Southwire is North America's largest wire and cable manufacturer. Their automotive and marine wire products are trusted by OEMs, boat builders, and professional installers worldwide. Here's how to choose the right wire for your application.
Automotive Wire Types
GPT Wire (General Purpose Thermoplastic)
The standard for automotive wiring. PVC insulation rated for 60�C (140�F) continuous use. Available in all standard gauges from 22 AWG to 2 AWG. Suitable for interior wiring, accessory circuits, and protected underhood runs.
- Temperature rating: 60�C (140�F)
- Voltage rating: 60V
- Best for: Interior wiring, trailer lights, accessory installations, protected runs
- Not for: Direct underhood exposure near exhaust or extreme heat zones
GXL Wire (Cross-Linked Polyethylene)
Upgraded underhood wire with cross-linked polyethylene insulation - significantly more heat resistant than GPT. The industry standard for underhood primary wire.
- Temperature rating: 125�C (257�F)
- Voltage rating: 60V
- Best for: Underhood wiring, engine bay accessories, circuits near heat sources
- Advantage over GPT: Won't melt or shrink back from terminals in high-heat zones
SXL Wire (Standard Cross-Linked)
Similar to GXL but with a slightly thicker insulation wall for added abrasion resistance. Preferred for runs through grommets, metal conduit, or areas with potential chafing.
- Temperature rating: 125�C (257�F)
- Best for: Applications where abrasion resistance matters alongside heat resistance
Marine Wire
Tinned Copper Marine Wire (ABYC Standard)
For any boat or marine application, always use tinned copper wire. Bare copper corrodes rapidly in salt and humid marine environments - you'll see green corrosion at connections within months. Tinned wire (copper with a thin tin coating) resists corrosion for decades.
- Standard: ABYC E-11 (American Boat & Yacht Council)
- Insulation: Type 3 stranded (finely stranded for flexibility), UL 1426 rated
- Temperature rating: 60�C or 105�C depending on grade
- Best for: All marine DC wiring - bilge pumps, navigation lights, electronics
Wire Gauge Selection Guide
For 12V DC systems with max 3% voltage drop:
| Amps | 5 ft run | 10 ft run | 15 ft run | 20 ft run |
|---|---|---|---|---|
| 5A | 18 AWG | 18 AWG | 16 AWG | 14 AWG |
| 10A | 16 AWG | 14 AWG | 12 AWG | 12 AWG |
| 15A | 14 AWG | 12 AWG | 10 AWG | 10 AWG |
| 20A | 12 AWG | 10 AWG | 10 AWG | 8 AWG |
| 30A | 10 AWG | 8 AWG | 6 AWG | 6 AWG |
| 40A | 8 AWG | 6 AWG | 6 AWG | 4 AWG |
Wire Stranding: Solid vs Stranded
Always use stranded wire for automotive and marine applications - never solid wire. Solid wire work-hardens and breaks from vibration. Stranded wire flexes without fatigue. The finer the stranding (more strands of thinner wire), the more flexible and vibration-resistant.
Shop Southwire Automotive & Marine Wire
We carry Southwire GPT, GXL, SXL automotive wire and tinned copper marine wire in all gauges and colors.
