Where Car Spa's customers come from — and how the trade area has tightened

Findings

In short: Car Spa #18 has become a steadily more local business. The typical new customer lived 5.5 miles away in the 2012–2018 era; today it is 3.8 miles, and the wash’s own ZIP now supplies roughly 1 in 5 new reviewers — up from 8%.

• The catchment contracted for a decade straight. Median customer distance fell from 5.5 mi (2012–2018 cohorts) to 5.2 mi (2019–2022), 3.9 mi (2023–2024) and 3.8 mi (2025–2026). The share of customers living within 5 miles rose from 42% to 61% over the same period.
• Home ZIP concentration more than doubled. ZIP 75093’s share of inferred customers grew from 8% of the 2012–2018 cohorts to ~20% of 2025–2026, with 75024 (north Plano) second at 14% — while the wash’s overall review velocity held or rose, meaning the wash is winning more of its immediate neighborhood even as its long-distance draw fades.
• Preston Rd is a hard boundary. ZIP 75075, directly across the street, contributes ~2% of inferred customers all-time. The customer base comes overwhelmingly from the west (75093, 75287, 75252) and north (75024) — consistent with retail gravity following the Market Street / Willow Bend side of the corridor.
• The contraction matches the market’s saturation timeline. As express tunnels filled the 3–5 mile ring (12 active within 5 mi by 2026), customers at the periphery gained closer options. A shrinking catchment radius is exactly the mechanical signature of competitive absorption that the WashIndex saturation model (2.8× in 75093) predicts.

This is evidence of trade-area dynamics, not a statement of the wash’s financial performance. Findings should be read alongside the full WashIndex site diligence for this corner.

Method & caveats

All 1,627 public Google reviews of Car Spa #18 were collected, and the public review history of every reviewer — the complete census, no sampling — was then collected (up to 100 reviews each; up to 500 for reviewers with more than 100), with each reviewed place’s coordinates and category. A reviewer’s home area (model v3) is the center of the densest cluster of their non-travel reviews within 100 miles of the wash: every reviewed place counts equally — high-frequency categories like restaurants scatter around home in all directions, so the cluster center tracks residence rather than any single store choice — the neighborhood holding the most points wins, and the median of that cluster is the home estimate (minimum 3 usable points), snapped to the nearest ZIP centroid. For the neighborhood map view, each inferred home is additionally assigned to its 2023 census tract, and each tract is labeled with the neighborhood name residents actually use — the platted subdivision (city and county GIS layers, phase/section suffixes merged), Zillow neighborhood, or OpenStreetMap place with the largest weighted overlap. Reviews of Car Spa itself and of its own pad are excluded from the inference — using the subject wash to locate its reviewers would be circular. The year a reviewer first reviewed the wash defines their cohort — the point in time they were verifiably a customer.

• Reviewers are a biased sample of customers — Local Guides are overrepresented, unlimited members who never review are invisible, and 33% of reviewers had too little public history to infer a home.
• Old cohorts are inferred from present-day histories. People move; heavy reviewers’ histories skew recent. Early-era spread is therefore noisier than recent eras — the direction of the trend survives this, but quote the recent eras with more confidence.
• Google’s relative review dates get coarser with age, so cohort-year assignment is fuzzier before ~2020.
• All data is public; all outputs are aggregates. No reviewer identities are stored or shown.