 

So even if it is 1.5mpg, that completely washes the difference in cost. So 91 isn't costing you any more money and it isn't saving you any either, but you get the advantage performance benefits.

I haven't ever checked my car, but in an above post, one person realised a 2mpg gain on 91 octane which is very close to 3, which was used because it made for round numbers. In my avalanche2500, while towing, I always go from 8 - 10 or 11 mpg which is like 25 - 30% increase. It offsets the cost so much that it just isn't worth cheaping out on 87. I put 87 in the tank on my last fill on the G because I was in a remote area, so I will calculate mileage and then do another 91 fill and calculate mileage, I will bet that it is at least 2mpg.

 

ashadiow,

I wish you luck. I would like nothing more than getting performance without having to pay for it. (That's what the premium cost offset by higher mileage argument promises.) But your tests aren't controlled and therefore don't offer the promise that a conclusive scientific test would offer. Until such tests are published, I refuse to believe your conclusions.

Cale

 

I know, you are right, I wish I could set up a controlled test, but under "normal driving conditions" which is debatable too and different for each person, I generally see 2-3 mpg in my truck, something I have not yet checked in the G. Nonetheless, I would try it if I were you, run 87 till you are almost completely out, check your mileage, then run 91 till you are almost completely out and see what your mileage is. if it doesn't change it cost you 3 bucks... worthwhile if you ask me. For me, it is also only a $.07 cent difference, so there is no question for me, it is like $1 more so why not.

So is there anyone on here with constant access to a dyno roller? we could run a car completely out of gas, then run 10 gallons of (government certified and tested) 87 till it runs out, then run 10 gallons of (government certified and tested) 91 till it runs out and see what mileage comes out at? it would be an interesting test. I would even donate my G for the test if anyone will fund the dyno time.

 

lamesag35-
As you have seen so far, there are many opinions about this subject. My suggestion to you would be to look it up in the manual. If it is recommended for your vehicle, then it is OK to use. Start with that, then go to higher octanes. You need to decide for yourself if mid grade or premium gas is right for you. Only you will know if you made the right decision. Remember, it is your money, please spend it the way you want. Good luck!