# Gas Octane vs. Performance.



## RedwinGV (May 11, 2014)

Ok, let's can the comments about "if you can afford and Audi" and the like out of the way...

With gas prices plunging, has anyone tried using a mid-grade gas vs premium gas? I would think the computers would adjust the timing so in the end, some power would be lost, but how much MPG, if any would result?

Looking at the numbers, premium fuel costs over 15% more than regular and almost 8% more than mid. Yeah, one could use the argument that using a lower premium fuel these days makes less sense with gas prices being lower, but on a percentage basis, the numbers go the other way. I guess it's too much to expect the price diff from the grades to be reduced... not that long ago it was a dime a gallon difference; $0.10 for mid and $0.20 for premium. Today it's 15 and 30. 

So feel free to flame, but I'd rather hear some comments about what performance is sacrificed with the lower octane.... and other issues if known as well.

TIA


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## tagsvags (Nov 25, 2005)

Like you said if you can afford an Audi you should be able to afford the correct fuel. (93 octane)
I will use premium gasoline in my 1.8T as my butt dyno. requires it.
Just wonder why VW is saying use rot gut regular in the same engine in there Golf and Jetta cars.


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## ColoradoA3 (Nov 13, 2014)

I'd rather pay for premium because that's what the car requires. It's not about getting the most performance, it's about fuel igniting at the correct time / temperature. The (turbocharged) engine in the A3 requires premium, run premium.

I haven't actually looked at the price of gas since hurricane Katrina made the prices jump to insane heights. What's the difference? it's always going to change up or down. The ease of not giving a **** takes one less worry out of life.

Unfortunately, your turbo charged 2.0T engine requires premium fuel because that's what it's built to use. Buy premium


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## RedwinGV (May 11, 2014)

ColoradoA3 said:


> I'd rather pay for premium because that's what the car requires. It's not about getting the most performance, it's about fuel igniting at the correct time / temperature. The (turbocharged) engine in the A3 requires premium, run premium.
> 
> *I haven't actually looked at the price of gas since hurricane Katrina made the prices jump to insane heights. * What's the difference? it's always going to change up or down. The ease of not giving a **** takes one less worry out of life.
> 
> Unfortunately, your turbo charged 2.0T engine requires premium fuel because that's what *it's built to use*. Buy premium


FWIW, they area about cut in half... from over $4/gallon to $2/gallon.

I'm too lazy to check, but will do so, but is premium *required*? If it's not, then it's also built to use lower octane fuel too. But true, some engines, for whatever reason, are stated that they should only use premium.

I know my MDX and an EX35 *recommend* premium, but it isn't required. The manuals indicated that some loss of performance could result if one uses lower octane fuel.
With computers controlling the timing these days, it is very likely that higher premium fuel is recommended instead of being required. As noted above, the VW uses reg gas in more or less the same engine.

And I am using premium, but I also used mid with my Infiniti EX 35 and had no issues.. ever. I did loose a bit of acceleration, but one could hardly notice. Since I enjoy driving my A3 with it's pep, I doubt I'll drop to the lower octane fuel, but I am curious as to what would be the results if one did so. I am also burning premium in my MDX, but may be changing to mid. I did it before, but the price difference barely justified the switch... I lost about as much MPG as the fuel saving. With gas so low, the equation has different results.

And Gas has some emotion with a lot of people. I do think premium fuel generally does have some additives that would help the engine keep 'cleaner' as well as the higher octane. That being said, some are also locked into a brand. My frugal side of me isn't, though maybe irrationally, if price were no object, I'd likely be using another brand than what I currently use. Yup, I'm weird that way.


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## gamegenie (Aug 24, 2014)

Too much of a gamble to start filling your premium luxury car with gasoline not recommended. 
It's not like the A3/S3 tanks are huge, they are very small and they fill up very quickly. I fueled up this past monday from empty and only spent $27.95 , and I believe Premium at BP was $2.34 , using the Members discount card I spent $2.24. Sure Plus, and Regular was cheaper but should I even car. I'm already paying far more cheaper prices for gas coupled with the smaller tank than I did a year ago in my Sonata. 

OP, do you top off your A3 when fueling to try get every ounce worth of low cost gas?


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## slo_s3 (Oct 15, 2014)

It's not "required" but recommended. It's not like if you put regular in your car won't start or something lol. But as others have said, your car will run better with it.


