Used wrong gas - Car OK? (2017 a4)
07-26-2017, 10:25 AM
#1
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Used wrong gas - Car OK? (2017 a4)
Hi Everyone: By accident I filled almost my entire tank with 87 octane. I just finished the tank on mostly a long distance trip. I now have about 2,500 miles on the car. Noticed a little bit lower mpg. But is my engine, etc. going to be OK? Just want to make sure. Thanks everyone! -David
07-26-2017, 10:30 AM
#2
AudiWorld Super User
It's fine. The ECU will adjust the timing to avoid knocking. You'll be down on power until you burned through the tank, but that's mostly it. Don't expect top performance out of the car until you put premium in it again.
07-26-2017, 10:42 AM
#4
AudiWorld Senior Member
You'll be fine. I've driven many Audi loaners and i put the cheap gas in them and I've never had any issues. I'm sure most people put the cheap gas in it as well.
07-26-2017, 12:20 PM
#6
AudiWorld Senior Member
No harm. Just don't drive it hard until you clear out that fuel. New tank go 91 or 93. By 2nd tank of 91 or 93 it'll be like nothing happened.
07-27-2017, 08:21 PM
#7
Hi Everyone: By accident I filled almost my entire tank with 87 octane. I just finished the tank on mostly a long distance trip. I now have about 2,500 miles on the car. Noticed a little bit lower mpg. But is my engine, etc. going to be OK? Just want to make sure. Thanks everyone! -David
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07-27-2017, 09:30 PM
#8
The octane makes a much bigger difference under heavy load, i.e. hard acceleration. This is especially true when it's hot out and your engine is heat soaked. This is furthermore exacerbated in a forced induction application like our turbo cars since the intake charge is compressed by the turbo in order to provide more power output from a small engine.
Essentially octane rating in the US is represented as AKI (Anti Knock Index) which is the average of research and motor octane ratings, hence why you see the formula (R+M)/2 on pumps. In Europe they generally show you the R (research) rating which is a higher number, leading people to believe they have much higher octane.
The reason we call it anti knock, is because octane prevent's knock. It's the fuel's resistance to detonating under compression in the engine. When does knock happen? When compression, aggressive ignition timing, engine load and heat are factors. Why do we want to prevent knock? Because it's very damaging to the engine, especially in forced induction applications where we're asking a lot out of a 2.0L engine. Ultimately if you're just driving around like a normal person you're not requiring as much protection from high octane fuel as someone who is hard on their car.
If you go out on a hot day with your A4 and start thrashing it around, you're going to get knock on 87 almost immediately. Hell it will probably knock at wide open throttle on a cold engine. So when this happens the computer detects knock using a knock sensor (basically a microphone) and retards ignition timing which causes a drop in engine performance. While this saves the engine it's important to remember that knock retard is a reactive function, knock happens THEN the timing is retarded to prevent further knock. So the idea that it doesn't matter and you can just ride the knock sensor on low octane fuel without doing any damage isn't strictly true. You are causing damage, just not as rapidly as without knock sensors and knock retard to ignition timing. Computers are very fast now and getting the wrong fuel once on a factory tuned car, even if you beat on it, is unlikely to be problematic.
On my 820hp track car I have to run high octane race fuel, because it's a forced induction application and you're heat soaked on the track the entire time. I use octane ratings as high as 104 AKI unleaded.
Last edited by oesman; 07-27-2017 at 09:33 PM.
07-28-2017, 04:40 AM
#9
AudiWorld Member
I was just considering this issue earlier in the week when I went to fill up my Silvercar 2017 A4. As a fellow 17 A4 owner, I felt some obligation to put in 91 octane even though it was a rental. Because Silvercar was nice enough to give me this car with 15 miles on it (I was the first renter to drive it), I was nice and spent the extra couple of dollars to put in the higher grade.
I wonder what percentage of Silvercar renters refuel with the higher octane? My guess is a very small percentage. If so, and considering how many Audis Silvercar owns, putting in lower octane must not be a problem for the engine.
