What Hydraulic Fluid Does a Boat Lift Use?
Quick answer
Most oil-filled hydraulic boat lifts take a zinc-free ISO 32 anti-wear hydraulic oil: ShoreMaster fills with Chevron Clarity ISO 32 and Pier Pleasure with CITGO Clarion Green AW-32, while ShoreStation FlexPower lifts use JAX Marine-Guard Blue. Sunstream lifts are the exception: they take only Sunstream's water-based SunFluid, and oil or ATF voids the warranty. Never top up with a generic AW 32: conventional anti-wear oils use metal-containing additives, and Chevron states its ashless Clarity is not compatible with zinc-containing fluids.
On this page
- The fluid each maker specifies
- "Biodegradable" on the label is not what the rules mean
- Why a generic AW 32 is the wrong top-up
- ISO 32, 46 and the cold
- How full the reservoir should be depends on the lift position
- Keeping the fluid clean and dry
- Where this stops applying
- Decision table
- Frequently asked questions
- Sources and further reading
An oil-filled hydraulic boat lift almost always takes a zinc-free (ashless) ISO 32 anti-wear hydraulic oil, and the exact product is printed in the owner's manual. ShoreMaster ships its power units filled with Chevron Clarity ISO 32. Pier Pleasure fills with CITGO Clarion Green AW-32. ShoreStation lists JAX Marine-Guard Blue for its FlexPower lifts. Sunstream is the one major maker that uses no oil at all: its lifts run on a water-based fluid called SunFluid, and nothing else is allowed.
You will hear "any AW 32 hydraulic oil" and "it has to be biodegradable." Both are half right. The grade is usually 32, but the oil is a specific zinc-free type. And the factory fluids are rated only inherently biodegradable, a lower bar than the readily biodegradable that federal rules mean by the word.
- Usual grade: ISO VG 32, about 33 cSt at 104°F (40°C)
- Usual type: ashless (zinc-free) anti-wear oil with low aquatic toxicity
- Exception: Sunstream lifts take only water-based SunFluid; oil, vegetable oil or ATF voids the warranty
- Change interval in the manuals: 2 years (ShoreMaster, Pier Pleasure) to 5 years (ShoreStation, depending on use and condition)
Safety: lower the boat or set the lift's lock pins before opening anything, and never work under a boat held up only by hydraulic pressure. ShoreStation's manual warns that high-pressure oil "easily punctures skin," so check for leaks with a piece of cardboard, never a finger. Dock power circuits are work for a licensed electrician, with the GFCI protection covered in boat lift electrical.
The fluid each maker specifies
These are the fluids written into the makers' own manuals; how the lifts themselves work is in hydraulic boat lifts.
| Maker and lift | Specified fluid | What the maker says about substitutes |
|---|---|---|
| ShoreMaster hydraulic lifts (instructions 1024719) | Chevron Clarity ISO 32 hydraulic fluid | Another maker's fluid must be "equivalent to Chevron Clarity ISO 32"; do not mix fluids |
| Pier Pleasure hydraulic lifts (2020 to present manual) | Clarion Green AW-32 (CITGO) | "Use biodegradable hydraulic fluid"; get the correct fluid from a dealer |
| ShoreStation FlexPower hydraulic lifts (manual 0004549 rev 3) | JAX Marine-Guard Blue Series, listed in ISO 22, 32, 46, 68 and 100 | Contact a ShoreStation dealer "to get the correct type of fluid for your system" |
| Sunstream SunLift and FloatLift | SunFluid, a water-based proprietary fluid | "Use only Sunstream sunfluid, other hydraulic fluids could damage the hydraulic system" |
| Hewitt hydraulic lifts | Hewitt sells a "biodegradable, environmentally friendly hydraulic oil for lifts and pontoon legs" | No ISO grade published on the product page; ask Hewitt for the grade |
| HydroHoist air-chamber lifts | None: tanks are filled with air from a blower | Not applicable (see floating boat lifts) |
None of these manuals lists automatic transmission fluid. Sunstream's dealer FAQ names it, with vegetable oil and ordinary hydraulic fluid, as a substitute that "will void any existing warranty and has the potential to cause major problems to the system."
