Is premium grade fuel necessary for VW Passat

A few weeks ago on the show, I heard the boys dismissing the need to use premium grade fuel because today’s cars can self-adjust the timing to prevent knocking. I have a 2007 4 cyl. 2.0 L turbo Passat wagon. I started using mid-grade gas about 2 weeks ago as a test and have had no knocking and almost the same gas mileage. Today my engine light came on indicating some problems with emissions!!!

Have I screwed up? I have visions of destroying the catalytic converters or some major problem. Help.

That CEL (check engine light) is just a kid in class waving her hand trying to get you attention because she has the answer. You need to have the codes read. Some places will read them for FREE. Try Autozone or Advanced Auto Parts. Get the exact code not just their translation into English and post it back here.

As for rather it needs premium, that answer should be in the bible aka Owner’s manual. It it says it needs premium, use it. Many if not most modern cars say it is recommended.

Not using it when it is required may cost you an engine. Not using it when it is required (these are the ones that adjust the timing using sensors) means you will loose some power and some mileage. How much depends on the specific car, the attitude you drive at and your driving habits.

Frankly I find it really strange that someone would buy a high performance car, to turn around and cheap out on the fuel loosing performance and likely some mileage meaning they will not save as much as they think.

In any case, good luck.

It’s the turbo model so it is very likely it needs 91+ octane AND full synthetic oil.
this is why I won’t touch a used turbo charged car.

Thanks for your comments. I will lose the idea of mid-grade and get back to premium.

When you start adding turbos to enhance performance, you are starting to pushing the actual engine design into the upper ends where tolerance to various fuel grades gets less and less. If you had a non-turbo, I’d say run the lower grade stuff, but the small turbos are more finicky. Switch back and see if it is happier (ie, no light). But get the error codes read first to make sure it’s not some coincidence.

Go to and find out everything there is to know about Passats.

When the car talk boys are saying that premium fuel is not necessary, I’m thinking that they are talking about the people who ask if the premium is better and if it should be used when it is not specifically called for by the manufacturer. In the old days of the seventies (the decade, not my age) I would run low octane unless the engine would not shut off, then I would use premium just to get it to shut off. Some engines would run great and shut off with low octane fuel. Chryslers would do alright until a hole was blown through a piston in their old ten to one compression engines. Now, you can’t tell by whether or not the engine will shut off normally. So if the manufacturer calls for a specific fuel, you would be better off using it. You get the blame this time until it is proven to not be your choice of gasoline that caused it. You may not be guilty after all.

If your owners manual and the fuel cap state premium fuel they say so for a good reason. That being what the manufacturer feels the engine runs best with. (Fuel mileage, etc.)

“The boys” are very entertaining, but refer to your owner’s manual for the correct fuel to use in your car. Do you listen to Jay Leno to get the national news?

I just bought a 1999 Passat 1.8 Turbo a couple of months ago. I did practically the same thing, and filled 'er up with regular gas the first time I had to fill up the tank. I wasn’t trying to be cheap or anything, I just really didn’t know that it mattered. Well, it really didn’t like the regular gas. It started to idle rough (the rpms going all over the place if I idled for more than 10 seconds), it would hesitate and buck when accelerating out of a full stop, and it would drop power while driving down the street or on the freeway. I siphoned the regular gas out and refilled it with premium, but, the problems remained the same even with the new gas. The check engine light never came on. I took it to the shop and they found nothing wrong with it. They said I had a cracked ignition coil and a broken temperature gauge which have now been replaced. But, the problems still persist! It is so expensive to take it to the shop, and they didn’t find the problem last time, what if they still can’t figure out what’s wrong with it? Research shows that it might be the Mass Air Flow. I’m just hoping there’s someway to make this car happy again.

In commiseration.