[tristan tumble]

i've read alot of talk about switching fuels for the turbo cars, but im wondering what the owners manual (official policy) says. with gas prices, im considering this as a factor while i look for a car...

also the car im looking at has a performance ECU chip, would that be a cause to use the highest octane fuel?


thanks.

 

[Soon To be Saab Owner]

Your ECU will be able to pull timing and run fine on regular 89-90 gas. Yet, with the peformance ECU I am nearly positive you should be using High Octance, as I am sure it was set up for that gas.

 

[mike saunders]

Most ECU mods require highest octane gas (93 R+M/2 in US)

But...in most cases, making the hardware mods to support the software changes will result in better combustion efficiency and better gas mileage. So, it's essentially a wash.

You'll need to use more expensive gas, but as long as you keep a light right foot, you'll get better mileage with a modded car than without.

 

[Soon To be Saab Owner]

Very true. Although, you could probably get the same mileage with the supporting mods and a stock ECU. Correct? Anyhow, either way you will get pretty decent mileage...

 

[Irorms]

91 octane all the way;oops:

 

[mike saunders]

Very true. Although, you could probably get the same mileage with the supporting mods and a stock ECU. Correct? Anyhow, either way you will get pretty decent mileage...

Correct...

But that's like buying your wife nice lingerie on your anniversary....then falling asleep.


If you're going start modding, you might as well go all the way.....

 

[Saabohème]

mike saunders quipped:

But that's like buying your wife nice lingerie on your anniversary....then falling asleep.

Even worse is buying her naughty lingerie and then snoozing. Yawn.

 

[SaabScott]

Some food for thought as I came home from Las Vegas a week and a half ago to find gas prices up 30+%! :evil:

Anyway ... I have always used the highest octane I can get (usually Sunoco 94 ... 93 at other stations).
The difference in price between that and the mid grade is only a couple of cents.
When you consider the ecology (higher octane is supposed to burn "cleaner" and leave the engine with fewer deposits) and the economy (more miles per gallon with a lighter foot) and the fact that 2 cents on 60 litres won't make any difference to my wallet, I continue to use the good stuff ...

 

[bkrell]

The policy is different. In the NG, it says premium recommended regular ok. I am told in the 9-3 it just says use 93. I've got 87 in mine right now with the MBC off. I think I am going to put it back on and just limit boost a bit, though. If it's not REALLY hot where you are and youdon't ddrive like a nut, you should be fine.

 

[MrAngry]

I have a 97 900 SE Turbo and have only run 87 - is this bad? I've never had any issues with this... should I be running 89 or 93? Is it bad that I am running 87?

I would love further opinions on this.

Cheers -

 

[bkrell]

Nah, it shouldn't be if your car is in good shape. You just won't be getting the performance benefit of premium which in this car (unlike many others) is very real.

 

[MrAngry]

Cool... I got all worried for a minute and thanks for the quick response!:cheesy:

 

[catman]

I have a 97 900 SE 5-door hatch and the previous owner said he only ever used 87 octane gas. At the time I thought this was "wrong" to do and started using 93. Then recently with the gas hikes I thought about it more and went back to 87. Personally, I cannot tell one lick of difference in performance or gas mileage, so basically I fall back on the thought that higher octane gas is only needed for truly high-performance driving in turbo or very high red-line engines that run hot.

I also started using 87 in my 03 Passat Wagon 1.8T and the mileage has actually gone up about 0.5 mpg, but it has only been 3 tanks and it could be ideal weather conditions of late too. But I "feel" as though the acceleration is slightly better at the lower rpms too and I was not even think about this. Not sure why this would be - but it seems consistent - again, maybe perfect weather is playing a role.

No matter what I see no issues with 87 octane gas. Modern computers in cars can adjust on the fly and should be able to handle any gas.

 

[Palmer1980]

Mine had a 1/4 tank of 87 when I picked it up. It had horrible knock under heavy throttle. Needless to say I took the first exit on the highway and put a full tank of 93 in. No more knocking since. My manual says it can run 87, but that noise was BAD.

 

[bkrell]

Nah, mine doesn't really compare on 87. That's why I hate using it. It depends I guess on how healthy the car is. I have 191,000 miles. It still pings a bit under idle w/ regular but never w/ premium.

If MP or PFS or GenuineSaab sold 93 octane as a mod, they could get a lot of money for it. :lol:

 

[mike saunders]

Personally, I cannot tell one lick of difference in performance or gas mileage, so basically I fall back on the thought that higher octane gas is only needed for truly high-performance driving in turbo or very high red-line engines that run hot.... No matter what I see no issues with 87 octane gas. Modern computers in cars can adjust on the fly and should be able to handle any gas.

Catman, you're definitely right about most computers being able to adjust timing and boost to handle sub-premium gas. There's a wide window of allowable octane and the engine can figure out relatively quickly how to set itself up for best output/best economy. But that window is definitely not as wide in a modded car.

Even in a stock car, you can see why if you try this test: With 87 in the tank, find a long hill and try to accelerate up. If it's a hot day, even better. Make sure the radio and ACC are off so you can hear the slight chattering noise. Notice how the boost tapers off. That's the engine fighting pinging.

Do the same run in similar conditions using 93 octane. You'll definitely notice a difference.....

I think the whole point is that 87 is fine for a stock engine if you're comfortable with making a performance compromise. If you have a modded engine, you should feel less comfortable because there's less of margin for the ECU to play with in terms of setting boost and timing. A modded ECU maximizes performance by pre-setting some of these, based primarily on the upgraded equipment on the car and the presumption of highest octane gas for the region.

 

[Soon To be Saab Owner]

Alright, to end all of this argument.... I have read the manual. It says you CAN use 87, or 93. Yet, it says the perfect setting, the one they designed it for, was 90. This is just what my manual said. Anyhow, I always use 89 as we don't have 90 here, we have 87,89,and91 some places 92. It runs great and gets good mileage with no pinging as far as I can tell. Has anyone else read that part of the manual that can agree? Or is my manual different than everyone else's?

 

[bkrell]

I think that's kinda what most of us have been saying... But if you want performance, the higher, the better. Up to a point, at least.

 

[mike saunders]

Soon To Be, the operative word in the original post is "modded"

Stock car, non-turbo: 87-93 octane (Little benefit to higher octane)
Stock car, turbo, driven conservatively: 87-93 octane (Performance advantage with higher octane)
Stock car, driven vigorously: 90-93 octane (Low octane not recommended)
Modded car: 93 octane (Low octane DEFINITELY not recommended)

 

[catman]

Yes,

Absolutely true that a modded car would inherently be adjusted to push the upper end of the cars limits and higher octane gas is REQUIRED.

Stock cars can handle about anything, but it is true that the condition, age, etc of the car can play a role in the "effects" of lower octane gas. Obviously some older cars burn more oil than others, some run hotter than others. Parts wear differently in each car and certainly some combinations will "illustrate" the difference between octane ratings.

I have not had any severly hot weather since running 87, so it will be impossible for me to test the difference right now. But, as long as the car runs smooth and accelerates reasonably, that is all I need. My car has 123,000 miles and I see no point in pushing its limits other than an occassional highway pass or scramble to get somewhere when running late.

Daily leadfoot driving may show the subtle differences more.