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## RedwinGV (May 11, 2014)

gamegenie said:


> Too much of a gamble to start filling your premium luxury car with gasoline not recommended.
> It's not like the A3/S3 tanks are huge, they are very small and they fill up very quickly. I fueled up this past monday from empty and only spent $27.95 , and I believe Premium at BP was $2.34 , using the Members discount card I spent $2.24. Sure Plus, and Regular was cheaper but should I even car. I'm already paying far more cheaper prices for gas coupled with the smaller tank than I did a year ago in my Sonata.
> 
> *OP, do you top off your A3 when fueling to try get every ounce worth of low cost gas?*


Nope, one click is it. 

But I have to ask you, what difference does the size of the tank make? It's not the number of fill ups, but the number of gallons one uses.

As for premium luxury, uh there are a number on non-luxury cars that use premium. There are also some luxury cars that don't use premium. It's the engine, not the car, that directs which gas to use.

So thanks for the comments, but it looks like no one here has experimented using non-premium fuel.


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## RedwinGV (May 11, 2014)

slo_s3 said:


> It's not "required" but recommended. It's not like if you put regular in your car won't start or something lol. But as others have said, *your car will run better with it*.


It may run better in many people's eyes.. those that like acceleration. But if one is trying for a lower cost per mile as being better, that *may not* be the case. And there is some point to this...why do people purchase a diesel option? It doesn't have the performance of a turbo 2.0? And for that matter why do some purchase the smaller engine?

So having a discussion on which fuel to use has some merit in my eyes.... especially if doing so won't harm the engine.


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## sevenVT (Aug 18, 2004)

RedwinGV said:


> It may run better in many people's eyes.. those that like acceleration. But if one is trying for a lower cost per mile as being better, that *may not* be the case. And there is some point to this...why do people purchase a diesel option? It doesn't have the performance of a turbo 2.0? And for that matter why do some purchase the smaller engine?
> 
> So having a discussion on which fuel to use has some merit in my eyes.... especially if doing so won't harm the engine.


You are making many assumptions all in an effort to save a couple dollars on a years worth of gas, with no data to support that going cheaper gas would actually result in a more efficient use of your dollar. They recommend high octane, you want to run low octane. Buy a car that recommends low octane. Stop trying to game the car you bought. 

If you really want to play with your money, you can be our guinea pig and log a year on 89 and a year on 93 and keep track of MPG/acceleration/timing etc in a controlled environment and you can answer your own questions for all of us. 

It's not going to be a simple answer of "Oh the Germans want 93 oct to make up their 0-60 times."

To me it sounds like you are trying to ask permission to use cheapo gas. Permission granted, do what you want to it. It's already been said, that timing is affected by how the gas is combusted, if you get pinging and timing issues, you can lead to long term damage to your engine. If you get no pinging, maybe not. 

I'm sure since you can afford the Audi, you can afford to play games with your engine to the cost savings of maybe a couple thousand dollars over its life in gas, while perhaps ruining valves that costs thousands to fix.

The recommended gas is 93.


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## slo_s3 (Oct 15, 2014)

RedwinGV said:


> It may run better in many people's eyes.. those that like acceleration. But if one is trying for a lower cost per mile as being better, that *may not* be the case. And there is some point to this...why do people purchase a diesel option? It doesn't have the performance of a turbo 2.0? And for that matter why do some purchase the smaller engine?
> 
> So having a discussion on which fuel to use has some merit in my eyes.... especially if doing so won't harm the engine.


not for nothing, but if you're so concerned about squeezing as much mpg out of your car as possible, why didn't you buy a diesel? or a hybrid? As stated, running lower quality fuel won't harm your engine, it just will not give you the maximum performance that some look for. The only gas that's going to harm your engine is gas that has water in it or if you put diesel fuel in your car


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## ERTW (Jan 17, 2000)

RedwinGV said:


> Ok, let's can the comments about "if you can afford and Audi" and the like out of the way...
> 
> With gas prices plunging, has anyone tried using a mid-grade gas vs premium gas? I would think the computers would adjust the timing so in the end, some power would be lost, but how much MPG, if any would result?
> 
> ...


First, try to not use terms of premium, mid or low grade as this changes depending where you live in North America.

