quote:maybe Garth has more research
No more research, but here's my logic...
1. We're only concerned about going from 5w to 8w for the running light; a small 3w difference.
2. The wires powering the light appear to be the same size/gauge. And, share the same source/power wire to the tail lights. Therefore, if the factory wiring can handle the original 21w load of the stock brake light, and the same wire size is shared with the 5w tail light, then I have no worries about it's ability to carry the extra 3w to power an 8w load for the new bulb.
3. Last, although "inexpensive" original incandescent bulbs were rated at 5w/21w, "premium" bulbs have been available and used for decades in all manner of cars using the 1157 tail/brake bulbs. These original-style "premium" incandescent bulbs are rated at 10w/27w, and I've not heard of any examples of the additional load causing problems, failures, fires, etc.
Last, history, or the experience of others, gives me peace of mind... Pantera people have been replacing the stock bulbs in their instruments/gauges with higher wattage bulbs (similar delta) for years without any ill affects to the wiring.
Anyway, that's my reasoning. YMMV!