ShoreStation's manual names five viscosity grades rather than one. One dealer, Boat Lift and Dock, sells JAX Marine Blue AW46 as the fluid ShoreStation includes with its lifts. If you own a FlexPower lift (the range is described in the ShoreStation profile), buy the grade your dealer supplies for your power unit.
"Biodegradable" on the label is not what the rules mean
Pier Pleasure's manual says "Use biodegradable hydraulic fluid," then names Clarion Green AW-32. CITGO's own product guide describes Clarion Green A/W Oils as "inherently biodegradable." ShoreMaster's Chevron Clarity carries the same rating, and Chevron gives the number: 38% degraded after 28 days in the OECD 301D closed bottle test. Chevron counts 20 to 59% as inherently biodegradable, and says Clarity "did not meet the criteria for readily biodegradable, which is degradation of > 60% after 28 days."
The federal definition used for environmentally acceptable lubricants on vessels (40 CFR 1700.3) sets a comparable bar: at least 60% conversion to carbon dioxide or oxygen demand (or 70% carbon removal) within 28 days, for constituents making up at least 90% of the lubricant, plus "minimally-toxic" and "not bioaccumulative" tests. Those rules govern vessels, not docks, but they are the clearest US yardstick.
So what makes the factory oils suitable for a lift over water? Two things, neither of which is biodegradability:
- No zinc. Chevron explains that conventional anti-wear hydraulic oils use metal-containing additives "which can persist in the environment in the event of leaks." CITGO notes zinc compounds are regulated as priority pollutants under the Clean Water Act.
- Low aquatic toxicity. Clarion Green A/W passes the US Coast Guard static sheen test and EPA LC50 tests on mysid shrimp, rainbow trout and fathead minnow. ShoreStation's spec sheet makes the same claims for JAX Marine-Guard Blue, citing the sheen test in 40 CFR Part 435.
A fluid that really is readily biodegradable does exist in the same family: CITGO's Clarion Green Bio, made from high oleic natural esters, is sold as readily biodegradable and as meeting the EPA's 2013 Vessel General Permit requirements for environmentally acceptable lubricants. It is a different chemistry from the Clarion Green A/W that Pier Pleasure fills with. The fluid families and their trade-offs near water are compared in the hydraulic lift maintenance guide.
Why a generic AW 32 is the wrong top-up
AW 32 names a viscosity grade and an anti-wear additive, not a chemistry. Chevron's data sheet says conventional anti-wear hydraulic oils are "formulated with metal-containing performance additives," and it is blunt about mixing those with Clarity: "Clarity Hydraulic Oils AW are not compatible with zinc/calcium containing fluids," and the maker's drain and flush procedures apply when changing over.
CITGO says something different about its own oil: Clarion Green A/W is "compatible with other premium mineral oil-based lubricants." Read the two together and the safe rule is the one ShoreMaster prints: do not mix. If you cannot get the specified fluid, call the dealer rather than guess.
Water-based SunFluid, used across Sunstream's hydraulic lifts, is the extreme case. Sunstream's manual describes it as "water-soluble and safe, and cleans up easily," and the dealer FAQ calls any substitute a warranty breaker.
ISO 32, 46 and the cold
The grade number is the oil's viscosity in centistokes at 40°C (104°F). From Chevron's typical data, Clarity AW 32 runs 33.5 cSt and Clarity AW 46 runs 46.1 cSt at that temperature, so a 46 is about 1.4 times as thick as a 32 on a warm day, and the gap widens as the oil cools. A thicker oil than the pump was set up for makes a lift slower on cold mornings; slow lifts and their other causes are diagnosed in hydraulic lift problems.
