My dad drives an '06 CDI and says he gets better fuel mileage in Comfort mode as well and he finds it more comfortable.

I haven't noticed a big difference in shifting all that much between C and S though, whenever I drive his car.

Fun fact: For the longest time we assumed S stood for "Sport". We couldn't figure out what C meant though, until finally someone decided to leaf through the user manual. We all had an: "oooooohhhhhhh, that's what it means" moment...

Apparently C is supposed to take off in second gear, so it should be more comfortable in stop&go traffic.

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"The MB W123 is so bulletproof, you can drive them forever. Which is a good thing as it takes that long to get anywhere."
Betsie: 1984 W123 300D (hobby, 280k miles)
Myrla: 2001 Mazda Protege 2.0 ES 5spd (daily driver, 130k miles)
The Turd: 2007 Toyota Camry (wife's car, 118k miles)

It doesn't make sense to start off in 2nd gear, unless there's icy/snowy surfaces, and even then the car has traction control engaged. The car has to work harder to get moving in 2nd, so it wouldn't make sense that it automatically gets better mpg. That's a hard one to prove better mpg locking out 1st. Any defined data your Dad has, I'd like to look it over.

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'06 E320 CDI
'17 Corvette Stingray Vert