I replaced my burnt 3057 bulb with a 3157 as my buddy had one handy. Any real difference -should I chnage it for a 3057? You can tell I know squat about all things electrical!

 

If you check the specs they seem to be the same bulb as far as wattage and dimensions. I do remember when Ford started selling Nissan minivans as Mercury Villagers, they took 2057 bulbs rather than the traditional 2157 bulbs. It turned out that the base on the 2057 was just a hair longer, and using the 2157's would cause the bulbs to not work intermittently. There must be a reason why two different bulbs are made, I would get the correct bulb.

 

The catalog I have lists the 3057 as 32.0/2.0 candle power and the 3157 as 32.0/3.0 cp. I interpret this as the running light on the 3157 is 1 cp brighter, which also means hotter. The brake light cp's are equal.