Car Slower after service B at dealer...
 

I am lost and I need some help...I am so depressed.

Recently took my car for service B at the stealership...They ended up just changing the oil. I live in a tropical country so I didn't mind the 10w40 Mobil 1 they put.

As soon as I drive off the stealership, I noticed that the car had lost some grunt. Brushed it off, and thought it is probably just in my mind. A few minutes later when the oil heated up, I noticed that the car is shaking a bit more than usual. Not too much shaking that you would be sure that there is something wrong. It about 10% more shaking than the normal V8 shaking of the AMG.

Read through the forum, and found out the over filling of oil can cause shaking, and sure enough, at the stealership next day, the car was overfilled. They sucked out the oil till I was at the bottom of the top tab.

Took off, and noticed the car is not shaking as bad...but still more than normal, maybe 5% this time.

I was so curious about the loss in power, so I vboxed the car to confirm.

Ok, here are the figures for 60-130 MPH..

Stock C63 does around 12.7 sec
Tuned C63 does around 10.8 sec

My car is tuned but managed only a 11.4 best, and average of 11.6 and worse 11.8 result. Worst of all, while driving on the street on second gear, around 2500 RPM, when I floor it, the car used to feel like it wants to jump out of its skin...but now when I do it, it feels smooth but a lot slower and the wheels won't even lose grip!

I am disappointed to say the least. Need help as to what I should check first. The 1 second difference from stock is too much for the tune to be erased, and the stealer said they didn't update my file, just cleared codes and reset whatever...couldn't get a straight answer anyway. But 1 second slower from other cars with the same exact tune from the same exact tuner is just too much for engine variations.

Any advice would be appreciated...

I think that maybe they reflashed your ECU.

Are you sure you are not in C mode?

I'd say it comes down to a few things:
1) 10w40 is thicker than 0w40. That's going to cause your engine to slow down a little (probably not nearly as much as it has)
2) If they overfilled your car right after a reset, the car has learned how to operate with too much oil. Now that it has a regular amount of oil, drive it around for a while and let it learn itself again.
3) Perhaps they flashed over your tune, but I really doubt it...

You may also have just gotten some bad gas...

Is it even worth checking the spark plugs? Would a bad plug cause the mild shaking that I feel when the engine warms up?

Yup. all runs were made with the AC off. ESP sport. The fastest run of 11.4 was done in M mode, while the others were done is S mode.

So what would make a car slower by 1 second in 60-130, slower in the mid range RPM, and cause slightly more vibration at idle?

What is the temperature and humidity level? Summer is a thief that steals away a significant amount of power from these motors.

It sure does. I've been driving in 100f weather since March, and boy do I feel it.

How much effect on the 60-130 time could that kind of temp do compared to lets say 50f ?

50f is a godsend. But my guess would be about 50hp loss at 100f. If you can see mirages on the highway, means it's bad.

Car felt so different in the winter.

Been doing it in the evenings on a tropical country...I am guessing around 90F.

The other cars did it on about the same temp though...

I just got my car in May and in July here, high 30s everyday, you sure feel it, the car sometimes feels lethargic.