Mercury Milan Map Light Bulb Size

The Mercury Milan map light utilizes unique bulb sizes 6411, 578, and 12961 for interior illumination. Data for the specified components covers the range from 2006 to 2011.

The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.

Bulb Size by Year Range

Years	Bulb Size
2011	6411 (Front)
2011	578 (Rear)
2009-2010	12961 (Front)
2009-2010	578 (Rear)
2008	6411 (Front)
2008	578 (Rear)
2007	12961 (Front)
2007	578 (Rear)
2006	6411 (Front)
2006	578 (Rear)

Bulb Specifications

Description	Bulb Size
ANSI standard (US & Canada). Festoon bulb, 36mm length, SV8.5 base. 12V, 5W.	6411
ANSI standard (US & Canada). Festoon bulb, 41mm length, end-cap contacts. 12V, 12W.	578
Philips part number. Miniature wedge bulb (T10) with W2.1x9.5d base. 12V, 5W.	12961

Other Locations

Additional Notes

The rear map light position across all Mercury Milan model years from 2006-2011 uses the 578 bulb exclusively, making it the only consistent fitment across the entire production run covered by these specifications.
The 578 is a festoon-type bulb rated at 12V and 12W, with end-cap contacts rather than a pin or wedge base. At 41mm in length, it is physically longer than the 6411 festoon bulb used in some front positions.
The front map light position on the Mercury Milan alternates between two different bulb types depending on the model year, with the 6411 fitted in 2006, 2008, and 2011, and the 12961 fitted in 2007, 2009, and 2010.
The 6411 is an ANSI-standard festoon bulb rated at 12V and 5W, with a 36mm length and an SV8.5 base. Its shorter length and different base type make it physically incompatible with the 578 rear position despite both being festoon-style bulbs.
The 12961 is a Philips part number designation for a T10 miniature wedge bulb with a W2.1x9.5d base, rated at 12V and 5W. Unlike the 6411 and 578, it is not a festoon bulb and uses a wedge-style base for retention.
Because the front map light position on the Mercury Milan accepts either a festoon bulb (6411) or a wedge bulb (12961) depending on the year, the two front bulb types are not interchangeable with each other due to their differing base designs and physical form factors.
The 6411 and 12961 share the same 12V, 5W electrical rating, meaning the difference between the two front bulb types is one of physical form and base design rather than power consumption.
The 578 operates at 12W, which is more than double the 5W rating of both front map light bulbs. Substituting a 578 into a front socket designed for a 5W bulb would exceed the intended wattage for that circuit position.
The SV8.5 base on the 6411 refers to a festoon cap with an 8.5mm cap width, a standard designation used across many automotive interior lighting applications in North America.
Both the 6411 and 578 carry ANSI standard designations applicable in the US and Canada, while the 12961 is identified by a Philips part number, which is a manufacturer-specific reference rather than a universal industry code.