What gas type is best for our turbo'd saab's? [Archive] - SaabCentral Forums

: What gas type is best for our turbo'd saab's?

1st February 2010, 07:27 PM
I looked around but I could not find any info on this question. I remember reading a review where they said the 9-5 2.3t only needed reg. gas as for the Aero needed Prem. gas. Is that true or should we just use prem. gas since its turbo'd?

1st February 2010, 07:34 PM
I believe the rule of thumb is that cars with turbos should almost always get higher octane fuel.

The saab manual will say different though.

1st February 2010, 07:42 PM
Thanks...I would rather not spend the extra cash if its not needed if the ECU mapping does not require prem. to run at its peak but being a Audi guy I have always ran prem. in my turbo'd Audi's...

1st February 2010, 08:19 PM
You don't need premium. You will yield more performance with a higher octane fuel, but our ECU's can accommodate lower octane fuels. However, if you think about it, on a 10 gallon fill up, you are only spending about 3 dollars more. So, if you fill up 15 gallons, you'll be spending an extra $4.50 on premium compared to regular. I NEVER use anything below 93 in my Saabs. Burns cleaner therefore I feel better about my car.

1st February 2010, 08:42 PM
Cool and thanks for the info. I just found out that the dealership is throwing in brand new spark plugs from the Saab dealer and installing them for free before my wife leaves with her new Saab, which she picked over the Audi's and Bmw's she drove before.

1st February 2010, 09:48 PM
ALL 9-5's (LPT, HOT, V6t) can run on any fuel you put in them just fine with absolutely no damage to your engine. If you want to get maximum performance (power and efficiency) though you need to run premium. I heard somewhere that the Aero models can lose as much as 30hp when you switch to low octane fuel. It's not easy to switch back and forth either. "Oh I want to drive hard this week and have some fun, I'll put premium in." It doesn't work that way. When going from a high octane to a low octane the engine adjusts very quickly, but it takes a LOOONG time for it to come back to its full advertised power once you start putting good stuff in again. I had a V6 and now an Aero and I have always done 89 in the winter and 91-93 (depends on where I fill up) in the summer. I have not taken the time to do the math but some have reported that they get better MPG's with higher octanes and the better mileage almost negates the extra price per gallon at the pump.

1st February 2010, 09:49 PM
The consensus is you need premium for your car. There are many threads on this topic.

1st February 2010, 09:57 PM
So the vote is in for prem. I thought so but justs wanted to be for sure.

Thanks guys

Paul Campagna
1st February 2010, 10:06 PM
Premium only....

2nd February 2010, 01:28 AM
Shell V-Power is the best IMO for our cars.

2nd February 2010, 01:33 AM
Cheap gas = knock and preignition

Expensive gas = non of that

I use the highest octain that they sell 91 and somtimes 94 but i dont find it very good.

2nd February 2010, 02:48 AM
I go with V-power 93 octane, if for any reason that is not an option then I go with the highest octane top tier fuel with the best detergent pkg. I can find. I know my car will detune to try to protect itself if I run crap fuel, but I don't want that !

2nd February 2010, 01:22 PM
BP is good in a pinch

Chris 9-5
2nd February 2010, 01:25 PM
methane is rubbish :confused:

2nd February 2010, 03:36 PM
Okay, so I’m going to go against the “conventional” wisdom of the forum and probably stir the pot a little. You do not need to run high octane fuel in your Saab 9-5. There, I said it, now let me explain why and dispel a few myths about the “regular” vs “premium” fuel. On to my fun little rant.

Myth #1: “87 Octane fuel leads to more detonation and knock. This will result in early death for your car. Higher Octane fuel will not knock or detonate.” There is some truth to this, but not really much. It’s true that knock and detonation will damage internal engine components if they reach above a threshold limit. HOWEVER, our cars run adaptive spark control, and a knock sensor to monitor knock. What adaptive spark control does is advance the ignition until just a little knock is detected, then backs the ignition off a degree or two. If a lot of knock is detected the ECU can back down boost pressure, and ignition, then throw a CEL. As you can see, if the ECU is pushing the ignition further and further to the ragged edge, premium fuel will knock just as much as regular, that is very little. What premium fuel will do is allow the ignition to run more advanced, which affords a little more horsepower.

