The Åudi Quattro -- MUST it have only premium gas?

[theHandpuppet]

My partner has a '98 Audi Quattro (6 cyl auto) and she dutifully puts premium grade in it as the owner's manual recommends. Question is, would using a mid-grade gasoline do? With gas prices the way they are, saving 10-15 cents per gallon would surely help, especially because she has to commute.

Thanks in advance for any advice!

[FM Arouet666]

1. It might ping on a lesser grade.

Audi, like other European cars, offers high rev small displacement engines which require the higher grades of gasoline. I know my Porsche needs it, I ping with 91 octane, the only grade available in my state, the user manual recommends 93. I add an octane supplement for better performance. You might try a mid grade, a 6 cyl engine without a turbo might not need the higher grades. My personal experience with the A4 2.0T, the wifes car, had me going back to the 93 octane. You could try mixing grades, a pain in the butt, but it might save a few bucks. Forget about the octane boost and a lower grade, the stuff costs 12$ a can for the NOS product.

Costs me 50$ to fill my tank now. Thanks GWB, whatever happened to jawboning those Arabs into opening up their spigots. Yep, Clinton was a bad guy, gas a 1.50$ a gallon. Glory day! Ooops, the new tactic, the democrats have caused the price of gas to sky rocket. All those environmental concerns, we need to drive SUVs and pollute, pollute, pollute. That is the American way. :puke:

[Book Lover]

3. $12/can for boost?

How big a can? I'm paying $3/16 oz.

[FM Arouet666]

4. Boost comes in many flavors

The NOS stuff I have tried is the most expensive, there are many others. Does it work? Who knows, I came across this post.

http://vca2.viperclub.org/forums/showflat.php?Cat=&Board=UBB14&Number=295761&page=0&view=collapsed&sb=5&o=&fpart=1

Don't waste your money on ANYONE's octane booster...The primary ingredient in octane boosters is TOLUENE, which has an octane rating 114...You can buy this for around $2.50 a gallon at any Fleet Farm or Tractor Supply...What octane rating are you shooting for? Do the math...

Mixtures with 92 Octane Premium
10%...........94.2 Octane
20%...........96.4 Octane
30%...........98.6 Octane

Xylene is also a cost effective solution, often mixed with Toluene and sold a "racing fuel"....Xylene has an octane rating of 117. Mix with 92 octane for the following ratings

10%...........94.5 Octane
20%...........97.0 Octane
30%...........99.5 Octane

Don't know if this chap is correct. I do know that the boost I buy does decrease pings. If you can live with the pings, will a lower octane hurt the engine?

[Book Lover]

2. Try a littel cost-benefit on buying the lower octane and

putting in octane boost. Depending on the size of the tank, etc, it may be a better deal(?)

[FM Arouet666]

5. See my other post.

You might be right, it would seem that most available boosts are identical in chemical composition. Price varies according to brand, but they all probably do the same thing.

[theHandpuppet]

6. Thanks all for the replies!

I'm going to pass along this info to my SO. :hi:

[dipsydoodle]

7. I had a 225 tt Roadster in 2000

Our UK unleaded does come in two grades but the higher grade is generally acknowledged as being an unnecessary rip off so so I always used the standard grade without any problems.
The engine management system sorts it out anyway.

At the same time I also has a 1927 Model A Sport Coupe but that was a different matter - need leaded fuel for that although I believe they will run on chicken shit. If by some fluke someone else in the UK has still got a Model A I've still got a load of Castrol XL and tractor oil for the steering box etc.

[Kolesar]

9. Yes, the engine has a knock sensor that signals the engine controller

So, according to the Car Talk Guys, an engine would probably run ok on low octane. They recommend just try it and see.

[MemphisTiger]

8. Give midgrade a try but don't be surprised when it pings

In that case drive it until it's on almost empty then put midgrade in it to about half a tank. If it drives bad, you can go and put premium gas in it to help dilute the mid grade and an octane booster wouldn't be a bad idea at that time. I almost bought a volvo that required premium gas, I'm glad I didn't now.

[LSK]

10. try mixing it up

One week premium, the other week middle range stuff.

The highest risk of damage would be at high rpms so dont go racing it or flooring it with lower octane gas.

[taught_me_patience]

11. Lets see....

.10 x 15 gal x 3 fillups/month x 12 months/year = $54/year extra for premium. Know this... engine knock is the number one killer of engines (especially high compression engines like Audi). $54/ year or 5k engine rebuild... your choice :shrug:

[benEzra]

12. Best case scenario - you'll lose power and possibly mileage.

Worst case scenario - you get pinging (detonation), which will definitely shorten the life of the engine.

As others have mentioned, the Audi engine uses a higher compression ratio than a lower-performance engine, meaning better power AND better economy, but the downside is that it must use fuel that is more resistant to predetonation. The octane rating of gasoline is a measure of that quality.

If the car's computer is really on the ball, it will sense predetonation and dial back the spark timing to reduce the risk of it reoccurring. That means lower performance and worse gas mileage. If the car's computer isn't on the ball (you have a bad knock sensor, for example), then detonation will continue to occur (you hear it as a gurgling or light knocking sound, easiest to hear at lower RPM's), and that is very, very bad for the engine.

My car requires premium, and I use it exclusively. The way I figure it, 15 gallons @ 3.20 a gallon vs. 15 gallons at 3.05 a gallon is only $2.25 per tank, and if you get a mileage hit from using lower-octane fuel, then the real difference will be even smaller. That really isn't much money, and to me the benefits of the higher octane fuel are worth $2.25 a tank, especially if you're driving an Audi...