89 octane and expensive premium gas ?

[JHZR2]

Hi,

I have a 2004 saab. It is designed to take US 90 octane gasoline. That is what its optimized for. Any higher, and it is commonly known that a sulfur odor will come from the exhaust/cat more often than otherwise, and it is also known that there just will be more HC going through the system, as spark cant advance enough to use it.

I have been running 93 out of simplicity, but I would just assume not pay for the higher octane that I cannot make use of. 89 from the pump kind of sucks because they dont charge you proportionally compared to the ratio of 87/93 that they give you. I typically buy gas in N.J. where it is cheapest. They pump the gas for you, so I cant mix 87/93 for myself typically, to get a few penny cost savings. So I think I'll just be buying 89 octane (and using FP). I am curious if typically at the stations where there is a supposedly top-notch premium fuel, like v-power or amoco ultimate, (which has its own transportation pipeline), if the 89 is typically a mix of the super wonderful premium and the 87, or if stations actually typically do something else, like keep a seperate tank and buy from the terminal a pre-mix as an inferior 89 octane fuel, etc. to save money.

It would be great to buy 89 at amoco, and be getting a relatively high percentage of their ultimate 93 in there, or similarly, to buy shell 89 and get a good percentage of their v-power adds in the gas. Unfortunately I have a sinking feeling this isnt so. Do most gas stations blend from the 87/93 tanks on-site, or do most but a seperate 89 octane tank? If they do mix, do they typically mix in the 'good stuff' 93 octane?

Thanks,

JMH

 

[1maniac]

Yep. I'm in the same boat with my BMW. With gas prices on the rise I dropped from Amoco/BP (BP sells Amoco gasoline here in PA) 93 octane to the 89 octane and can't tell a difference. However if I run any 87 octane it's poor performance from the BMW. Some other station's 89 octane is garbage too. I always try to get Amoco as its top notch stuff!

 

[dB]

quote:

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Originally posted by 1maniac:
Yep. I'm in the same boat with my BMW. With gas prices on the rise I dropped from Amoco/BP (BP sells Amoco gasoline here in PA) 93 octane to the 89 octane and can't tell a difference. However if I run any 87 octane it's poor performance from the BMW. Some other station's 89 octane is garbage too. I always try to get Amoco as its top notch stuff!

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I don't understand the reasoning behind dropping grades when the prices go higher. The delta between grades remain the same, so you are actually getting a better deal on premium at the higher prices. You're paying $1.00 extra for 10 gallons between 89 and 93 whether the price is $1.50 or $2 per gallon. ??????????????

 

[JHZR2]

this is true, the price relative to the total outlay for fuel is less.

My issue is that my car is designed to use 90 octane fuel. It is well-known that anything higher contributes to a rotten-egg smell from the cat, and that the spark timing cannot be advanced any further, nor boost pressure increased to use the higher octane. So, why pay for it, only to have it contribute to higher HC levels in my exhaust? The best thing to do is buy the lowest octane your car is specced for, or that it can run on without pinging. My car will take 87, but it will retard timing, and power will drop. I don't want that either.

If 91 was available, as it is out west, I wouldnt care. But 93, which is commonly available here, seems a bit too high, and it seems that long-term it may contribute to extra carbon, shorter cat life, etc.

So, mainly out of curiosity, I was wondering if the stations blend in their high quality premium/ultimate gases to get 89, or if they use a seperate 93 octane (with a cheaper gas than say, amoco ultimate, or less additive content than v-power) tank to blend with the 87 to get 90.

89 is a ripoff by average price, but where I get my gas in NJ, they pump it, so I cant make my own mix by purchasing two seperate loads of gas, half 87 and half 93. So I might as well save the few pennies and give my car closer to what its specced for, rather than sending all the unburned HCs out.

Or am I just being silly?

JMH

 

[dB]

I'm not sure what to tell you, other than I'm not sure running 93 all the time will have detrimental effects on the car. You could try always filling up at half tank one time with 93 and the other with 87, but that's an awful lot of stops. I run V-power 93 in my old Audi, but the cat's gutted. It doesn't ping near as much as on 87, and I've been consistently getting 2mpg more on this V-power versus old Shell premium. The exhaust does smell, though.

