Costco Lake Zurich 680 S Rand Rd Costco Gas Prices

Figures use this station's own recorded observations in US dollars per gallon; prices are never converted between currencies or units, and records with a different measurement basis are excluded. Repeated recordings of an unchanged price are counted as checks, not as new price observations, so frequently scraped days do not carry extra weight. Weekday comparisons use one value per local day in the station's timezone and compare weekdays within the same week, so a general rise or fall over time does not create a false pattern; they are published only with at least 8 weeks covering 5+ days each, the weekday present in at least 6 of them, and a difference that survives a resampling check over whole weeks. An outlook is published only when a simple trend model beats an unchanged-price baseline on at least 30 rolling chronological holdout forecasts, each scored against a real later observation within 12 hours of the horizon. Missing observations are never filled in.