Originally I had 55/60W Halogens in my Euro headlights, then I tried the 90/130W and I did not see much improvement. Then I found the OSRAM Coolblue +10% Blue 4000K 55/60W H4 bulbs. These bulbs have a very distinct white output light which is much stronger then the original 55/60 halogens even though the current consumption is the same, and so no problems with the bulb-out detector module. The glass bulbs only have a very slight darkish blue/gray tint (they are not painted on blue like most cheap so called "Xenon" bulbs).

I've been tempted to wire a relay to each lamp so the Low beam will stay on when one switches to High beam, but frankly these OSRAM bulbs have such a high true white light output that I rarely find myself using the High beams at all.

I also purchased the H3 Coolblue +10% bulbs for the fog lights, and later even found the smaller 5W bulbs for the "Citylights" of the Euro headlamps and replaced the original ones which where adding a bit of yellow light to the H4 output.

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W163 ML230 EURO SPEC 1999
W124 300E 1986