 

[Gary Allan]

quote:

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So, mainly out of curiosity, I was wondering if the stations blend in their high quality premium/ultimate gases to get 89, or if they use a seperate 93 octane (with a cheaper gas than say, amoco ultimate, or less additive content than v-power) tank to blend with the 87 to get 90.

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The only stations that blend 87 and premium at the station are Sunoco service stations. They typically have three tanks (as all stations typically do). Two are for the cheap ...one for the 94. They then have typically one pump per island dedicated to the cheap (in former years dedicated to 94) .and two sets of the blending pumps.


I agree that it's cheaper mathmatically for the average octane to buy a 50/50 ratio of 93/87 ...get 90 octane and pay less then you do for 89 octane. The current "spread" here is $0.14-$0.18 between the two ..while the 89 (plus) is always higher then the mean ..which, mathmatically, it should be lower than the mean. This assumes that the octane scale is linear ..which without further evidence ..most of us assume is true.

In your case, given that NJ has no self serve, why don't you just alternate your purchase of 93 and 87 to balance out your tank? You will run +/- the octane rating that you desire ...but will be getting what you pay for in a more genuine manner. Which I believe is the hair that we're splitting here.

 

[GT Mike]

Nearly all the stations in WI only have 2 tanks. One for regular 87, and one for premium 93. The midgrade 89 is a mixture of the two. You can even feel it when you're pumping midgrade, it pumps slower and you can hear something inside the pump click once in a while.

I'm pretty sure even the BP and Shell stations have only 2 tanks. In fact, I know for a fact one Shell station only has 2. I was working next door to it while it was being built, and asked that exact question. The owner told me that the midgrade is a blend of regular and premium, and it's done right at the pump.

 

[Gary Allan]

Maybe they do blend them (and charge a good premium for doing it)...but there ain't no stations out there with only two tanks. They tend to have two regular and one premium ..just like Sunoco.

Funny how those in IL get PLUS for less than regular due to the ethanol in it. How do they do that out of two tanks?? three tanks and three tanks

Just the facts, man ...just the facts....

IN FACT ..if the station has been in existance since the 70s ...they've all had three tanks since they carried leaded reg and prem ..AND unleaded. This format hasn't changed even if the content of the tanks has.

[ October 02, 2004, 11:50 PM: Message edited by: Gary Allan ]

 

[Gary Allan]

For those who believe in the blend at the pump theory, I offer this thread. by Fuletankerman

quote:

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There are a couple of different octanes out there for what can be called "premium" gasoline. Read the pump. If it's 92, that ain't bad. 93 is better. If it's 91 I'd definitely pass. The lower octane premiums are simply cut a bit with regular unleaded. That's also where "midgrade" or "plus" gasoline comes from; it's mixed as it goes on the tanker truck--35 percent premium and 65 percent regular in most cases.

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[JHZR2]

I don't know about passing on the 91 octane. My saab only gets timing improvement/power improvement up to 90 octane. Beyone that, the engine does not advance any more, so there is no effect; anything past 90 is wasting.

That said, if one place is charging the same for their premium 91 as another is charging for premium 93, Id pass on the 91 too.

JMH

 

[mechtech]

Fuel Tanker Man stated from experience that mid grade 89 is 65% 87, and 35% 91. So, 50/50 would be 90 or so octane.

 

[JHZR2]

In NJ premium is 93, so 50/50 regular/premium would be 90 octane. Problem is (but I cant complain because gas is served here and is cheaperr than any of the neighboring states) that they dont like to mix. Now, maybe thats laziness on my part, as Im the customer and could ask for it. Fair enough... I could also go to two stations and do a mix, OK, good point.

But in reality my question was if 89 was a pre-mixed 89 octane, done at the terminal, or typically mixed at the station. The reason I asked this is because if I buy shell, amoco, etc., its nice to know that if I was to buy 89 octane, that I was getting ~50% of the fuel with the strong v-power additives, or with the top-notch amoco crystal-clear ultimate gas.

I think my question has been answered by this excellent thread, and I thank everyone for their replies

JMH

 

[seotaji]

You should really consider purchasing a chip to allow your vehicle the ability to advance the timing to higher levels when appropriate. You will always have to use premium though.