57K miles
Dealer found a misfire
Scoped heads and found cylinder #5 valve seats were worn due to worn guides.
Mentioned that MBZ has been having problems with ethanol fuel and valve guides.
Replaced head.

Has anyone heard of this concerning ethanol fuel and valve guide failure?

Thanks
Bob

 

There was a technical bulletin issued in August 2015 for worn valve guides on M278 engines. It doesn't provide any root cause details such as design , material or quality defect. However, it does say M278 engines with serial # 30 128000 and higher are affected.

I'm curious to know, what brand/octane of gasoline do you use in your GL?

 

Had the same issue on mine - Cyl#5 - had the head replaced. One heck of a job and expensive (no cost if warranty is still active). Long live extended warranty for these beasts.
Every dealer will say some odd reason however per the previous attached - i think there was a factory issue and they just cover it up to sway away from a recall..

 

91 octane major brands.

After reading about the TSB I believe this may be a factory issue they might be trying to cover up? I pity those who have had this problem after the warranty!

 

Actually, unless they find that your engine has the misfire symptom they won't just do the TSB for grins and giggles!

 

This would not be the first time that MB covering up a known issue affecting their vehicles.