Ariens Gravely CAP- FUEL 03859100

What It Is

The Ariens Gravely CAP-FUEL 03859100 is a replacement fuel cap designed for Ariens and Gravely zero-turn mowers and tractors. It seals the fuel tank to prevent spillage, evaporation, and debris ingress during operation.

Fitment & Compatibility

Before buying, verify your machine’s model and serial number. This cap fits select Ariens and Gravely mowers, primarily those with a 2.5-gallon or 3-gallon fuel tank. Check the OEM part number cross-reference: 03859100 replaces older versions like 03859100A. Measure your current cap’s outer diameter (approximately 2.5 inches) and thread pitch (standard SAE). It is not universal—will not fit older Gravely models with a different thread pattern or larger tank openings. Confirm your machine’s deck size is irrelevant; this is a tank cap, not a deck part. Use Ariens/Gravely’s online parts lookup with your model number (e.g., 915xxx, 917xxx) for exact fit.

Key Things to Know

• Quality: OEM part, so fit and seal are reliable. Some users report the plastic feels thinner than older caps, but it seals well when fully tightened.
• Installation: Dead simple—unscrew old cap, screw on new one. No tools needed. Tighten until snug; do not overtighten to avoid cracking the plastic.
• Common gotcha: This cap is not vented. If your mower has a vented tank (some older models), you may need a separate vent kit. Check your original cap for a small hole or breather.
• Warranty note: Using a non-OEM cap can void fuel system warranty on newer models. This OEM cap avoids that risk.

Should You Buy It

Buy this if you need a direct, no-guess replacement for an Ariens or Gravely mower that matches the 03859100 part number. It’s a simple, affordable fix for a worn or lost cap. Skip it if you have a universal tank or a vented system—then look for a cap with a breather or a vent kit.