Myth #2: “High octane fuel is always better for the engine and produces better performance.” I know I just got done saying that with high octane fuel you get more horsepower, but that comes with a few caveats. First, THERE IS MORE TO FUEL THAN AN OCTANE NUMBER. Fuel is a complex mix of several hydrocarbons and additives, and a multitude of combinations can result in the same octane number, but the BTU content (energy content of the fuel) will be vastly different. For example, many fuel producers use ethanol to boost the octane number. Why? Ethanol is pretty plentiful (atleast in the Midwest) and has a relatively high octane number (E100 has an octane number of 106RON). As a matter of fact, E10 automatically is 2 points higher. Ethanol, however, contains only 76,100 BTU/gallon vs Gasoline’s 114,100 BTUs/gallon. This vast difference means that high ethanol content fuels require more fuel to extract the same energy. (You can expect significantly lower MPGs with oxygenated fuels than with non-oxy fuels.) Some of this can be made up for with higher effective compression ratios or effective volumetric efficiency (running higher boost), but not all of it. Where your fuel comes from makes a big difference. The mix matters. Not all premiums are created equal.

There is another problem with ethanol. It loves water. Ethanol, as an alcohol, has a strong affinity for water. This is okay in small amounts, there is virtually no such thing as gas line freeze anymore because the water is in solution. But water doesn’t burn. The longer the fuel sat in the tank underground before you pumped it into your tank, the more water it is likely to contain. The more water in your fuel, the less energy there is in your fuel. I can tell you from experience, premium turns over much slower than regular.

In my experience and education, the biggest difference there is between 87 Octane and 93 Octane is the detergents. My recommendation? If you run a fuel system cleaner through your system on a regular basis, and you haven’t modified your ECU for max boost, or disabled the knock/preignition detection, and you don’t need the ABSOLUTE RAGGED EDGE Max Horsepower ALL THE TIME, then you can certainly run 87 Octane, provided you do not buy it from a “discount” gas place. I recommend BP myself, and I avoid SA like the plague (high alcohol content). The best mileage you can get is Non-oxygenated premium, which is illegal in MN except in special cases.

Also, Octane boosters in the bottle = WORTHLESS. When it says "raises octane 5 points" thats a whopping .5 on the octane scale, so 87 octane becomes 87.5, not 92.

Now to justify this ramble, where did all this come from? I’m an ASE Master Technician (10 years) and I hold a Bachelors of Science in Automotive Engineering Tech from probably one of the leading school for ethanol study in the US. Sorry, this is one of my pet peeves.

Oh, and Methane is terrible for BTU content (56,800BTU/Gallon) but great for Octane number, if you can run 25:1 compression.

2nd February 2010, 03:55 PM
x2 ^

(what he said)

2nd February 2010, 04:33 PM
Early in my SAAB ownership, the car (2000 Aero) developed engine problems, the check-engine light came on and I ran it to the dealer. I still had a warranty at the time, about 45k miles on the odo.

The dealer's head mechanic showed me that a couple of valves had become caked up with unburnt gas that turned to tar. He showed me the valves so I could see what he was talking about. He said that was because I was driving the car with lower octane gas. He said I should only use premium; that was what the car was designed to run on. He also explained that using premium fuel was really no higher investment because the car would get better MPG's using premium, so the delta in savings was not there.

Anyway, ever since, no more low-quality gas for me. And I haven't had any more valve jobs, 100k miles later.

Just my 2-cents...

2nd February 2010, 04:38 PM
Low octane <> Low quality

2nd February 2010, 04:54 PM
Okay, There is a big difference between Low Octane and Low Quality. Yes, Low QUALITY fuel will leave deposits on your valves, yes, Low QUALITY fuel will cause additional knock and preignition, yes low QUALITY fuel will plug your filters and injectors, yes Low QUALITY fuel will contain a high amount of water, yes low QUALITY fuel is bad for your Saab.


It's not about the number. Besides, are we talking RON, MON or Average?

If we really want higher OCTANE, lets all resolve to upgrade our ECUs to run E85, with an octane of approximately 105 ((R+M)/2 method). In that case we can anticipate a decrease in mileage of upto 33%. This would of course be decreased by the adaptive spark control, and if we used a tuned map could be as low as probably 10%, but if we don't run greater boost, and more advanced ignition, we can anticipate both a drop in mileage and in HP.

Paul Campagna
2nd February 2010, 10:53 PM
I couldn't get through the long post. People can put whatever gas they want in their car, but there are stickers on two of my cars that say use high octane, and (surprise) they run better and get better gas mileage running Higher octane.

The turbos run better on higher octane... If your car is a turbo, then if you want to get the best performance and longevity out of your car, run premium. If you don't care how your car runs then buy the lower octane.