I suggest upgrading to a better quality bulb. The standard bulbs in the 70's and most 80's are made with a poor quality, heavily leaded glass. These bulbs 'silver-over' very quickly and produce about 1/4 of the light they were intended to produce.
The purpose of the heavily leaded glass is to produce a cooler lamp and reduce the possibility of explosion in the instrument cluster...... A mess to clean up.
Lamps made in the late 80's and after are a better quality glass and do not turn color as easily. Lamps made today are far superior to those made just a few years ago. Just be sure to replace with the proper wattage!
[Edited by WmHarlow on 12-11-2000 at 03:47 PM]