That’s why AMSOIL says it reformulated Signature Series to specifically target three failure points that matter most in real-world driving: oil volatility (burn-off) under sustained heat, low-speed pre-ignition (LSPI) damage in direct-injection engines, and piston deposit buildup over long service intervals. AMSOIL Signature Series reformulated
The Test Numbers Behind the Upgrade
AMSOIL publishes the following third-party and industry-standard test results for the reformulated oil directly on its product pages:
| Protection Area | Reformulated Signature Series Result | Measured Against |
|---|---|---|
| Volatility (oil burn-off) | 2X better protection | API SQ volatility limits |
| LSPI piston protection (after 25,000 miles) | 4X more protection | Industry LSPI standards |
| Piston deposits (Sequence IIIH test) | 72% more protection | Minimum passing requirement |
| Oil screen plugging (125,000-mile field test, 2025 Ford F-150 Raptor) | 0% plugging | N/A — field study result |
That last figure comes from a 125,000-mile (approx. 201,200 km) accumulation study AMSOIL ran using a 2025 Ford F-150 Raptor as the test vehicle — worth noting that this describes AMSOIL’s own independent field testing, not an endorsement from the vehicle manufacturer.
Which Viscosity Grades Got the Update
AMSOIL and industry trade press covering the announcement report that all eight Signature Series gasoline motor oil grades are affected by the reformulation:
- 0W-16
- 0W-20
- 5W-20
- 0W-30
- 5W-30
- 10W-30
- 0W-40
- 5W-50
AMSOIL has said the new formula is rolling out as existing inventory of the prior formulation sells through, so both versions may be in circulation for a while — see RunAroundTech’s coverage of the announcement and additional trade coverage from Engine Builder Magazine for more background.
Why the Timing Matters: Peak Heat and Towing Season
This upgrade lands right as summer heat and towing put extra strain on engine oil. A late-July 2026 report from The Auto Channel notes that once road and ambient temperatures climb past roughly 38°C (100°F), breakdown risk on hot pavement rises sharply, and cites NHTSA data attributing more than 11,000 tire-related crashes a year partly to heat-related component stress (The Auto Channel, July 28, 2026). Engine oil isn’t exempt from that stress — sustained underhood heat is exactly what accelerates volatility loss and deposit formation, the two areas AMSOIL specifically targeted in this reformulation.
If you’re towing a trailer, hauling equipment, or just driving a lot of highway miles in the heat this month, that’s precisely the kind of severe-service driving where oil quality matters most.
Recommended Service Intervals
AMSOIL publishes two intervals for Signature Series depending on how the vehicle is used:
| Service Type | Interval |
|---|---|
| Normal service (personal vehicle, no severe conditions) | Up to 25,000 miles (approx. 40,200 km), 700 hours of operation, or one year — whichever comes first |
| Severe service (towing, hauling, plowing, excessive idling, dusty conditions, or commercial/fleet use) | Up to 15,000 miles (approx. 24,140 km), 700 hours of operation, or one year — whichever comes first |
Source: AMSOIL’s official oil change interval guidance.
If you tow regularly, that severe-service interval — not the 25,000-mile number — is the one that applies to you. Always confirm the correct interval and any oil-switch decision against your vehicle’s owner’s manual, or give us a call first, especially if your vehicle is still under a manufacturer warranty.
Getting the New Formula
We’re an independent AMSOIL dealer, not AMSOIL corporate, and we work with AMSOIL’s distribution network across the US and Canada — 13 warehouses in total — to help make sure customers can get current inventory rather than whatever’s been sitting on a shelf. If you want to know whether a specific product code has already switched to the reformulated batch, that’s an easy thing to check before you order.
Ready to switch to the reformulated Signature Series before your next oil change, or just want to confirm which formula and interval fits your vehicle? Call us, text us, or order online and we’ll help you get the right grade for your engine and driving conditions.