In Canada where I live, we only have access to 87, 89, and 91 octane. Depending where you are in the country you may see 93 or 94 octane. The main reason for the lower octane fuel here is based on our elevation, typical weather/ temperature. The fuel is typically blended for seasonal weather as well.

I have owned a number of turbo cars with aftermarket programming and all function fine on the 91. Would I buy 93 if it were available, of course yes I would, but I would also make sure I run a map that is set for the increased octane and keep a 91 map just in case.

Depending on where you live you may have no adverse effects from running 91 octane, but the reason for the premium requirement is to ensure optimal operation of the engine. If your city offers 93 octane then you may just live in a warmer, lower elevation location and advice would be to fill with the 93.

On the cost side, when I travel to the US, I always feel like the fuel is always on sale. Typical fuel cost here is around $5.20/ Gallon but with the latest drops is has been $3.62/ gallon which is nice but in the whole scheme of things it doesn't matter a whole lot when you factor the cost of the car, maintenance, insurance.


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## KingoftheWok (Jul 30, 2014)

FWIW, I only use Shell 91 mainly because it is 0% ethanol. I'm located in Canada as well. I have heard there maybe long term issues with using gas that uses ethanol as a filler which can dry out the internals over time. Whether or not that is true, I don't know but I love my car and treat it with care. Spending a few bucks more for peace of mind is worth it in my opinion.


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## misaka (Feb 8, 2013)

Odd, Do your cars show 93 octane on the gas cap/door? Mine shows 91 octane recommended. I always put 93 since in NY we only get 87/89/93.

Also I know the engine can pull timing to use lower grade fuel, but how do the cars know to adjust? I'm pretty sure there is no octane sensor on the A3. It probably senses predetonation/knocking/vibrations then adjust accordingly. If someone knows I'd love to hear more about this aspect. ie how does an engine know to switch back to different timing after you've put in premium gas afterwards?

There are some turbos tune for 87 octane. The new Golf 1.8T in the US appears to recommend 87 octane, and specs similarly to the Audi 1.8t, so I'm not sure if it's running just a different map or Audi doesn't make a 87 octane sticker for the gas cap.


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## Tony_S3 (Sep 9, 2014)

I always use whatever is recommended. Knew that coming in. Out of ignorance I stay away from stations that have "Ethanol Added" on the pumps.


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## ColoradoA3 (Nov 13, 2014)

To be objective:

If higher octane will ignite at the correct time / temp (the way the engineers intended), it will result in the most efficient use, correct?

So if someone were to run 85 or 87 octane, and get slightly worse performance, would they use more gas? I'm genuinely interested in the answer. The easy way to test would be to fill up once with both and measure your MPG based on the receipts. Then estimate cost based on those prices (make sure to note the price for reg and premium both times)



I think I'll sift through my owners manual to see if it uses the word required or recommended. Either way I'm still using premium.

Here's an interesting article. It specifically points out who's required and who's only recommended. All the audi's seem to make the required list. I'm sure the ECU accounts for lower octane fuel enough to not destroy the car, but I wonder WHY edmunds put them on the list


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## RedwinGV (May 11, 2014)

ColoradoA3 said:


> To be objective:
> 
> *If higher octane will ignite at the correct time / temp (the way the engineers intended), it will result in the most efficient use, correct?*
> 
> ...


From an MPG and acceleration, using the higher octane will almost assuredly be better with the higher octane. I've seen this in my other vehicles. However, one does have to pay more dollars to purchase the higher octane fuel.

And to some, I'm not asking permission to use lower octane fuel. And to others, I like the acceleration and that is why I got this engine configuration. That being said, using a lower octane of gas is not a huge mistake. I mean, having a lead foot will very probably result in more negative effects on the engine than using a lower octane fuel. So save your comments about ripping me for trying to save some money on gas to only use it for potential engine repairs in future years. I don't know if that is the case and honestly that is the information I am asking for. And yes, I'm still using premium and likely will continue to do so, but I still see this as a relevant issue.

Hell, let me throw this at those doubters... If one isn't using the best high priced tire on the car, are they being fools? I mean, if you're not using a great tire, you can't get the best traction and control that the vehicle is capable of. FWIW, I use tires with great traction and stopping distances as I find it worth the money for me.


