# regular or premium?



## damakkus (Apr 7, 2008)

Hi everybody.
I have just purchsed a 2001 Passat V6 4motion.
Since it came without the manual I'm on my own for now.
So my question would be does it really need the premium gasoline or is regular good enough?
Does anybody have some experience about longterm behavior with regular?
I assume that the engine controller is capable to adjust for regular. But does it cause some extra-repairs?
Thanks a lot everybody.


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## 96jettVR6 (Dec 16, 2007)

*Re: regular or premium? (damakkus)*

open your gas tank door.. it should say it on the inside of the door


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## damakkus (Apr 7, 2008)

*Re: regular or premium? (96jettVR6)*

Hi 96jettVR6.
Thanks for that hint. I have already discovered that sticker. My question is actually going beyond VW recommendation. My question was more related to experience to other drivers / technical people that have experience in this field. Usually engine controllers are capable to adjust for gasoline quality. Therefore the car is operating fine with regular.
But on the other hand the engine my have some long term issues with "poor" gasoline quality.
Any experiences put there?
Thanks again.


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## walkingfool (Mar 24, 2008)

*Re: regular or premium? (damakkus)*

Congrats on the 01 Passat 4Motion. My wife has 60K on hers and just loves it. She might not know WHY it runs well (or poorly) but she definitely lets me know when it needs a little hands-on work. (There was a slightly funky plug wire that precipitated an upgrade to a Neuspeed set about a year ago







)
She swears that it runs better on premium. So that's all it gets.
Dave


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## damakkus (Apr 7, 2008)

*Re: regular or premium? (walkingfool)*

Thanks walkingfool.
That's a start. So is everybody using premium because it's recommended?


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## YavoR32 (Jul 31, 2006)

Premium fuel is more pure, less ethanol right?


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## damakkus (Apr 7, 2008)

*Re: (YavoR32)*

I think there's a good explanation:
http://www.straightdope.com/columns/041008.html
Even this one details that it's worthwhile to discuss this topic further.


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## YavoR32 (Jul 31, 2006)

*Re: (YavoR32)*








wow i was wrong...


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## YavoR32 (Jul 31, 2006)

So would you use octane boost or fuel injector cleaners in your audi?


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## clarkma5 (Mar 2, 2002)

Octane has everything to do with the temperature at which the fuel combusts. Higher octane means higher temperatures are required to burn it.
Basically, higher octanes are required to prevent pre-detonation (pinging) in either high compression or forced induction cars. This is because high compression and forced induction cars see increased pressure in the combustion chamber, and one look at the ideal gas law (PV=nRT) should make it very clear that increasing pressure will also increase temperature. Thus, a low octane fuel will combust before the spark plug gets to fire in a high-pressure situation since its flashpoint is lower. Therefore you use higher octanes to prevent pre-detonation. In a modern car like your Passat, pre-detonation is prevented by knock sensors, which detect pre-detonation conditions and change the fuel and ignition timing to save your engine, at the expense of the engine's power.
However, you can go too far in the other direction too. Putting high octane in a lower compression engine will reduce the speed at which the fuel combusts in the chamber, and the longer the fuel takes to burn, the less effective the combustion is at producing power since the combustion chamber will be expanding away from the advancing firefront of the fuel/air mixture.
The Passat's 2.8 liter V6 has a compression ratio of 10.6:1, which I consider moderate. VW and Audi reccomend premium (91 RON) octane for this engine, but given the fact that the compression is sub-11 I would not hesitate one instant to put mid-grade in it. However, 87 octane tends to be ineffective in modern port-injected engines past 10.3:1 so I wouldn't use regular.
My friend's 3.0 liter Audi raised the same question and he switched back and forth between 89 and 91 octane on a whim and never had any issues worth speaking of with either one. Both seem to work quite well with VW/Audi's 30-valve V6s.


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## Roger2Texas (Mar 12, 2008)

*Re: regular or premium? (damakkus)*

When I first purchased my 03 Passat V6 last year, the used car dealer had no idea about the "premium gas" being required for my car, so I was never told anything. For a few hundred miles, I was using regular 87 until my check engine light came on, and I was furious being that I had just bought the car. I took it to a local mechanic and he reset the computers and asked if I was using premium, and he showed me on the inside of my gas tank door wher it shows fuel octane requirements, and ever since then (about 15k miles ago) I have not had any issues. And I've heard that if your car "requires" the premium, then it should be used. I just wish I would had known this before I bought the car, because I would have found something a little more economical. Good luck!!


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## damakkus (Apr 7, 2008)

*Re: regular or premium? (Roger2Texas)*

I also asked that question to VW. Their answer was actually that the engine could be destroyed by not using the premium. They added that the engine actually had been designed for this kind of fuel. So I guess in summary we just have to live and fill with it.
Doesn't look as if they had been able to implement a different control-mechanism for excessive knock. But even that would most likely just result in lower mpg.


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## feels_road (Jan 27, 2005)

*Re: regular or premium? (damakkus)*

I have the 2000 version.
I can tell you from over 100,000 miles of real-world experience that the car both runs better and gets better mileage on CA premium (91) than anything below (87, 89). Not only does it get better mileage, but it gets _better mileage to significantly overcompensate the added cost of premium versus regular,_ about 20 to 30 cents or 5% to 7.5%, here.
This makes sense not only concerning the compression ratio and state of engine evolution, but also considering that those octane ratings are marginal in Europe (even considering their different system).
Can't tell you much about 93, although I would certainly try it out over several tanks and hopefully similar driving conditions. I just suggest to try it out yourself, given *your* driving style.
However, I would not put anything below 91 in it, unless you want to establish more data points.
Also, keep your tires inflated at 37+psi, and use good, VW-approved synthetic oil.


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## halfmoonclip (Jan 25, 2004)

*Re: regular or premium? (feels_road)*

I've been running my bride's Passat on 89 since the prices have been going up. Can't see any significant difference in mileage looking back thru' the logbook; pretty consistent high teens in town, mid twenties on the highway. I usually can do better in town than my wife; she considers that control under the right foot as a gas 'switch' rather than progressive pedal.
Not sure about power, either. It's hard to be objective when one trip over Beffert Mountain is just two up, and others are with a load.
Gotta tell you we have three six-cylinder engines in our house; two Jeep I-6s and the VeeDub. Not the same creatures at all. The Jeeps clatter all the time on regular, and it doesn't hurt a thing.
Moon


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## YavoR32 (Jul 31, 2006)

OMG, I should be using synthetic?!? time for a new forum. or not.


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## thetwodubheads (Dec 6, 2004)

*Re: (YavoR32)*

No experience with this motor, but I have found on my GTI like someone said earlier I get enough of a boost in fuel efficiency to compensate for the added cost at the pump. Honestly it only comes out to a couple bucks anyway.


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## BlueMk3VR6 (Aug 7, 2001)

*Re: (thetwodubheads)*

I have a 03 V6 and put 93 octane in it.


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## YavoR32 (Jul 31, 2006)

Couple of bucks? its like 60 dollars compared to 80, and i fill up every three days.


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## thetwodubheads (Dec 6, 2004)

*Re: (YavoR32)*

HOW BIG IS YOUR TANK!?!!?!?!?!!?
Seriously it's only $.20/gal more.... If you have a 15 gallon tank, that is only $3 Unless you guys get raped on premium fuel there... Hell here in Billings, it is common for it to only be $.15 more than regular.


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