This study examined how petroleum products (petrol, kerosene, and diesel) affect the strength of concrete made with lateritic sand and quarry dust. A 1:1½:3 mix with a 0.65 water–cement ratio and 25% lateritic sand plus 75% quarry dust was used. Thirty-nine 100 mm cubes were water-cured for 7–28 days, then immersed in petroleum products for 30–60 days. Water-cured cubes showed steady strength gains up to 15.74 N/mm² at 28 days. In contrast, exposure to petroleum products reduced strength: after 30 days, averages were 12.89 N/mm² (petrol), 11.36 N/mm² (kerosene), and 13.30 N/mm² (diesel); after 45 days, 12.78, 14.19, and 13.53 N/mm² respectively. Petrol caused the greatest deterioration, kerosene moderate, and diesel the least. Petroleum exposure disrupted cement hydration, increased porosity, and weakened the paste–aggregate bond, reducing durability. The study recommends protective coatings, improved mix designs, and strict management in fuel-contaminated environments such as filling stations and garages.