faheemw

Hello guys,

So - as the headline/subject line reads... wanted to get general consensus on what you use and the whole debate of premium vs regular.

Yes, I am aware that the "recommended" fuel to use is premium and that what it says in the manual, however, we all know we can also use regular as well.

My wife usually drives the Q5 and its mostly city driving so it pains me to use premium when the driving does not demand that sort of performance from the car. I would totally not mind filling up premium if we are on a road trip or car is going to be driven on the highway at higher speeds. I hate paying that extra 6-8 bucks for premium for every fill up - it really adds on. According to this article: http://finance.yahoo.com/news/as-gas...150553933.html we are getting suckered anyway.

So please - help me convince my wife that regular is okay for the city driving she does. Trust me - we have had arguments for this because she always likes to "play by the books" and do exactly as the manual says

We have only used premium so far - so if its okay to use regular on this car, is it okay to switch now? Is it okay to mix regular with the quarter tank of premium thats already in there? How about the middle one 89?

Thoughts?

F

Don Keener

Regular or Premium? - Feature - Car and Driver

In my car that is designed for and recommends premium, I run premium. If I didnt want to pay for premium, I would have bought a RAV4.

ex-quattro PETE

The owner's manual is pretty clear that the use of 87 octane gasoline is allowed, so you're still "playing by the book" if you use it, IMO.

With that said, based on my own experience, whenever I ran regular gasoline in applications that called for premium, this resulted in increased fuel consumption (not to mention reduced performance), so I wasn't really saving anything by running regular.

We use premium in our Q5, and intend to continue doing so. But yeah, the price difference for premium nowadays ticks me off greatly. Thanks for the link to the article.

idale

The engine will tolerate less than 91 octane, but unless things have changed recently the timing retardation is a reactive process rather than proactive, and keeps trying to increase timing to "normal" but bumping down after detecting knocking. Since it retards the timing after knocking occurs it's safer than in vehicles without knock detection, but since knock is still happening (just less than otherwise) it's still causing additional wear.

In any of my vehicles that required premium, I ran premium. If I wasn't okay with that I would've bought another vehicle. With German vehicles especially you want to play by the book to keep everything running in top form. Not to mention that city driving is typically harder on the engine with all the stopping and starting and more time spent accelerating, so it would probably actually make more sense to make sure and use premium for city driving rather than sitting at a constant RPM on the highway or something.

acadianbob

I have to agree that my previous S4 and current Q5 do better on premium. Better performance and better fuel mileage.

HaveBullDogWillTravel

I've read perhaps 25 threads on various car forums on this same topic...it's been discussed to death.
These threads are always started by cheapskates wanting to save a few bucks a month. You say it "pains me"? C'mon...you're still pained even after the price of gas has come down to half what it was? This makes no sense.
And according to that article, "so premium grades don’t re-price as quickly as petroleum prices fall." This means the difference is high now but prices will settle. I just checked fuel prices here and there's about 33 cents diff. across the board between reg. and prem. at most retailers.

Use what the manufacturer recommends...they are smarter than you.
Listen to your wife...she's smarter than you. You admit that she drives it more than you. Give your wife what she wants...she deserves it. She's not a penny-pinching cheapskate. I like the way she thinks.

SQive

Yup...if you have to use regular, better on the highway than around town.
I have seen the same thing. Octane in gasoline is intended to keep the fuel from igniting under pressure, the opposite of diesel. That way it doesn't ignite until the spark is applied.
If you run less than the recommended octane fuel, the only way the computer has to deal with it is by reducing the intake boost (T engines) to reduce the compression ratio. It tries to retard the timing, but the fuel is detonating before the spark, so what's the point? The resulting suck in fuel consumption is slightly greater, cost-wise, than just paying the extra for the recommended fuel.

newmoon

It's actually the opposite. You are putting more load on the engine when accelerating for city driving, than you are on the highway just maintaining a steady speed. That's why cars generally use more gas in city driving than highway driving.

The risk of engine knocking also increases when you put more load on the engine. Therefore, you should use premium if you mostly do city driving. The engine can cope with regular octane if it detects knock (after it has already occurred) by retarding ignition timing or reducing boost pressure, but then the engine won't be running at peak efficiency and you may end up using more gas to compensate.

Having said that, I have personally experimented with running 89 octane mostly on the HIGHWAY in my A6 2.0T. I did two tankfuls in the Summer and got:

555.1 mi / 17.300 gal = 32.1 mpg. Avg speed 41 mph
562.5 mi / 17.623 gal = 31.9 mpg. Avg speed 44 mph

I have tracked every other tank using 93 octane on fuelly.com and my overall average over the 27,000 miles is 31.4 mpg (includes city driving as well). So there really wasn't any detectable difference in mileage outside of normal variability, when using 89 octane on the highway.

I am not game to try lower octane in city driving however. I did get some engine knocking when accelerating fairly rapidly, even while I was using 93 octane!

lmariorod

Premium all the way. Just traded in our '10 Q5 and in 88K miles, it only drank premium. And usually Top Tier Shells V-Power at that. Now that's even pricier premium. The 3.2 never knocked and always ran strong.

BTW, never carbon build-up issues also.

At 76k I changed the plugs and they were showing a nice clean burn.

Now have a similar NA V6 in the Acura RDX, and it too will see nothing but Top Tier premium most of the time.

hilld

Diesel......



j/k.....I use premium.