Good Morning - I am proud, new owner of a 2009 A3... and very happy with it so far! One question I had was regarding the use of regular gasoline with the 2009 A3. When the dealer was going over the features, he mentioned that the newer models can use either premium OR regular - and that premium was NOT required. Obviously, more of a selling point with respect to recent gasolines prices.

1.) I'm aware that "performance may suffer", but will I cause irrevocable engine damage by using regular? Will I reduce the lifecycle of the powertrain?

2.) What differences exist that allow the newer models to use regular, while the older models cannot? (I was under the impression its the same engine as the 06, 07, 08 models).

3.) If I choose to use regular - should I wait until the engine has been burned-in a bit? (I'm only on mile 124).

Thanks in advance!

- Salty

 

nice ride,keep it simple.regular!does the job.

 

I also have an '09 A3. It's my understanding that performance and MPG will suffer with regular. So the perceived savings is minimal because of the reduced MPG with regular gas. Plus the car is more fun to drive with the higher octane fuel. And if you should decide to chip the car only premium fuel can be used. So spend the extra couple of bucks per tank and enjoy.

 

None. What you experienced is a case BBSF. For the non-acquainted, it means bullshit based selling feature. (the '09 engine is not quite the same as 06-08 models, but the lack of "valvelift" in previous years doesn't mean they don't run on regular; it improves gas mileage though).

 

the two to three miles per gallon you loose in a tank full will offset any savings.

Your are correct, it will not hurt the engine.

 

Dude...awesome on the new car! Thought if you were switching you'd come over to the impractical side and join the TT crowd

Just use premium, especially if you flash the software. But within the range, the ECU will adjust for whatever you choose to put in it. Pics of the new ride?

 

Thanks for all the responses folks! Maybe I'll run my own experiment and see what the MPG difference is

I will try and get some pics up! Overall - VERY happy new owner.

 

I was going back and forth between regular and premium gas. I can't say I noticed any difference in either performance or gas milage. Now I almost always use regular. The New York Times had an article on this a few months ago, basically concluding that regular won't hurt your engine and that if it it performs differently, you can always go back to premium and you will immediately regain the lost performance. The link is: http://www.nytimes.com/2008/08/03/au...0gas%20&st=cse

 

Actually contrary to popular belief you will get better gas mileage with regular gasoline vs. premium or high octane gas.

Fuel's all have a BTU value (British thermal units) which is a measure of how much energy can be extracted from burning or consuming gasoline. Premium gasoline (91 octane) has a lower btu value of 3-5% vs regular gasoline (87 octane). Gasohol (10% blended Ethanol gasoline) is again about 3% lower than premimum (even with higher octane value of 93-94) and is sometimes sold as a super premium. So 87 is highest then 91 then finally 93-94 from a BTU stand point, just to be clear. Many stations sell 87-89-91-93. Only 87-91 are ethanol free 93-94 octane gasolines use 10% ethanol to make up the octane number, but have the lowest BTU value of any gasoline. Ethanol has a btu value 47% lower than gasoline but a high Octane value of 129. So you can see a trend here. High octane fuels have low BTU values.

Diesel has a BTU value significantly higher than regular gasoline around 11%. So not only are diesel engines more economical the fuel they burn has 11% more energy stored in it than regular gasoline does. The Octane value for Diesel is 25 fyi... but the octane value of diesel considering they run on compression is irrelevant. Cetane Number is more important for diesel but I wont elaborate on that as it's not really relevant to this discussion.

So what the point of all that information? You will get better MPG on Regular gasoline (all else being equal) than you will on Premium 91 octane or Super Premium 93-94 octane gasolines that are blended with Ethanol. Any gasoline blended with ethanol (Gasohol) will have a good octane value but a really poor BTU value as Ethanol has such a poor BTU rating.

Lets talk about Octane and what it's doing for you. Octane really matters when you are at wide open throttle. The ecu in your car has two operating methods. Open loop and closed loop. When you are in closed loop that means the ecu is looking at the sensor values and continually changing ignition timing to provide the best gas mileage possible. Closed loop will ignore the O2 sensors and run on a fixed timing map that is fixed almost ignoring all the sensor values. So in closed loop at partial throttle lets say at 50mph your car is making bout 25hp to keep the car moving at that speed. Timing is advanced really far and the relative stress/heat on the engine is very low. During this type of driving your octane value is basically irrelevant. A gasolines octane value is a measure of its resistance to knock or pre-ignition due to high heat or pressure in the cylinders. You will not have a situation of knock or pre-ignition during part throttle because the load on the engine is so low. So while driving on the highway and easily around town you can run almost water in the engine (if it was combustible) and it would be fine. So the BTU value of the fuel is the most important, what will give you the best gas mileage is the fuel with the most energy.

During open loop driving (wide open throttle) the motor is under much more load. Obviously fuel efficiency is thrown out the window here for maximum power and acceleration. The more fuel you can burn the more power you make.. Horsepower comes from burning gasoline. That's why an engine has a turbocharger so you can force more air in it therefor burning more fuel, thus making more power. So octane here is paramount as any knock or pre-ignition can potentially damage the engine (burn holes in pistons, bend rods, melt valves etc.. lots of fun stuff) and cost a lot of money in repairs. So in a racing application where MPG are irrelevant the highest octane fuel is used. That's what "alcohol" funny cars refers to is alcohol or a really high Octane fuel. They must burn twice as much of it to get the same power (low BTU value) vs. gasoline but because its so stable with 140+ octane numbers and burns so cool. Even though you need to burn twice as much it will make more HP than gasoline will. A 4000hp 4 second dragster has so much fuel injected into the cylinders they are near hydro-lock during the combustion cycle. They could make the same power with half the amount of gasoline (in theory) because of BTU value and in doing so would double it's MPG. Obviously the low octane value of gasoline (even racing gas) and instability of gasoline vs. alcohol would make that impossible.

Sorry for the long post, I'm bored and thought I would ramble for a bit.

 

so ur saying high-octane, ethanol-free is what we should be lookin for!!!