Am replying to this old thread for the benefit of future viewers.
I've upgraded the boot and interior lighting in my S350.
There are two main things to consider when replacing conventional filament lamps with LEDs.
The first is colour temperature. A conventional filament has a colour temperature of around 2200-2700K (Kelvin) which is a warm yellowish light. 4000K is whiter, 6000K is cool white (daylight effect) and as the temperature increases it moves closer to a blueish light. Generally a higher temperature will
look brighter - even if they're still outputting the same amount of light.
The second is the actual light output which is measured in lumens, abbreviated to lm. A 5 watt filament lamp outputs about 50lm. Simply replacing with an LED will not necessarily produce more light since generally LEDs are marketed as energy saving and a w5w LED may only have a real (whatever the alleged specification says) wattage of 1watt and still produce 50lm - if you're lucky, given that the majority of cheap LEDs I've seen don't specify the real wattage or lumen output, although Halfords cheapies say 35lm - less than filament !
I've used the Philips Ultinon Pro6000 range and the 6000K colour temperature variant. Philips are the only reputable manufacturer I've found who quote the lumen output - 90lm for the w5w and 100lm for the 38mm festoon - which meant I was certain I'd get more light. The cheaper Ultinon Pro3000 range output is similar to filament lamps at about 50% of the 6000. They're not cheap, but the Pro6000 w5w 6000K prices on Amazon go up and down and I bought the w5w recently at £6.99 a pair - today they're £12.28 with used like new at £9.14 and £12.99 at Autobulbs, so keep an eye out for price drops. BTW the picture is wrong as the base isn't a w5w - this is because it's also wrong on the Philips website !!
Given the anxiety-inducing difficulty of removing (and chance of breaking
) the front and rear interior lamp covers I wasn't prepared to risk saving a few quid and having to do it again if/when the cheap bulbs failed.
However if I were to do it again I'd try to find reputable bulbs with different positioning of the LEDs. The Philips festoon only have the LEDs on one face - to get a more diffused light I'd look for both faces or an all round arrangement. The w5w have the LEDs on the top and sides and top, sides, front and back would be better. What isn't in doubt is the light output - looking directly at them is not recommended unless you want spots before your eyes for a while
I replaced the following bulbs:-
Boot 4 x w5w,
Glovebox w5w,
Central cubby w5w,
Front roof 2 x w5w - original filament are 6 watt,
Rear roof 2 x 38mm festoon - original filament are 6 watt,
Rear reading lights 2 x w5w - original filament are w5w type (6 watt?) with a silvered cap.
The LED w5w are longer than the originals which wasn't an issue apart from the rear reading lights, where the LEDs only just fit and are hard against the covers, maybe or a hair or two clearance. Given the lower wattage and heat output and occasional use I've taken a chance that they won't burn the covers. The front reading lamps in the mirror are already LED and the 6000K variant I used are a good colour match.
The two side boot lights, the glovebox and central cubby lamp covers were easy to pry out using a small electrian's-style screwdriver.
The two boot lights attached to the boot lid do NOT pry off - they're glued to the trim piece running the full width of the lid and covering the catch. There are four T20 screws to remove and two pin and split button plastic fixings at the outer edges - pry out the centre pin to release. When re-assembling, put the two outer plastic split pins in first, then push the trim piece up against the boot lid when tightening the four T20s to ensure a good fit. The lampholders want to catch on the cutouts in the trim, so don't force, a bit of wiggling is needed. Also the lampholders have two lugs that engage with the the lamp covers, they are of subtly difference sizes so there's a right way round - both lugs engaged - and a wrong way - one lug engaged. IIRC this applies to the other non-captive lampholders too.
The rear interior lamp covers are the most difficult to remove. Have a look at this video:-
S350 rear interior lamp cover removal
The screws fixing the grab handles are T20. The guy in the video uses a screwdriver to pry. I used a 10mm wide plastic pry tool from a cheap set from eBay that I already had. This had the benefit of needing to be less precise where I inserted it to contact the fasteners and less of a risk of damaging or marking my black headliner. Be prepared for terrifying noises which sound like you've broken something as you release each of the many lugs holding the lamp cover. The technique that worked for me is to insert and then pry down, towards the cover you're trying to remove, like in the video.
The front interior lamp covers need a similar technique using the small screwdriver, although the lugs are much smaller and less robust, so gently does it. They have four lugs each, located towards the corners on the longest sides.
I didn't see the need to replace the four footwell lights or the four vanity mirror lights and frankly CBA - my bad
