What Hydraulic Fluid Does a KTI Pump Use? ISO 32, ISO 46, or ATF Explained
KTI's primary recommendation is ISO 22 or ISO 32 hydraulic oil for the standard operating temperature range (+14°F to +120°F). ATF Dexron III is explicitly listed by KTI as acceptable under normal conditions — so ATF is not wrong, just not their first choice. ISO 46 is not in KTI's published table and is thicker than needed. Do not mix fluid types.
KTI's Official Fluid Recommendation
Primary choice: Premium hydraulic oil with anti-wear properties, rust and oxidation inhibitors, foam inhibitors. Brand examples: Chevron Rando HDZ, Mobil DTE 10/20 series, AMSOIL, Shell Tellus.
Acceptable alternative: ATF Dexron III — acceptable under normal conditions.
Extreme cold only: Aviation oils (Valvoline ROYCO, Mobil Aero HF/HFA) for prolonged extreme cold below −20°F.
Do not use: Biodegradable hydraulic fluid (incompatible with standard Buna seals). Never mix fluid types.
KTI's Viscosity Chart by Temperature
| Temperature Range | ISO Viscosity Grade | Notes |
|---|---|---|
| −20°F to +32°F (−29°C to 0°C) | ISO 15 | Thin oil for extreme cold — maintains flow when fluid would otherwise be sluggish |
| +14°F to +120°F (−10°C to +49°C) | ISO 22, ISO 32, or ATF | Standard range covering most trailers in most climates including Michigan winters. This is what the vast majority of KTI-equipped trailers should run. |
ISO 46 is thicker than KTI recommends for any trailer application in their published temperature range. It's used in industrial systems at higher sustained temperatures. Using ISO 46 won't cause immediate damage but will make gravity down slower — especially in cold weather — and is thicker than KTI designed the system for. Stick to ISO 22 or ISO 32.
About ATF — Why People Think It's the Right Fluid
- ATF is red. Many trailers have red fluid in the reservoir. People assume red = correct. Proper hydraulic oil is amber or clear — red fluid means someone put ATF in, which KTI allows.
- KTI explicitly permits it. ATF Dexron III is right on KTI's official fluid page for the standard temperature range. It's not a hack.
- The viscosity is compatible. ATF sits in approximately the same range as ISO 22–32, which is why KTI includes it on the same row of their temperature table.
- It's widely available. In an emergency fill situation, ATF is the right call over running the pump low.
That said — KTI's first choice is dedicated hydraulic oil. It has better long-term stability and won't foam as readily under repeated cycling. Use ISO 22 or ISO 32 for fresh fills and changes. Use ATF if that's what you have for a top-off.
The One Rule That Overrides Everything
Do not mix fluid types. If your reservoir currently has ATF and you want to switch to hydraulic oil, drain and flush completely first. Mixing ATF and hydraulic oil risks foam, sludge, and additive incompatibility, which will fail valves faster than almost anything else.
