Premium fuel

My wife has a 07 VW Passat 6 cyl. The salesman said we need to use premium gas. Is it nessesary to use premium and will it hurt the engine to use regular?

Thank you, Marty

Car salesman=very poor source of information.

Owner’s Manual=the best possible source of information.

Open the glove compartment and read the relevant section of the Owner’s Manual. And, while you are at it, I would suggest that you also read other sections of the manual regarding the safe and economical operation of your car.

Those who ignore the Owner’s Manual invariably live to regret that omission.

When you get done reading the owners manual, enter “premium fuel” in the search window at the top of this board and read the 3000 posts that cover this subject in fine detail…

Premium (91) grade on a V6? It’ll help mostly for long-distance highway driving (little city driving, if that’s your route) & it burns less. But if it’s for mostly city & half the time highway, I would use mid-grade (89) for optimal performance.

Why? The higher the octane fuel, the better the compression is for your V6. I own both a Toyota Camry & a Toyota Highlander, both have a V6 engine. If you use a regular (87) grade, you burn a lot of gas for your usual driving since your engine works VERY hard & therefore pinging could occur if you use regular grade at every fill up.

Look inside the fuel door, it typically says Premium recommended or required. REQUIRED use it, recommended means optimal but optional. Its a meager $0.20 more in my area, the same price difference when I got my first car in 1988 and premium fuel was $1.25/gallon and regular was $1.05/gallon.

If the owner’s manual says it needs premium, it does. If it says it should have it then it should.

When it says it should have it (recommended) then it means you will get better power and likely mileage with it, but no damage will result.

When it says required, it means the above plus there is a possibility of engine damage if you don’t.

Why by a car that needs or should have premium and then not use it???

Use premium until your warranty expires. It’s cheap insurance against the dealer claiming that you messed the car up by using lower octane fuel if you ever have problems.

no no no, use premium, as is recommended/required. the small difference in price is hardly worth the risk of problems to your engine. Besides, fuel economy will drop enough to more than offset the cost savings.

With the type of engine in the car, I would recommend using the premium. You might get lucky if it says regular fuel, but if it says anything else, you had better use the gooder stuff. Just think of it as the best bottled water. In fact, you could pay for the gas if you quit the bottled water. What’s wrong with fluoride and chemicals at no extra charge?

VDC’s post was excellent. Use what your owner’s manual recommends.

Regular detonates more readily that premium.

If your engine is high compression (many new engines use supplementary compressors to boost compression, some are sctually higher compression via the mechanical ratio in the chamber) than premium will be required because the heat created when the fuel is compressed may actually trigger ignition before the spark plug does. If you use regular in these cases it can cause engine damage. In these engines premium will be “required”.

If your engine is only modestly higher compression, it may be just high enough to trigger a secondary ignition after the spark plug fires when the wave front propogates in the chamber, causing pinging. Longterm pinging causes internal damage. In these cases, your engine may be able to compensate by retarding the spark a bit. It senses the shock from the wavefronts clashing (with a “knock sensor”) and retards the spark. In these engines you may be able to run lower octane without damage, but your performance and mileage will suffer. In these cases premium may be “recommended” but not “required”.

In regular compression engines, regular fuel can be used without preignition, because the heat created from the compression doesn’t get too high and the combustion is fully controlled by the spark.

The owner’s manual is written by the guys who know the real correct answer.

The computer will automatically retard the spark to eleminate knock. Therefore you will get less mileage (and power)with regular, and if the retard doesn’t do enough you could get actual pinging, which is bad for your engine. You can’t rely on you ears–knock occurs before it is actually audible. If you only drove on flat highways at constant speed the regular would be ok, but that isn’t the case.

Then use it after the warranty to keep from damaging your engine.

The AAGS (American Association of Gasoline Siphoners) is working to get a federal law past that either makes it illegal to use regular in a car the requires premium, or have the owner put a sticker on the gas filler that indicates that regular has been put in the tank of a car requiring premium. If you want to tear up your car, that’s fine, but don’t damage the engine of those who “borrow” your gas when they have a car that requires premium.

(This is no sillier than some other laws on the books.)

From the website, (and I quote):

“Premium fuel recommended for maximum performance”

From me: If that’s what the manufacturer says, do it.


“The computer will automatically retard the spark to eleminate knock.”

That is true for all those cars that "recommend" premium, but it is not always true for those cars that the manufacturer specifies premium as opposed to recommending it.  On those cars that require premium, they likely also can retard the spark, but not enough under all conditions to protect the engine. I would not want to take the chance.