Date registered: Mar 2005
Vehicle: '01-E320 & 02-ST2
Location: John 15:18-19
Mentioned: 0 Post(s)
Quoted: 35 Post(s)
First, welcome to the forum.
Second, this is probably the most common issue brought up on the forum and it's usually tied to a rise in fuel prices. That said, generally speaking when you join pretty much any forum, rather than just posting a new thread on a topic, it's useful to see if there is a search function. This site has two, the built-in one as well as the google one (up by the ebay one). If you use that search function (the google one works better for this particular search) you'll find there are literally thousands of posts in hundreds of threads...on this exact topic.
Your engine was designed, engineered and built with a premium fuel requirement and that should be pretty clearly stated in your owner's manual. No one can tell you "exactly" what will happen if you choose to ignore the premium fuel requirement because there are lots of factors that go into it. (You will find lots of opinions on the topic, however...but you won't find any dealer that will suggest it is okay.) Negative consequences of using regular fuel for normal driving include (among other things) higher combustion temperatures, pre-ignition, higher emissions, reduced performance, reduced economy, carbon buildup, shortened life of O2 sensors and catalytic converters.
Even were you to take the time to read through all of the posts on this topic, you'd still end up having to make up your own mind which fuel you will use. But the general suggestion is to use what the designers intended, just as with oil, coolant and other such things, assuming, of course, that you want your car to last as long as possible with as few problems as possible.
Lastly, there is a forum that is specific to your classic roadster, if you slide down the main page you'll find lots of useful information and enthusiasts in the R129 forum.
Take care and enjoy the ride,
Socialism is a philosophy of failure, the creed of ignorance, and the gospel of envy; its inherent virtue is the equal sharing of misery. (Winston Churchill)