I wonder what percentage of Silvercar renters refuel with the higher octane? My guess is a very small percentage. If so, and considering how many Audis Silvercar owns, putting in lower octane must not be a problem for the engine.
07-28-2017, 04:41 AM
#10
AudiWorld Member
Wow, that was a great explanation. Very educational. Thanks for sharing!
If you're not running your car hard you haven't done any damage. Even if you did for one tank you wouldn't have done much damage on a factory tune/boost/fueling.
The octane makes a much bigger difference under heavy load, i.e. hard acceleration. This is especially true when it's hot out and your engine is heat soaked. This is furthermore exacerbated in a forced induction application like our turbo cars since the intake charge is compressed by the turbo in order to provide more power output from a small engine.
Essentially octane rating in the US is represented as AKI (Anti Knock Index) which is the average of research and motor octane ratings, hence why you see the formula (R+M)/2 on pumps. In Europe they generally show you the R (research) rating which is a higher number, leading people to believe they have much higher octane.
The reason we call it anti knock, is because octane prevent's knock. It's the fuel's resistance to detonating under compression in the engine. When does knock happen? When compression, aggressive ignition timing, engine load and heat are factors. Why do we want to prevent knock? Because it's very damaging to the engine, especially in forced induction applications where we're asking a lot out of a 2.0L engine. Ultimately if you're just driving around like a normal person you're not requiring as much protection from high octane fuel as someone who is hard on their car.
If you go out on a hot day with your A4 and start thrashing it around, you're going to get knock on 87 almost immediately. Hell it will probably knock at wide open throttle on a cold engine. So when this happens the computer detects knock using a knock sensor (basically a microphone) and retards ignition timing which causes a drop in engine performance. While this saves the engine it's important to remember that knock retard is a reactive function, knock happens THEN the timing is retarded to prevent further knock. So the idea that it doesn't matter and you can just ride the knock sensor on low octane fuel without doing any damage isn't strictly true. You are causing damage, just not as rapidly as without knock sensors and knock retard to ignition timing. Computers are very fast now and getting the wrong fuel once on a factory tuned car, even if you beat on it, is unlikely to be problematic.
On my 820hp track car I have to run high octane race fuel, because it's a forced induction application and you're heat soaked on the track the entire time. I use octane ratings as high as 104 AKI unleaded.
The octane makes a much bigger difference under heavy load, i.e. hard acceleration. This is especially true when it's hot out and your engine is heat soaked. This is furthermore exacerbated in a forced induction application like our turbo cars since the intake charge is compressed by the turbo in order to provide more power output from a small engine.
Essentially octane rating in the US is represented as AKI (Anti Knock Index) which is the average of research and motor octane ratings, hence why you see the formula (R+M)/2 on pumps. In Europe they generally show you the R (research) rating which is a higher number, leading people to believe they have much higher octane.
The reason we call it anti knock, is because octane prevent's knock. It's the fuel's resistance to detonating under compression in the engine. When does knock happen? When compression, aggressive ignition timing, engine load and heat are factors. Why do we want to prevent knock? Because it's very damaging to the engine, especially in forced induction applications where we're asking a lot out of a 2.0L engine. Ultimately if you're just driving around like a normal person you're not requiring as much protection from high octane fuel as someone who is hard on their car.
If you go out on a hot day with your A4 and start thrashing it around, you're going to get knock on 87 almost immediately. Hell it will probably knock at wide open throttle on a cold engine. So when this happens the computer detects knock using a knock sensor (basically a microphone) and retards ignition timing which causes a drop in engine performance. While this saves the engine it's important to remember that knock retard is a reactive function, knock happens THEN the timing is retarded to prevent further knock. So the idea that it doesn't matter and you can just ride the knock sensor on low octane fuel without doing any damage isn't strictly true. You are causing damage, just not as rapidly as without knock sensors and knock retard to ignition timing. Computers are very fast now and getting the wrong fuel once on a factory tuned car, even if you beat on it, is unlikely to be problematic.
On my 820hp track car I have to run high octane race fuel, because it's a forced induction application and you're heat soaked on the track the entire time. I use octane ratings as high as 104 AKI unleaded.