Peterbilt 330/335/337 Fuel Tank Caps

Frequently Asked Questions About Peterbilt 330/335/337 Fuel Tank Caps

Will these fuel tank caps fit my specific Peterbilt model year?

Our fuel tank caps are designed to fit Peterbilt 330, 335, and 337 models from 2005 to present. However, there were minor changes in tank neck designs between 2005-2007 and 2008+ models. Most caps are universal within this range, but we recommend checking your existing cap's thread size (typically 2.5" or 3.5" diameter) or contacting us with your OEM for exact fitment verification.

What's the difference between vented and non-vented fuel caps?

Vented caps allow air to enter the tank as fuel is consumed, preventing vacuum buildup that can cause fuel flow issues. Non-vented caps create a sealed system. Most Peterbilt 330/335/337 models require vented caps for proper operation. Using the wrong type can cause hard starting, stalling, or fuel gauge problems. Check your owner's manual or look for "VENTED" stamped on your original cap.

Are locking fuel caps worth the extra cost for these models?

Locking fuel caps are highly recommended for Peterbilt medium-duty trucks, especially for fleet operations or overnight parking. They prevent fuel theft and contamination from debris or water. Our locking caps use either keyed or combination mechanisms and maintain the same venting properties as standard caps. The typical $20-40 premium pays for itself by preventing even one instance of fuel theft or contamination.

How do I know if my fuel cap needs replacement?

Replace your fuel cap if you notice: fuel smell around the tank area, visible cracks in the rubber gasket, difficulty tightening or the cap won't click when turned, or rust/corrosion on metal components. A faulty cap can trigger emissions failures and reduce fuel economy by 1-2% due to evaporation.

Can I use aftermarket caps or should I stick with OEM?

Quality aftermarket caps that meet OEM specifications work perfectly for Peterbilt 330/335/337 models and often cost 40-60% less than dealer parts. Look for caps that specify SAE J1810 compliance and include proper O-ring seals. Our aftermarket options use the same materials (aluminum or reinforced polymer) and threading as OEM caps. The main difference is branding, not performance or durability.