Amsoil Beat Pennzoil, Kirkland Edged SuperTech: 5W-30 Tests

Every quart of 5W-30 synthetic oil on the shelf claims better wear protection, cleaner engine internals, and longer service intervals, whether it costs 5 dollars a quart or closer to 15. The label rarely tells you anything a lab test could actually confirm, and most drivers end up picking by brand loyalty or whatever is cheapest at the store that week.

Two separate hands-on comparisons put 5W-30 synthetic oils head to head, one pitting a premium brand against another premium brand, and one pitting two budget house brands against each other. Together they cover four real oils across the price spectrum.

What the testing showed

The figures below come from two of Project Farm's independent oil comparisons, each a direct one-on-one playoff between two 5W-30 synthetic oils. The full breakdowns are on the Amsoil vs Pennzoil 5W-30 test and the Kirkland Signature vs SuperTech 5W-30 test.

Amsoil beat Pennzoil in the premium matchup

Amsoil Signature Series, a full synthetic 5W-30, was declared the winner in a direct playoff against Pennzoil Ultra Platinum, also a full synthetic 5W-30. The test's own conclusion: "Congratulations to Amsoil on winning the trophy... Amsoil is the best motor oil tested. Its playoff performance, combined with the lab test results, make this an oil that I would trust for an extended oil change interval." That last point matters for anyone considering stretching oil change intervals beyond the standard schedule, since the recommendation was tied specifically to lab results, not just a single performance run.

Kirkland Signature edged SuperTech in the budget matchup

In a separate playoff, Kirkland Signature Full Synthetic SAE 5W-30, the house brand sold through Costco, was named the budget pick over SuperTech Full Synthetic 5W-30, Walmart's house brand. Unlike the Amsoil versus Pennzoil test, no clear outright winner was declared in this comparison; Kirkland's edge was specifically as the recommended value option between the two.

Two separate tests, not one four-way comparison

It is worth being clear that these are two independent one-on-one playoffs, not a single four-way test. Amsoil was never measured directly against Kirkland or SuperTech, and Pennzoil was never measured directly against either budget brand. Each test answers "which of these two wins" rather than ranking all four oils on one scorecard.

Why the tests were structured as playoffs rather than group comparisons

Both tests used a head-to-head playoff format rather than a larger group test, which means each result is a direct answer to a narrower question than a multi-brand comparison would give. That format has a real advantage: a straight one-on-one comparison isolates exactly two variables, easier to trust than a crowded field where a dozen small differences can blur which factor actually mattered. The trade-off is coverage; neither playoff tells you how Amsoil stacks up against Kirkland, or how Pennzoil compares to SuperTech, because those specific matchups were never run.

How to read this for your own purchase

If you are choosing between two premium synthetic 5W-30 oils, Amsoil Signature Series has the stronger tested result, backed by both a direct playoff win and supporting lab data cited in that same test.

If you are choosing between two budget house-brand synthetic oils, Kirkland Signature was the recommended pick over SuperTech in its own head-to-head, though that test did not declare an outright winner the way the Amsoil versus Pennzoil comparison did.

If you are comparing across the price tiers, for example Amsoil against Kirkland, there is no direct tested data for that matchup in this archive; both oils won their respective playoffs against a different specific competitor, and this guide will not manufacture a cross-tier winner that was never tested.

A few rules that apply to any 5W-30 synthetic oil purchase regardless of brand:

• Match the oil to your manufacturer's specification, not just the viscosity grade. 5W-30 covers a wide range of formulations, and some vehicles specify additional certifications beyond the basic grade.
• Extended oil change intervals need lab-backed support, not just a good playoff result. The Amsoil recommendation specifically cited lab test results alongside its performance win before endorsing longer intervals.
• Budget oils can be a reasonable choice. Kirkland's win over SuperTech in the budget tier shows house-brand synthetic oils are being meaningfully compared and differentiated, not treated as interchangeable commodities.
• A playoff format has limits worth remembering. Because each test only compared two oils directly, treat these results as strong evidence within each specific matchup rather than a ranking of all four oils against each other.

Browse the rest of the engine oil and fluids tested this same hands-on way for additives, transmission fluids, and other oils put through comparable head-to-head testing, since the same playoff-style approach shows up across several of those tests too.