Check engine light

I can't imagine that an 03 beetle requires premium fuel. What I need you to do is have the check engine light checked. If it is on, there is a code stored in the computer that will identify where the problem is coming from. Take the vehicle to a nationally recognized parts store. Most will scan it for free.

Let me know what you find.
Joe

Do you have a diesel engine? If you have a gas engine, the lower octane will not cause engine damage. Contrary to popular belief, higher octane fuel does not provide more horsepower. Higher octane fuels allow the designers to build and TUNE the engine for more horsepower. Those design modifications often result in a tendency for preignition. That's when the fuel self-ignites before the spark plug fires. Additives that result in a higher octane resist that preignition. With a lower octane, you might hear some knocking from the engine, particularly under heavy acceleration.

The lower octane fuel will mix with what was already in the tank so the actual octane value will be higher than 87. As soon as you add more fuel, the value will go up some more.

If you have a diesel engine, it won't even run on gasoline. If only a little gasoline was added, it would be wise to have the tank drained then refilled with diesel. Besides igniting way too easily from the high compression that is needed to ignite diesel fuel, gasoline does not provide the lubrication properties of diesel fuel oil. That lubrication is needed for the injectors, injector pump, and pistons.

Caradiodoc