Greetings, Mercedes Benz enthusiasts.

At the beginning of this year I bought my 2005 Mercedes C240 4matic wagon. With slightly over 90,000 miles, I am the third owner. The car has been beautifully maintained and is in wonderful condition. So far I have put 2,468 miles on it, lightly driven.

I have been using mid-grade gas instead of premium, just having learned that only premium gas should be used. I'm a little under half a tank now. Should I fill it with premium now, or draw down toward empty the tank of mid-grade and then fill up with premium? Will the sensors readjust themselves and have I done any damage to mechanical system?

There are no warning lights and the car drives and handles beautifully.

Also, I have just learned here at this forum that washing and caring for the paint demands special care and attention. At first, during the winter with heavy road salt, I did go through automatic carwashes a few times until I noticed a few scratches that had not been there before. So I have been washing the car myself using ArmorAll Ultra Shine Wash & Wax. I am noticing that the paint is not as clear and vibrant as it was at first. Again, I hope I haven't damaged the paint. I have read the instructions here at MBWorld as to how to detail my car professionally DIY, and will follow the instructions carefully.

The car is now due for an oil change which will be done next week at an independent Mercedes Benz mechanic in my community. Meanwhile, I welcome advice from fellow Mercedes owners here at MBWorld.

There is a great deal to learn about how to expertly take care of a Mercedes, especially of the vintage of my C240. I absolutely love this car so want to baby and take care of it expertly!

I'm grateful to find this great resource for Mercedes owners.

Thank you for your help!

 

moved to W203 forum...

 

Just fill it up with premium now. The resulting mixture will be better than the mid-grade currently residing in your tank.

 

Welcome to wagon ownership
Don't worry at all about the gas, just use premium going forward.
And what I did when I got mine a few years ago is make a list of preventative maintenance work that needs doing to make it as reliable for the next 100k.
Almost always none of these sorts of repairs have been done on what to most people is some old used car.
So stuff like serpentine belt, cam sensors, motor and transmission mounts, all hoses for the pcv system and breather hoses, covers, MAF, spark plugs and coils and wires.
Of course there will likely be suspension work that needs attention at this age but your shop should be able to advise after an inspection.
I have honestly spent most of my time replacing the many many interior plastics that were made from eggshells apparently.
What saved me in this regard is a pull it yourself junkyard.
These cars were very popular and I was quite surprised at how many I found there.
Good luck!

 

Best car I ever owned....I have owned a lot. C240, wish I had never given it away.

As for fuel - that is one of the few cars that did not care. It has two sparkplugs per cyl - mine always ran fine no matter what I put into the tank.

 

Interesting theory about the spark plugs, I've not tried experimenting personally.

 

For me it was an accident. Frequently after storm no stations have premium and put regular in every tank....sometimes we have no choice.

 

Thank you! Your reply is much appreciated.