| Fluid | Viscosity at 40°C | Viscosity index | Pour point | Biodegradability claim |
|---|---|---|---|---|
| Chevron Clarity Hydraulic Oil AW 32 | 33.5 cSt | 105 | -36°F (-38°C) | Inherently (38% in 28 days, OECD 301D) |
| Chevron Clarity Hydraulic Oil AW 46 | 46.1 cSt | 101 | -33°F (-36°C) | Inherently |
| CITGO Clarion Green A/W 32 | 33.1 cSt | 106 | 0°F (-18°C) | Inherently |
| CITGO Clarion Green Bio 32 | 34 cSt | 223 | -33°F (-36°C) | Readily |
The two factory ISO 32 oils have very different pour points: Clarion Green A/W 32 has a pour point of 0°F, Clarity AW 32 of -36°F. Neither matters while the lift is in use, because Pier Pleasure says not to leave its products in the water during winter months and ShoreMaster recommends storing the hydraulic box indoors over winter. And the ester-based Bio fluid has more than twice the viscosity index, so its thickness changes far less with temperature, an advantage only in a lift whose maker approves the switch.
How full the reservoir should be depends on the lift position
The level in the tank moves as fluid goes into and out of the cylinders, and the makers do not agree on which way. Check the level only in the position your manual names, or you will overfill or underfill.
| Maker | Check in this position | Correct level | When the tank is fullest |
|---|---|---|---|
| ShoreMaster | Fill with the lift completely lowered; check again fully raised | About 1/2 full raised, not less than 1/3 | Fully lowered (level drops as the lift rises) |
| ShoreStation FlexPower | Fully raised | At least 3/4 full | Fully raised |
| Pier Pleasure | Completely lowered | At least 1/4 full, not more than half | Completely raised |
| Sunstream | Cylinders retracted | 1.5 to 2 in from the top | Not stated |
The common mistake is topping up to the brim where the tank is lowest, then watching the excess push out of the cap. ShoreMaster warns that adding oil with the lift anywhere but fully lowered "may cause the reservoir to become over full when the lift is completely lowered."
Keeping the fluid clean and dry
ShoreMaster's manual names dirt, water and trapped air as the contaminants that do the damage, and gives two rules:
- Filter what you add. Pour new oil through a 25-micron filter, or at least a funnel with a 200 mesh or finer screen, clean and dry.
- Check for water after storage. After winter, or whenever condensation is possible, look at the reservoir; if water may have got in, change the oil.
ShoreStation's test is visual: oil that looks "milky" could be contaminated and should be changed by a dealer. Sunstream's FAQ describes healthy SunFluid as "a clear pink-ish color with no visible residue."
Change intervals differ more than the fluids do:
- ShoreMaster: change the oil every two years, by a dealer.
- Pier Pleasure: flush at least once every 24 months. The manual gives an owner procedure: drain and refill the reservoir with the lift lowered, then raise the lift with one hose run into a bucket to push out the old fluid.
- ShoreStation: every 5 years "depending on use and condition," by a qualified dealer.
- Sunstream: an annual dealer inspection that includes the hydraulics; SunFluid level and condition are listed as maintenance items, not warranty items.
Field tip: on Pier Pleasure's flush the open hose whips under pressure, so the manual says to secure it in a bucket or have a helper hold it. Put absorbent pads on the dock first; oil that leaves a sheen on the water is a spill to contain and report. Old oil goes to a recycling center.
Where this stops applying
This covers the fluid in a lift's power unit and cylinders, not the gearbox on a cable lift, which takes a far heavier oil or grease (see what oil goes in a boat lift gearbox). Makers not in the table, such as Golden, Basta and Neptune, were left out because no published fluid specification was found. Older lifts may hold something else, and a label on the reservoir or a dealer's record overrides the ISO 32 default.
If the lift is drifting down or will not hold rather than simply low on fluid, set the lock pins first and read lift slipping or not holding. For the off-season, ShoreStation stores its lifts fully raised with pins installed so the cylinder rods are retracted, while ShoreMaster stores its hydraulic lifts down to protect the rams; the reasoning is in empty boat lift up or down and the rest of the routine in winterizing a boat lift.
