Why Costco Is Rationing Motor Oil as Prices Nearly Double
Issaquah, Monday, 14 September 2026.
Costco has imposed strict purchase limits on motor oil after prices nearly doubled, driven by Middle East supply chain disruptions and refiners prioritizing high-margin diesel and jet fuel.
Implementation of Purchase Restrictions and Price Adjustments
Warehouse retail giant Costco (NASDAQ: COST) has instituted strict purchase limits on its Kirkland Signature motor oil as commodity and transportation costs continue to escalate [1]. As of 2026-09-12, the price of a 10-quart (9.46-liter) pack of Kirkland Signature full-synthetic SAE 5W-30 motor oil increased to $57.99, up from the previous price of $30.00 [2]. This adjustment represents a price increase of 93.333 percent, nearly doubling the cost for consumers [1][2]. To manage inventory amidst shortages, Costco has implemented a purchase restriction of two cases of motor oil per customer per week [2]. Concurrently, purchases of Mobil 1 six-quart (5.68-liter) cases are capped at five per member, with prices reaching $44 [1][3]. These measures signal potential supply chain friction and persistent inflationary pressures within the automotive after-market sector, impacting consumer spending dynamics [1].
Geopolitical Disruptions and Supply Chain Constraints
The scarcity driving these limits traces back to significant geopolitical instability affecting global lubricant supplies. The U.S. historically imports approximately 44% of its Group III base oils, essential for synthetic motor oil, from three Persian Gulf producers: Bapco (Bahrain), ADNOC (UAE), and Pearl GTL (Qatar) [1]. A major supply chain disruption occurred in March 2026 when Iranian airstrikes damaged the Pearl GTL facility in Qatar, crippling a significant portion of global production for at least one year [1][5]. Global oil supply chains are further constrained by the ongoing military entanglement with Iran and the blockade of the Strait of Hormuz, preventing exports from key Middle Eastern producers [1]. On 2026-09-11, satellite imagery confirmed smoke at Saudi Arabia’s East-West Pipeline, a critical infrastructure point for crude exports outside the Strait of Hormuz [2]. Additionally, reports from 2026-09-11 indicate Iran-aligned Houthis reached the island of Perim in the Bab el-Mandeb Strait, threatening a key global shipping lane [2]. The Pearl GTL facility in Qatar is expected to remain crippled for at least one year following damage sustained in March 2026, though the status of production recovery remains unknown as of 2026-09-11 [1][alert! ‘Status of production recovery unknown; ongoing impact confirmed as of 2026-09-11’].
Refinery Economics and Regulatory Costs
Beyond geopolitical factors, economic incentives are driving refiners to prioritize other products over motor oil base stocks. Refiners are prioritizing the production of fuel, specifically gas and diesel, over motor oil because fuel refining yields higher profit margins [2]. Global refiners are currently prioritizing the production of diesel and jet fuel, which have reached 40-year high profit margins, over the manufacturing of motor oil base oils [5]. Crude oil is currently trading at approximately $100 per barrel, driven by geopolitical conflicts, including the war involving the U.S., Israel, and Iran [2]. As of 2026-09-12, AAA data shows diesel prices reached a record $1.60 per liter ($6.06 per gallon), marking an 8-cent increase from 2026-09-11 [2]. Furthermore, modern engine requirements, such as General Motors’ “Dexos-approved” certification, mandate expensive per-product and per-unit licensing fees, exacerbating retail price pressure [1]. Any vendor wishing to market oil as Dexos-approved must pay two licensing fees: one per product and one per unit sold [3]. These licensing criteria, which once applied only to especially demanding engines, have become the rule rather than the exception [3].
Market Outlook and Consumer Impact
The convergence of supply constraints and regulatory costs suggests sustained pressure on prices for the near future. President Trump stated on 2026-09-09 that oil and gas prices will remain elevated until after the midterm elections in early November 2026 [2]. This prediction regarding the timing of price decreases is currently ongoing [2]. South Korean refiners, typically a secondary supply source, are currently unable to fill the supply gap due to their own difficulty in securing raw crude oil [5]. Consequently, the traditional cost-saving advantage of DIY oil changes is reduced when combined with the cost of a filter [4]. Costco’s own product still undercuts the Mobil 1 alternative, so the value proposition holds, though it is a smaller advantage than shoppers found even a few weeks ago [3]. The purchase limits mean stocking up is no longer an option either, forcing consumers to adapt to more frequent purchasing cycles at higher price points [3].