FWIW, I checked in the 300M service manual and DC is quite NON-specific about the Indiglo details. Just says illumination integrated with the gage cluster and shows six bulbs. The replacement bulb(s) is # 194, no idea of the specs. Does NOT appear to need extra support electronics. It does note that some bulbs are halogen and not to touch them but not specifically the 194. IMHO,the 300M has the, by far, BEST gage illumination I have ever seen in ANY car. VERY easy to see at a glance, day, night or in between plus covering a wider, than I need, adjustment range.
