It really depends on the usage that your are considering.
Is it something for under the hood, dash wiring, or speakers.
If it is is a data signal or something sensitive to EMI (Electro magnetic Interference) you may also want to use a twisted pair with shielding. below are a few of the most common types and usage. Generally I use UL1015 wire for most lower current applications.
1.“GPT” or “Primary” Wire
This is the most common wire you find at auto stores. As its name implies, it is a good general purpose automotive wire. It features a multi stranded core and flexible insulation making it ideal for pulling through tight spaces. It is usually rated to 80ºC (176ºF). Although some is also rated to 105ºC (221ºF). It is resistant to oil, chemicals and acids.
2.“1015” “Hook-Up” or “Motor” Wire
The biggest difference between GPT and Motor wire is that motor wire features finer strands of wire. This allows it to handle higher voltages.
Motor wire is rated at 600 Volts with a temperature rating of 105ºC (221ºF). It is resistant to grease, oil, acids, water, solvents, fungus.
Although most commonly used as internal wiring in appliances and HVAC equipment, motor wire is finding increasing use in automotive applications.
3. SXL Wire
SXL Wire features a cross linked polyethylene jacket that can withstand higher heat, abrasion, and aging than GPT wire. It is often the preferred choice in higher stress applications like race or industrial use vehicles. If you are looking for extra durability, this is a good choice.
GXL and TXL wire feature the same type of insulation but thinner walls to make it easier to pull through tight spaces.
