The auto-buyer journey is becoming more fragmented and less linear. The ​​​​2026 Urban Science Harris Poll Study* surveyed more than 3,000 US adults who own, lease, or plan to purchase or lease a vehicle within the next 12 months. The study found 31% of auto buyers now prioritize value and price over brand loyalty. And 44% said they spend more time researching before contacting a dealer compared with one year ago. 

The more tools and sources consumers have to help them arrive at their purchase decision, the more opportunities there are for advertising dollars to miss their intended mark. As marketers expand their collective focus across channels and touchpoints, incrementality testing is emerging as a critical framework for understanding which media investments are driving verified sales outcomes and which are allowing wasted spend to quietly accumulate.

Why automotive ad spend keeps going to waste

Automotive marketers face a significant challenge in measuring and optimizing their campaigns: most vehicle purchases still occur offline. This makes it difficult to directly connect digital media exposure to in-dealership sales outcomes.

Connecting media exposure to verified, people-based sales data changes this dynamic. It provides the foundation for causal measurement, allowing marketers to determine whether advertising drove outcomes that would not have occurred otherwise. Without that link, it becomes difficult to separate correlation from true performance.

The financial implications of wasted ad spend are significant. The Association of National Advertisers estimates programmatic media waste reached $26.8 billion in Q2 2025 alone. That waste tends to appear in predictable ways:

• Impressions served to bots
• Retargeting consumers who have already converted
• Broad audiences that include buyers who were never in market
• Audience suppression based on delayed vehicle registration data
• Campaigns optimized with proxy website engagement rather than sales outcomes

In each case, signal distortion obscures which activity is truly driving incremental impact.

What incrementality testing actually does

Incrementality testing helps address this gap by isolating the true impact of media spends. These tests are small, controlled experiments that compare outcomes between exposed and non-exposed audiences to determine whether advertising influenced results.

In automotive, when incrementality testing is backed with industry sales data updated daily, marketers can quickly identify which audiences, channels, and campaign variables led to incremental lift, do more of what works, and shift dollars away from what doesn’t. The alternative measurement method, which uses vehicle registration data, can lag months behind an actual purchase. This delay can leave marketers spending against consumers who have already purchased or left the market, leading to wasted spend and lost opportunities to focus on customers who are still in market.

However, incrementality is not a cure-all. It does not eliminate the sources of wasted ad spend across the ecosystem. Instead, it serves as a diagnostic tool, providing the clarity needed to identify underperforming investment and optimize away from it over time.

Putting incrementality into practice

Adopting incrementality does not require large-scale transformation. Many marketers can start with small, structured tests that build into a repeatable process over time. A practical approach includes:

• Identifying a clear outcome, such as vehicle sales or qualified leads
• Selecting a single journey stage to test
• Creating a control-and-treatment structure using a holdout audience, geography, or time-based split
• Defining a measurement window aligned to the purchase cycle
• Monitoring for diminishing returns, including overlap or saturation
• Reallocating budget toward segments driving incremental lift
• Repeating the process to establish a testing cadence

Many platforms already offer native testing and optimization capabilities. For example, when Mazda North America ran its October 2025 “More to Move You” campaign, they used Urban Science’s solution to securely provide daily offline sales data to Meta, allowing the platform to optimize not just for engagement, but for verified vehicle sales on a daily basis.

Using Meta’s native conversion lift testing, Mazda was able to measure performance against a holdout audience and isolate true incremental impact. The result was a 3.5x return on ad spend and a 64% lower cost per incremental sale when measuring performance using Urban Science’s daily industry sales data compared to their standard campaign approach.

Turning insight into action

Many marketers fear “going dark,” even when they are unsure whether a campaign is truly adding value. In practice, campaigns effectively “go dark” while still running once they stop reaching the right buyers or contributing to outcomes.

Rather than relying on assumptions, marketers can start with small, structured incrementality tests powered by verified daily sales data to understand what is truly working and make more confident investment decisions.

*Urban Science Online Auto-Buyer and Dealer Studies, January 2026. These surveys were conducted by The Harris Poll on behalf of Urban Science among 3,012 US adults aged 18+ who currently own or lease or plan to purchase or lease a new or used vehicle in the next 12 months and 252 US OEM automotive dealers, whose titles were Sales Manager, General Manager, or Principal/VP/Owner.