Decision table
| Your situation | Use | Why |
|---|---|---|
| ShoreMaster hydraulic lift | Chevron Clarity AW 32, or an equivalent zinc-free ISO 32 | Factory fill; Clarity does not mix with zinc-containing oils |
| Pier Pleasure hydraulic lift | Clarion Green AW-32 from a dealer | Factory fill named in the manual |
| ShoreStation FlexPower lift | JAX Marine-Guard Blue in the grade your dealer supplies | The manual lists five grades |
| Sunstream lift | SunFluid only | Water-based system; oil, vegetable oil or ATF voids the warranty |
| Unknown lift, unlabelled tank | Nothing until you identify it | Wrong family can damage seals; see finding boat lift parts to identify the maker |
| Want a readily biodegradable fluid | Only with the lift maker's written approval and a full flush | Esters are a different chemistry from the factory oil |
Frequently asked questions
Can I use AW 32 hydraulic oil in my boat lift?
Only a zinc-free AW 32 that matches what the maker specifies. ShoreMaster fills with Chevron Clarity ISO 32 and Pier Pleasure with Clarion Green AW-32, both ashless. Conventional anti-wear oils use metal-containing additives, and Chevron states Clarity is not compatible with zinc-containing fluids. Sunstream lifts take no oil at all.
Can I use ATF in a hydraulic boat lift?
None of the lift manuals reviewed here lists automatic transmission fluid. Sunstream's dealer FAQ names ATF, vegetable oil and ordinary hydraulic fluid as substitutes that void the warranty and can cause major problems. On oil-filled lifts, ShoreMaster's rule is not to mix different fluids, so ATF has no place in the reservoir.
Is boat lift hydraulic fluid biodegradable?
Usually not in the strict sense. The factory oils at ShoreMaster and Pier Pleasure are rated only inherently biodegradable: Chevron Clarity degraded 38% in 28 days, short of the 60% that defines readily biodegradable. What suits them to a lift is that they are zinc-free and low in aquatic toxicity.
Sources and further reading
- ShoreMaster, Hydraulic Box installation and operating instructions 1024719: factory fill, mixing, levels, filtering, change interval, storage (https://static.shoremaster.com/instructions/1024719_SMR.pdf)
- ShoreStation, FlexPower Hydraulic Boat Lift Owner's Manual 0004549 rev 3: fluid specification, levels, change interval, storage
- Pier Pleasure, Hydraulic Boat Lift Owner's Manual, 2020 to present: factory fluid, tank levels, flush procedure, winter warning (https://www.pierpleasure.com/wp-content/uploads/2026/03/owners-manual-hydraulic-lifts-2020-present.pdf)
- Sunstream, SunLift SLX manual 660963 rev A (https://quaisolutions.ca/wp-content/uploads/2022/02/SLX-B-manual-660963revA-01.pdf)
- Sunstream, FloatLift FL6012 Assembly, Installation and Use Manual (https://sunstreamboatlifts.com/wp-content/uploads/2014/08/FloatLift%20Assembly,%20Installation%20and%20Use%20Manual%20for%20FL6012.pdf)
- Quai Solutions (Sunstream dealer), FAQ (https://quaisolutions.ca/faqs/?pg=2)
- Chevron, Clarity Hydraulic Oil AW 32, 46, 68, 100 product data sheet (October 2020) (https://petroleumservicecompany.com/content/pdfs/Chevron_Clarity_Hyd_AW_PDS_2022.pdf)
- CITGO, Clarion Food Grade and Environmental Products Guide, 2025 edition (https://www.citgomarketnet.com/MarketNetWebOther/Lubes/ProductInformation/PocketGuides/ClarionPocketGuide.pdf)
- Boat Lift and Dock, JAX Marine Blue Hydraulic Fluid AW46 listing (https://www.boatliftanddock.com/product/5258/jax-marine-blue-hydraulic-fluid-aw46-bio-degradable-1-quart)
- Hewitt, Hydraulic Lifts and Pontoon Leg Oil (1 gallon) product page (https://www.hewittrad.com/p/hydraulic-lifts-pontoon-leg-oil-1-gallon)
- HydroHoist, Side-Tie "B" Model 7500B Installation Manual (https://cdn.shopify.com/s/files/1/0509/5174/9813/files/HydroHoist_Side_Tie_B-_7500_Manual.pdf)
- 40 CFR 1700.3, definitions for environmentally acceptable lubricants (https://www.law.cornell.edu/cfr/text/40/1700.3)