Understanding the relationship between trading volume and price movements is crucial for analyzing market dynamics. This study examined the correlation between monthly price changes and monthly volume changes for three major oil companies: Exxon Mobil (XOM), Chevron (CVX) and ConocoPhillips (COP). The monthly price and volume data for the period from January 2020 to May 2025 were analyzed using Pearson's correlation coefficient. The results showed a statistically significant positive correlation between price and volume changes for Exxon Mobil, suggesting that increased trading activity tends to be associated with price increases for this company. However, the correlations for Chevron and ConocoPhillips were not statistically significant during the period under review. A strong positive correlation is also found when looking at the correlation between the monthly price changes of the companies observed. On the other hand, the correlation between the volume changes of the observed companies is only strong and positive for one pair of the analyzed companies, while the other companies show a slightly negative correlation. Major oil companies may have varying short-term price-volume relationships, necessitating further research to understand these dynamics and consider other market factors.