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## sevenVT (Aug 18, 2004)

RedwinGV said:


> Hell, let me throw this at those doubters... If one isn't using the best high priced tire on the car, are they being fools? I mean, if you're not using a great tire, you can't get the best traction and control that the vehicle is capable of. FWIW, I use tires with great traction and stopping distances as I find it worth the money for me.


Arguably, if you aren't doing the best you can for your car... you aren't doing the best for your car. Going against dealer recommendations, or modifying contrary to warranty or insurance requirements means that things you have paid for you are rolling the dice on for undisclosed or unquantifiable gain/loss.

Its like asking if you should remove your trunk lid to gain more MPG due to weight loss, are you going to also ask if your coef is less or more, or if the aerodynamics of the air now circulating in your trunk is going to out weight the benefits of the trunk lid being gone? Has anyone done this before? Probably... is it recommended? No. 

I guarantee if you don't drive your car you'll spend less in gas. Also if you don't drive your car with 87 octane in it, you are far less likely to have pinging and valve issues far into the future.

Short of that, its time to take your own car into your own hands. Anecdotes are all you are going to get here.


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## misaka (Feb 8, 2013)

RedwinGV said:


> Hell, let me throw this at those doubters... If one isn't using the best high priced tire on the car, are they being fools? I mean, if you're not using a great tire, you can't get the best traction and control that the vehicle is capable of. FWIW, I use tires with great traction and stopping distances as I find it worth the money for me.


Whether you choose to use premium or not, it's your car. No one can probably give you the peace of mind you are looking for, because everything will just be anecdotes, not hard data.

Your analogy here is a bit off though. It would be more along the lines of, the A3 comes with H speed rated tires which are rated up to 130mph. These are the recommended specs for this car. Granted 99% or possibly more of the time you will not be driving at 129mph. You could get a lower speed rated version of the same tire like a S rated tire. Which honestly who would normally exceed 112mph? But would your chance of failure be higher if you were pushing it? Maybe? It's not that you'd probably notice, but it wouldn't be according the the recommended guidelines, which would allow the manufacturer to void your warranty should it cause any issues etc. 

That being said, do as you want lol, it's your car. I'm ok with the mild difference premium costs. Heck they could charge me 2x the amount and I still will do it. I have a Mazda 3 which takes regular gas just fine, and I drive that if I feel like I need to be economical.


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## RedwinGV (May 11, 2014)

Thanks for the comments. I expected the comments that others have or may share on this thread would be anecdotal. And others that make aftermarket changes also share anecdotal comments on this site too, yet they do add to the site. I was just curious if anyone explored this. I guess raising a question that may lower operating costs is out of bounds for a few people. I should just move on to another topic. See ya on the board.


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## RedwinGV (May 11, 2014)

ColoradoA3 said:


> To be objective:
> 
> If higher octane will ignite at the correct time / temp (the way the engineers intended), it will result in the most efficient use, correct?
> 
> ...


Hey, thanks for the link. Interesting that it does show that the A3 (along with the TT) is one of those recommended and not required ones. As I think I mentioned above, I did this with my previous and current vehicles and found that it wasn't worth much savings on my MDX but did give me some savings with my EX35. With the price of gas being so much lower these days, the percent differences between the octane grades is much larger... like 15% if one drops to the lowest rating and almost 8% if one drops to that mid octane rating fuel. So the savings vs MPG drop is larger. And to quote the linked article:

*For those driving "recommended premium" cars, however, it's just a matter of driving moderately and avoiding acceleration with a wide-open throttle. Do that and you might never feel the difference between using premium and regular grade gasoline: and neither will your car*.

So this is why I brought this up.... curious if anyone else tried to run the lower octane and share some experiences.


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## barho (Jun 16, 2014)

Recommended in the A3 is actually 91.


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## Pommerening (Jan 17, 2014)

I filled up my 2.0T A3 with 89 octane, ethanol free from Fleet Farm this fall. I really felt like my car ran like a dog on it. It ran similar to how my car runs now with 91 octane but in below zero weather. Sluggish, and worse mpg. I added 93 octane twice to mix the 89 up to 91. Maybe it was placebo effect or just bad gas, but I only put in 91 octane now. I filled up with Shell 91 yesterday and it was $.60 more than reg, so tell yourself from now on that your getting a deal buying premium only $.30 more.


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