I’m hearing all kinds of things about ethanol in fuel that will destroy a normal rubber fuel line. Should I change the fuel line in my car? I’ve heard that ethanol will even eat the steel fuel line. Is that true? What kind of fuel line should I use?

B.E.

Jeff Smith: Let’s start with what used to be the only fuel line – a simple neoprene rubber that seemed to last forever. Well, those days are gone. With reformulated gasoline almost the rule across the country with dozens of different blends depending upon smog levels and geographic locations, gasoline has undergone a tremendous change in recent years. Essentially now almost all gasolines are blended with 10 percent ethanol as a way to improve the octane rating. Ethanol has received a tremendous amount of attention in terms of how this octane booster affects older fuel systems.

The early aftermarket response to this rubber fuel line degradation was to use braided steel AN hose using a chlorinated polyethylene (CPE)-based material that looks like rubber but was – at least for a short time – resistant to degradation by fuel and oil. Unfortunately, changes in fuel blending eventually began to take its toll on this style of fuel line as well.

You may have noticed that late model cars long ago stopped using rubber-like fuel lines. Mainly this was not for pressure-related issues but instead for emission reasons where rubber fuel line allowed fuel to vaporize through the line and into the atmosphere. Late model EFI cars now all use a fluoroelastomer fuel line that looks plastic but is actually a material called polytetrafluoroethylene – PTFE. This material (first trademarked by DuPont as Teflon) is non-reactive to any common use fuels including methanol and even nitromethane! It also creates a fuel vapor barrier which does not allow the fuel to escape through the lines.

ask-10-01aThis is Tech AFX’s PTFE -6 AN hose and as you can see, it has a decent bend radius, but be careful, you it is relatively easy to kink the hose. All PTFE hose demands brand-specific fittings.

If you park your rubber-fuel-lined hot rod in the garage, it’s possible that your wife has complained about the gasoline smell in the garage and yet you can find no evidence of leaks. The combination of a fuel tank vent and rubber fuel lines are likely the cause of the vapor smell. All new cars for decades have been tested for this type of emissions.

But to get back to your question, the issue is that many people believe that a small amount of ethanol is the cause for all their fuel tank contamination issues, which now because of widely-circulated rumors appears to be all blown out of proportion to the real causes. It is true that ethanol in a high concentrations (like E85) will tend to dry out simple neoprene rubber fuel line from the inside out. This can cause serious fire hazard issues.

We had first-hand experience with a budget stainless-steel braided hose that dramatically failed within four months of installation on our drag race Chevelle test car. This was due to reformulated fuel (with 10 percent ethanol) attacking the rubber line, dying it out, and causing a massive leak when we turned the fuel pump was turned on. Luckily, we caught the leak and replaced all the fuel line before it caused a major fire.

As a result of these failures, this has caused several companies to offer PTFE style performance hose and the special fittings required to use this hose. Companies that now offer this style of hose include Aeroquip, Earl’s, Goodridge, Summit Racing, TechAFX, XRP and a few others. The hose uses a PTFE lining with a stainless steel braid or black plastic outer covering. The specific fittings use a ferrule or sleeve between the hose and the outer covering as the seal.

This PTFE hose is much more expensive than neoprene or CPE-enhanced rubber hose although the specific PTFE-required fittings are often similarly-priced to normal AN versions. One disadvantage to the PTFE hose is that it demands a larger bend radius and will easily kink if bent too severely. There are versions of the PTFE hose that are convoluted to allow tight radii but this tubing is even more expensive.

The advantage of the PTFE hose is that while expensive, short of physical damage it should last the life of the vehicle. So if you have a car that you plan to keep forever, converting to a PTFE fuel hose would be a wise investment. Regardless of what further changes occur to gasoline in the future, it’s safe to assume that a PTFE style fuel line will handle it without a problem.

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Ask Away, fuel lines, Jeff Smith
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Author: Jeff Smith

Jeff Smith has had a passion for cars since he began working at his grandfather's gas station at the age 10. After graduating from Iowa State University with a journalism degree in 1978, he combined his two passions: cars and writing. Smith began writing for Car Craft magazine in 1979 and became editor in 1984. In 1987, he assumed the role of editor for Hot Rod magazine before returning to his first love of writing technical stories. Since 2003, Jeff has held various positions at Car Craft (including editor), has written books on small block Chevy performance, and even cultivated an impressive collection of 1965 and 1966 Chevelles. Now he serves as a regular contributor to OnAllCylinders.