I recently purchased a 94 Mercedes Benz E320 Sedan. The previous owner has always had all worked done at the dealer and used full synthetic oil and High octane gas. About a week after purchasing I decided to put medium grade gas into it and a couple days later the check engine light appeared. I will be running a diagnostic scan soon but does anyone know off hand if this is a common issue for these cars??:confused:

 

No, these models should be able to handle substandard gas. They have knock sensors.

You'll have to read the code generated for the check engine light before further comment. You can quite easily do this yourself. Here is a link to some useful information