Picking the right fuel line size for a 500 horsepower engine? Yeah, that's a big deal. Get it wrong and you're looking at performance problems or worse—safety issues. For a naturally aspirated gas engine, a -6 AN (3/8 inch inner diameter) line usually gets the job done. But if you've got forced induction—turbo or supercharger—or you're running E85, you really ought to step up to a -8 AN (1/2 inch inner diameter) line. That extra room keeps fuel volume and pressure where they need to be. Let's break it all down so you don't screw this up. Honestly? The go-to answer for a 500 hp gas engine is a -6 AN line—that's 3/8 inch inner diameter (9.5 mm). It'll safely handle up to 600 hp on a naturally aspirated setup running pump gas. But here's the thing—boosted engines or E85 change the game. For those, a -8 AN line (1/2 inch inner diameter) is what you want. It can support up to 800 hp on gasoline and gives you a much safer margin with E85 since that stuff has lower energy density per gallon. Don't cheap out. So what actually matters here? A few things. Fuel type, fuel system pressure, and whether you're forcing air in. E85 is thirsty—it needs about 30% more fuel volume than gasoline because it's got less energy per drop. That means a -6 AN line good for 500 hp on gas? Only about 350 hp on E85. Boosted engines also guzzle more under load, so a -8 AN line gives you breathing room. And don't forget line length—longer runs need bigger diameters or pressure drops will kill you. It's not just about the engine. Technically, yeah, a -6 AN line can flow enough fuel for 500 hp on a boosted gas engine. But you're running right at the edge. No margin for cold starts, hot days, or if you ever want more power. Most tuners and builders will tell you flat out: use a -8 AN line for any forced induction setup targeting 500 hp. It reduces pump load, keeps pressure consistent, and saves headaches at high RPM. And if you're on E85 with a turbo? -8 AN is the absolute minimum. Don't push it. If you're going -8 AN for your 500 hp setup, you need a pump that delivers. A 255 liter per hour (LPH) in-tank pump works for gasoline, but for E85 you'll want a 340 LPH pump. Keep pressure at 43-58 psi (3-4 bar) at the rail. External pumps? Look for ones rated for at least 600 hp to cover line losses. And make sure your pump outlet matches the -8 AN line—usually a -8 AN fitting. Simple enough. "For 500 hp, I always recommend going with -8 AN line even for naturally aspirated gas engines. The cost difference is minimal, and it provides a massive safety margin. Fuel pressure drop is the number one killer of high-performance engines, and larger line virtually eliminates that risk. If you ever upgrade to E85 or add boost, you are already set." — Jake Thompson, High-Performance Engine Builder (15 years experience) "Many enthusiasts underestimate the impact of line length and fittings. A -6 AN line with four 90-degree fittings can lose up to 30% of its flow capacity. For a 500 hp target, always measure your total effective line length and use mandrel bends or -8 AN to compensate. I have seen too many cars lean out at high RPM due to undersized lines." — Maria Santos, Fuel Systems Specialist (10 years experience) No way. -6 AN won't cut it for 500 hp on E85. Because E85 has lower energy density, you need roughly 30% more fuel volume. A -6 AN line only supports around 350 hp on E85. You've got to use a -8 AN line for 500 hp on E85. Period. The big difference is inner diameter: -6 AN is 3/8 inch (9.5 mm), while -8 AN is 1/2 inch (12.7 mm). That extra size means -8 AN flows about 50% more fuel at the same pressure. Also, the fittings are bigger, so you'll need larger pump outlets. It's a step up in every way. Yeah, but be careful. High-quality fuel injection rated rubber hose—like SAE 30R9—can handle 500 hp. But it's more prone to permeation and degradation over time compared to AN PTFE-lined hose. For a permanent build, AN line is way better for durability and pressure handling. Don't half-ass it. Absolutely. Longer lines mean more pressure drop. If your run is over 15 feet, bump up one AN size. A 20-foot -6 AN line will have more pressure loss than a 10-foot one, and that can starve your engine at high demand. For long runs, just go -8 AN even for 500 hp gas engines. Trust me.What size fuel line do I need for 500hp
What is the recommended fuel line size for 500hp?
Fuel Line Size Chart for 500hp
Fuel Line Size
Inner Diameter
Max HP (Gasoline, NA)
Max HP (Gasoline, Boosted)
Max HP (E85)
Recommendation for 500hp
-6 AN
3/8 inch (9.5 mm)
600 hp
450 hp
350 hp
Good for NA gas only
-8 AN
1/2 inch (12.7 mm)
800 hp
650 hp
500 hp
Best for all 500hp setups
-10 AN
5/8 inch (15.9 mm)
1200 hp
900 hp
700 hp
Overkill for 500hp
What factors determine the fuel line size for 500hp?
Can I use a -6 AN fuel line for 500hp with a turbo?
What fuel pump do I need for 500hp with a -8 AN line?
Checklist: Fuel System for 500hp
Expert Insights on Fuel Line Sizing
Frequently Asked Questions
Is -6 AN fuel line enough for 500hp on E85?
What is the difference between -6 AN and -8 AN fuel line?
Can I use rubber hose instead of AN line for 500hp?
Does fuel line length matter for 500hp?
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