everyone and their mother knows how gas prices are bad, and only going to get worse as summer comes around. but premium gas for a 560SEL? is it just a moral thing that you would only want to put the good stuff in the best cars or does it really have a huge effect on the engine?

stupid question i know but ive been wondering that for a long time..i dont want to go cheap and ruin my baby

 

believe me dont try it! one time i accidently put regular in my w126 cause i was in a hurry and OMG! it was not good!! accelaration went to ****!!! i mean the w126 arent monsters when it comes to accelaration but damn! i remember trying to cross the a highway and there was horrible throttle response since that day i have made sure to never put thing under 91 octane level

 

Octane measures the abilty of fuel to resist pre-detonation.

 

And as Goatman said, when detonation starts occuring out of sequence, then knocking starts. It will damage internal components if done for a significant amount of time. Meaning going up and down highway while the car is on severe knocking. It could eventually crack a piston and/or cause catasthropic failure. Not good for your checkbook!