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Because it may only be recommended for a condition that some people will never encounter. 91 octane is recommended because it is too complex for Audi to explain these conditions, and/or they would not be able to get the same EPA rating if they recommended a fuel that didn't cover the full EPA test condition.
But yeah, "Premium fuel required" means it is required. "Premium fuel recommended" means that the car has been designed to adapt to lower octane without damage. There are cars that require premium fuel. The Q7 is not one of them, but sometimes puts it to good use, such as when towing, at higher altitudes, at higher temperatures, and at lower humidity.
I am still doing my fuel economy test to see if I can measure a difference. So far on 87 I have not heard any unusual sounds. I have not compared fuels at the drag strip, but no one is going to feel a difference in acceleration.
Last edited by rsilvers129; 09-06-2017 at 06:02 AM.
I agree with you on this, I don't get it either but to each his own. Before I bought the vehicle I knew what the recommended octane rating was and was fine with using it. Even though the manual states I can use a lower octane I don't, others may feel I am wasting my money and that's fine, but for ME I prefer to use the higher octane.
I usually don't get into octane discussions simply because in all fairness it doesn't matter to me what gas someone puts in his or her vehicles.. If someone is comfortable putting 89 or 87 in their Q7, or any other vehicle for that fact it has no effect on me.
At least with the Q7 it is only recommended that you use the higher octane, and if you prefer you can use a lower octane and as per the manual the only effect it will have is a slight decrease in performance.
However, in some other auto forums I've read, even when the manufacturer states that "premium is required", and the manuals states that long term use of lower octane can lead to engine damage, there are always some people trying to convince everyone to use 87 because they do it and has no ill effect on the car. No thanks....
I'm not sure why anyone would go against the manufacturers recommendation. If they thought 87 was good enough, they'd not say use 91. Its a deterrence for many buyers who dont want to pay for premium fuel. I have 3 cars now that recommend/require premium and frankly I've gotten used to paying for premium that I dont even look at regular gas prices. Its the price you pay to drive nice cars...
I'm not sure why anyone would go against the manufacturers recommendation. If they thought 87 was good enough, they'd not say use 91.
Because octane requirements are dependent on temperature and other things, and they don't know if you are driving in 100 degree weather or 70 degree weather. For some drivers in some environments, there would be no difference. But since they don't know, they pick the octane that works in any condition.
Guys, this topic was discussed at one of VAG's technical forums some time ago. It comes down to the issue of variable fuel quality and availability around the globe. Not everyone has access to the quality of gasoline we do. Not everyone has access to high octane gasoline and the cars have to be able to run acceptably on essentially anything.
Yes but what I want to know is - what is being given up and when is that being given up to use 87 instead of 91?
It would be nice to have an Audi engineer say something like:
"We did testing, and below 90 degrees it doesn't matter, but it starts to matter above that, and you would give up about 13 HP, but only if you rev to over 4600 rpm, which only happens in Dynamic Mode. We saw no difference in the EPA fuel economy testing."
Yes but what I want to know is - what is being given up and when is that being given up to use 87 instead of 91?
It would be nice to have an Audi engineer say something like:
"We did testing, and below 90 degrees it doesn't matter, but it starts to matter above that, and you would give up about 13 HP, but only if you rev to over 4600 rpm, which only happens in Dynamic Mode. We saw no difference in the EPA fuel economy testing."
That would be perfect and easy for customers. So it will never happen
I'm not sure why anyone would go against the manufacturers recommendation. If they thought 87 was good enough, they'd not say use 91. Its a deterrence for many buyers who dont want to pay for premium fuel. I have 3 cars now that recommend/require premium and frankly I've gotten used to paying for premium that I dont even look at regular gas prices. Its the price you pay to drive nice cars...
I totally agree with you.. I have 4 vehicles in the household, 3 require premium and one (Q7) recommends it. They all get premium, and like you I also don't even look at 89 or 87, never have and probably never will. Last time I used regular gas was in a Lexus loaner years back.
I plan to keep my car for 10 years, and so if there was any chance of engine damage, I really would care. But I don't like innuendo and speculation. I would not consider 87 or 89 if the Q7 required 91 octane, but it doesn't, as far as I can tell.
It is not a factor because Audi says it is fine, and because it is designed to run on it without damage, and because no two used cars are the same, so I would get the one that didn't have a ding on the door.
This is right from the user manual:
WOW, this thread in general has left me very perplexed in general and somewhat concerned. But no criticism to anyone.
My thoughts on this as follows:
1. Higher octane fuel does not burn as easily as a lower octane fuel. Higher octane fuels are specified where higher compression ratios are present in an engine, or where forced induction (such as turbo charging) is used.
2. If you do end up using lower octane fuel you then rely on the knock sensor to compensate for the lag in timing. The engine was not designed to operate in this condition continuously. Prolonged use of low octane fuel in these engines, pinging or pre-detonation can occur and can eventually destroy the engine. Pre-detonation causes very hot conditions in your engine and can melt sparkplug and pistons
3. The spirit behind the text in the manual is that in the event where we have no other choice it's OK, but go back to the specified fuel at earliest opportunity.
Here is a question: if you are a performance runner what drink would you take after your sprint? Gatorade type drink or Tap water? Do you think your body just needs rehydration? Or does your body need to compensate loss of electrolytes that regulate your bioelectric balance as well?
The same analogy can be applied to the use of fuels in engines. If it wasn't designed for a specific fuel type then best not use it, at least long term.
I think when the car goes into retarded mode, it stays there for several gallons of fuel after the next fillup. It is not adjusted on the millisecond basis. So it is not in any state of continuous pre-detonation.
... there are always some people trying to convince everyone to use 87 because they do it and has no ill effect on the car. No thanks....
There is no one trying to convince you nor anyone else to use 87. You and everyone else can use whatever you want and I don't think anyone here really cares. I asked the original question because while I am waiting for my car to arrive I wanted to investigate what fuel to buy and where to get it. I asked for others experience using 89 and I got what I was looking for. The discussion was very helpful to me and in fact I have changed my position of what I am going to use.
If you are bored with it or don't like the discussion then don't click on the topic. This is an open forum. I appreciate the people that have posted positive comments both for and against using 87, 91 or whatever.
09-06-2017, 05:35 AM
