The one MB I've owned puts out about 13.25-13.30 at idle with engine fully warmed up. It reads higher after initial startup when cold. It read a bit higher a few yrs. ago. I suspect a set of brushes might kick it back up. One of these days I'll deal with that.
All of the Asian cars I've owned read much higher than my MB. Readings in the high 13's to low 14's are not uncommon in Honda and Toyota vehicles and these are cars with MANY miles on them.
1991 300-SEL - Model 126
M103 - SOHC
James Madison - Oppressors can tyrannize only when they achieve a standing army, an enslaved press, and a disarmed populace.
Liberty Firearms Training - After years of trying to regulate California criminals with a never ending stream of gun control laws they have still not given up with the belief that if they make something a crime that criminals will miraculously start obeying the law.