AMSOIL vs Polaris PS-4
Polaris PS-4 is the OEM-branded oil for Ranger, RZR, Sportsman, and General models. Here’s how it compares to AMSOIL’s purpose-built ATV/UTV synthetic, using current official specs and AMSOIL’s own published shear-stability testing.
Alan Williams · AMSOIL Direct Jobber #1243776 · Tomball, TX · 225-441-6397
Official Manufacturer Specifications
Current Spec Sheet Comparison
AMSOIL now sells a direct-match synthetic for each Polaris grade, so this is an apples-to-apples comparison of what each manufacturer currently publishes.
| Spec | AMSOIL 5W-50 / 0W-50 ATV/UTV | Polaris PS-4 / PS-4 Extreme |
|---|---|---|
| Standard grade | 5W-50 | 5W-50 |
| Extreme-duty grade | 0W-50 | 0W-50 |
| Rated temperature range (standard grade) | Not published to the same degree range; positioned as a year-round replacement for both grades | -40°F to 100°F (per official Polaris PDS) |
| Wet-clutch compatible | Yes, no friction modifiers | Yes |
| OEM warranty status | Warranty Secure, backed by AMSOIL Limited Warranty | OEM-branded, factory recommended |
| On-track testing | Used by AMSOIL-sponsored riders in the GNCC Series | Not independently published |
AMSOIL specifically recommends its 5W-50 ATV/UTV oil in place of standard PS-4, and its 0W-50 ATV/UTV oil in place of PS-4 Extreme, matching viscosity grade for grade rather than substituting a different weight.
Tell me your Ranger, RZR, Sportsman, or General model and I’ll confirm the exact AMSOIL grade for it, no upsell.
AMSOIL’s Own Published Shear Test, Dated 2011
What the Shear Stability Data Actually Shows
AMSOIL has published ASTM D-7109 shear stability test results (a recognized industry standard test method for viscosity loss under mechanical stress) comparing its own oil to the earlier Polaris PS-4 Plus formulation. This data is worth knowing, with two honest caveats up front: it’s AMSOIL’s own test, not an independent third-party lab result, and it dates to 2011, testing the older PS-4 Plus 2W-50 product rather than the current 5W-50 PS-4 sold today.
| Test Point | Result (AMSOIL’s Published 2011 Data) |
|---|---|
| Test method | ASTM D-7109, 30 and 90-pass diesel injector shear stability test |
| At 30 passes | Polaris PS-4 Plus had already sheared out of its starting 50-weight grade |
| At 90 passes, Polaris PS-4 Plus | Lost over 33% of its starting viscosity |
| At 90 passes, AMSOIL Formula 4-Stroke (product tested) | Lost under 5% of its starting viscosity |
Polaris has since updated its PS-4 formulation and clearly labels current viscosity grades on the bottle, something the older PS-4 Plus did not do. Whether the current PS-4 formulation shears at the same rate as the version tested in 2011 has not been independently verified, and no current third-party shear test comparing today’s PS-4 to AMSOIL’s current ATV/UTV oil is publicly available. Take the 2011 data for what it demonstrates about AMSOIL’s shear-resistance approach generally, not as a claim about the exact product on shelves today.
Get AMSOIL’s ATV/UTV synthetic at 25% off as a Preferred Customer, matched to your exact Polaris grade.
Where Polaris PS-4 Is a Reasonable Choice
Polaris PS-4 is a legitimate, purpose-built oil, not a corner-cut product. It’s a reasonable choice for:
- Riders still under the factory extended warranty who want zero maintenance-record ambiguity with their dealer
- Owners who prefer buying everything, oil, filter, and gear, in one dealer visit
- Machines already run exclusively on PS-4 where a rider doesn’t want to introduce a different additive package mid-interval
Common Questions
What’s the AMSOIL equivalent to Polaris PS-4?
AMSOIL’s 5W-50 Synthetic ATV/UTV Motor Oil (AUV50) is the direct match for standard PS-4. For PS-4 Extreme, use AMSOIL’s 0W-50 ATV/UTV Motor Oil. Both are formulated specifically for Polaris Ranger, RZR, Sportsman, and General models.
Does switching to AMSOIL void my Polaris warranty?
No. Under the Magnuson-Moss Warranty Act, a manufacturer cannot void your warranty simply for using a different oil brand, provided it meets the required viscosity grade and specification. Keep your receipts and maintenance records as proof of service.
Is AMSOIL safe for a wet clutch?
Yes. AMSOIL’s ATV/UTV oil contains no friction modifiers, so it’s formulated to be wet-clutch compatible, matching PS-4’s own wet-clutch approval.
Can I mix leftover PS-4 with AMSOIL?
AMSOIL is compatible with other synthetic and conventional motor oils, so mixing won’t damage your engine. It will, however, shorten the service life and reduce the performance benefits of the AMSOIL portion of the fill. For best results, drain fully and refill with AMSOIL rather than topping off a mixed fill.
Get the Right Oil for Your Ranger, RZR, or Sportsman
Call and tell me your model and how you ride it, and I’ll tell you the exact AMSOIL grade, straight, no upsell.
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AMSOIL and Polaris are registered trademarks of their respective owners. Lube Oil Sales is an Authorized AMSOIL Independent Dealer (Dealer #1243776). This page contains affiliate links. Polaris specifications sourced from official Polaris product data pages, current as of this publication. AMSOIL specifications sourced from AMSOIL’s official product data. Shear stability data as published by AMSOIL in 2011, tested against the earlier PS-4 Plus formulation. Last updated: July 2026.