Just purchased a 2014 Q5, 2.0t engine. The dealer told me Audi recommends premium grade gas due to the turbo charge system. This increase in fuel prices seems to negate any savings in increased mileage ratings.

Do most of you use premium? and if not, what results are you getting out of a lower grade fuel.

 

I'm in the same position you are. What I know, for a fact, is that the only difference in high-octane gasoline is that it burns slower, which allows it to be burned at higher compression, which in turn means it can provide more power without pre-ignition.

"Low-test" actually has more power, but the pinging prevents it from being used in high compression engines, which means turbochargers especially.

The engine computer detects pinging and adjusts the engine spark timing to prevent it. In theory it could also fiddle with valve timing but AFAIK that's not possible on these cars, or most cars. So when you use low-test, the timing can only be adjusted "so far" before the engine pings, and then the amount of compression (turbo boost) has to be cut back.

In theory then, high-test allows for maximum use of the turbo and maximum engine power but should make no real difference at lower power, when you are just cruising or being gentle on the throttle.

Which would translate into "the way you drive, determines the gas that will work best for you". Lots of acceleration, lots of load, probably something to be gained in high octane gasoline. Best advice I ever got was from a combustion engineer with a world-class pedigree: Use the lowest octane your car is happy with. If it doesn't ping, doesn't complain, doesn't bog down...Higher octane is a waste of money.

I'm ignoring it until I've got some break-in miles on the car, then I'll be using regular and comparing on a highway mpg run, using the cruise control to make sure I'm comparing apples to apples.

So yes, the turbo controller does do something with high-test, but whether you need it? That's up to you. It shouldn't harm the engine at all, no matter what FUD the dealer throws at you about that. Using a "top tier" high detergent gasoline should make a long-term difference in carbon buildup in the engine, but the occasional tank of "cheap gas" shouldn't cause any problem either.

 

Thanks for the info.....from what I've read, I agree with you.

 

While you're at it, you can probably get away with conventional oil instead of synthetic, because it's cheaper. And to save a few more dollars, you can change the oil every 25K miles. In fact, you should just double the service schedule intervals to save a few more bucks.

Seriously, why would you buy a brand new Audi if a couple bucks at the pump is going to break the bank? Audi recommends higher octane to deal with the high compression turbocharged engine. It really has nothing to do with maximum power/ fuel economy. It's about the longevity of the engine. If you consistently use low grade, you will be causing excess wear and tear on the engine. Even sporadic use to save a few bucks now will probably cost you more in the long run.

 

" It really has nothing to do with maximum power/ fuel economy. It's about the longevity of the engine. "
There you go, FUD. How will gasoline octane grade affect the longevity of the engine? My source is an engineer who literally doesn't need an income because his combustion engineering patent royalties pay so well.
I'm not talking about detergents and additives, just about octane, and octane makes a big difference in price--but none on engine longevity when there is an engine computer able to tune for it. Atmospheric pressure, moisture, and temperature all affect how quickly the fuel charge burns and how much power it generates. Octane is only one of the factors in the equation.

As to using conventional oil...More FUD? Do you really believe you can confuse the issues by citing irrelevant information? It is possible to engineer a quality oil in many ways, and "conventional" versus "synthetic" does not tell you if an oil meets any of the relevant standards for turbine lubrication, for thin-film sheeting, or much of anything else.

Changing oil at 25,000 miles? Might be extreme, but if you want the facts, you spend $25 on an oil analysis once in a while, and find out if your oil really does or doesn't need changing, among other things about your engine health.

Save the FUD and dissembling. There's science behind octane ratings, and everything else in an engine. Of course, most of the public is scared of science. You need to learn Arabic numbers to understand most of it.

 

Obviously, I was exaggerating about the 25K mile oil changes etc, etc... and I was using it to make a point... If it's recommended, why wouldn't you use it? Just to save a few bucks at the pump every time he stops in his brand new Audi? Just seems a little counter intuitive to me.

So, as you put it...

How can this not be causing excess wear and tear on the engine?

 

"How can this not be causing excess wear and tear on the engine? "
When the amount of turbo boost is reduced, there is LESS wear and tear on the engine, as it runs at lower compression. High compression creates higher engine wear. Turbo boost creates engine wear.
When the computer throttles back, there is less strain, less pressure, less wear on the engine. When gasoline engines are used as industrial powerplants, the typical 9:1 or 10:1 compression may be cut back to 6:1, and as a result they run "forever".

The Matrix, The Wizard of Oz, the Audi Dealership...some folks like to hear "there there, dear dear, ignore the man behind the curtain" but personally, I get tired of it. Especially when I keep finding corporate fingers in my pockets, and corporate people telling me they're really only trying to do me a favor, checking for that nasty pocket link. Not picking my pockets at all, no, they'd never do that. There there, dear dear.

Nope. Not for me. Or as the formal and proper business executives used to bluntly say, "Don't **** on my head and tell me its raining."

Audi could have the courage, the simple integrity, to say "Your car will perform better on high octane, if you use regular gas your performance will suffer." Instead they would terrorize owners with vague threats of engine damage. Ask them for specifics as to the damage, and they'll mumble and run.

 

Ahhh, I see you're point... OP, stick it to the man and use the cheapest low octane gas you can find! That will show them!