These two get compared constantly because they overlap in price, in hardness range and in the jobs people buy them for. They are not interchangeable, and picking the wrong one usually shows up six months later as a cracked, hardened gasket.
The one-line answer
EPDM if the enemy is weather, ozone, hot water or steam. Neoprene if the enemy is oil, or if you need some flame resistance and some weather resistance at the same time.
Where EPDM wins outright
- Sunlight and ozone. EPDM has a fully saturated polymer backbone, which means there is nothing for ozone to attack. It will sit on a roof for a decade. Neoprene is good here too, but EPDM is the benchmark.
- Steam and hot water. EPDM handles saturated steam where almost nothing else in this price bracket survives. Neoprene degrades.
- Temperature range. −45 °C to +120 °C against neoprene's −35 °C to +100 °C.
- Acids and alkalis, dilute. EPDM is noticeably better.
Where neoprene wins outright
- Oil and grease. This is the decisive one. Mineral oil makes EPDM swell badly — it is rated D, not recommended, and that is not a marginal call. Neoprene is rated B and will do the job for years.
- Flame. Chloroprene is inherently flame retardant because of the chlorine in the polymer. EPDM burns readily. If your part is anywhere near an ignition source and nobody has specified a flame-retardant grade, neoprene is the safer default.
- Refrigerants and mild solvents. Neoprene tolerates a wider range.
The trap
The most common mistake we see is an outdoor part that also sees occasional oil — a machine guard, a pump skirt, an access hatch on a piece of plant. People pick EPDM for the weather, then the oil destroys it. Neoprene is the honest compromise: it is worse than EPDM at weather and worse than nitrile at oil, but it is the only one of the three that is acceptable at both.
The second trap is the reverse: someone picks neoprene for a steam or hot-water gasket because it is "the general-purpose one". It will harden and fail. That job is EPDM's.
Cost
EPDM and neoprene sit close together in our pricing — EPDM around $4.50 per pound, neoprene around $6.75. The gap is real but it is not usually what decides the specification. Choose on chemistry, not on the 30 percent.
What to do next
If you can name the fluid and the temperature, run them through the chemical compatibility chart. If both materials come out acceptable, order a sample pack and test the one that is cheaper for your thickness. If neither comes out acceptable, you are probably looking at nitrile, butyl or FKM instead.