Used Car Retailers: AI Market Discovery Index

Benchmark Summary

CarMax led the Used Car Retailers benchmark in August 2026 with 37.6% valid recommendation coverage, ahead of Carvana's 33.8% coverage by 3.8 percentage points. The largest coverage decline came from Hertz Car Sales, which fell from 11.5% in July 2026 to 6.9% in August 2026, a drop beyond normal month-to-month variation. The largest coverage increase came from Group 1 Automotive, which rose from 2.5% in July 2026 to 7.2% in August 2026.

The month showed mixed movement across the category. Three brands moved beyond normal variation: Group 1 Automotive and Penske Automotive both rose, while Hertz Car Sales declined. The benchmark began with 800 prompt-surface observations in each month and produced 593 qualified observations in July 2026 and 598 in August 2026 after qualification.

Current Benchmark at a Glance

Qualified surface breadth counts the six canonical AI/search surface families with at least one qualified observation: ChatGPT, Copilot, Gemini, Perplexity, AI Overviews, and AI Mode. The benchmark maintained full breadth across both months.

For the strategic interpretation of this benchmark, read CiteWorks Studio's analysis of How AI Search Is Recommending Used Car Retailers

Research Scope and Qualification

The public benchmark is narrower than the raw collection universe by design. The funnel below shows how observations were qualified.

Brand-level percentages use the qualified observations as the public denominator, not the raw collection. See the AI Market Discovery Methodology for the complete qualification process.

Current Brand Standings

The table below shows the primary current-month benchmark view, sorted by valid recommendation coverage.

How to Read the Standings

• Presence rate: share of qualified observations where the brand appears at all in the AI answer.
• Valid recommendation coverage: share of qualified observations where the brand receives a clear, actionable recommendation.
• Top-three rate: share of qualified observations where the brand appears in the top three recommended options.
• Rank-one rate: share of qualified observations where the brand is the single top recommendation.
• Net sentiment: positive minus negative sentiment on brand mentions, on a scale from -1 to 1.

For formulas and denominator rules, see AI Market Discovery Metric Definitions.

Recommendation Coverage Movement

Largest Increase: Group 1 Automotive

Group 1 Automotive rose from 2.5% valid recommendation coverage in July 2026 to 7.2% in August 2026, a gain of 4.7 percentage points that moved beyond normal month-to-month variation. The brand's top-three rate moved from 0.0% to 0.2%, while its presence rate rose from 36.9% to 39.8%.

Largest Increase: Penske Automotive

Penske Automotive rose from 4.4% valid recommendation coverage in July 2026 to 8.9% in August 2026, a gain of 4.5 percentage points beyond normal variation. The brand's top-three rate climbed from 3.0% to 8.2%. Its rank-one rate held flat at 0.2%.

Largest Decline: Hertz Car Sales

Hertz Car Sales fell from 11.5% valid recommendation coverage in July 2026 to 6.9% in August 2026, a drop of 4.6 percentage points beyond normal variation. The brand's presence rate declined from 13.2% to 10.7%, though its top-three rate rose from 1.7% to 3.0%.

Category Leader: CarMax

CarMax remained the category leader with 37.6% valid recommendation coverage in August 2026, though the brand's rank-one rate rose to 19.4% even as coverage declined. The gap to second-place Carvana was 3.8 percentage points in August, compared with 3.2 points in July. CarMax retained the highest top-three rate at 30.8%.

Stable Brands

Seven brands moved within normal month-to-month variation. Carvana declined from 38.3% to 33.8% coverage, while Enterprise Car Sales fell from 9.8% to 7.5%, and EchoPark (Sonic Automotive) eased from 8.1% to 7.4%. On the upside, Lithia Motors / Driveway rose from 19.2% to 20.9%, AutoNation edged from 25.0% to 25.6%, and DriveTime held nearly flat from 6.2% to 6.3%.

Recommendation Placement Snapshot

Coverage alone does not show how prominently a brand is recommended. The placement table below shows where leading brands appear within answers.

CarMax's rank-one rate rose from 16.9% in July 2026 to 19.4% in August 2026, even as its overall coverage declined slightly. Carvana's rank-one rate fell from 14.3% to 10.5%. Similar coverage levels can still hide very different first-position rates, as seen in the gap between CarMax's 19.4% and AutoNation's 0.8% rank-one performance.

Buyer-Intent Distribution

The qualified observations in both months fell into the Brand Recommendation class, representing shoppers seeking direct brand suggestions.

The current public series measures only the Brand Recommendation class of discovery and does not yet contain qualified observations in the Pricing & Value or Multi-Brand Comparison classes.

Historical Measurement Record

This is an evergreen benchmark URL. New measurements are added to the same report.

Evidence and Source Layer

The benchmark is built from prompt-level observations that retain the query, AI/search surface, answer, brand outcome, recommendation placement, sentiment, and, where exposed, citations or attributable evidence sources. Source presence is evidence about the information environment. It is not automatically proof that the source caused the recommendation.

Scope Boundaries

This public benchmark does not measure:

• Market share or sales attribution
• Every possible AI response to a given query
• Organic-search ranking positions
• Social media mention volume
• Private or sponsored channels
• Causality from a metric movement alone

About This Benchmark

The LLM Authority Index AI Market Discovery Index tracks how AI systems discover, mention, and recommend brands across the six canonical AI/search surface families. Each monthly measurement captures a snapshot of the AI information environment for a vertical, using consistent qualification rules so results are comparable over time.

• AI Market Discovery Methodology
• AI Market Discovery Metric Definitions
• AI Market Discovery Research Standards
• Modeled AI Authority Value

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