In today’s experiment, we’re testing another old mechanic trick — adding diesel fuel to the engine before an oil change to “flush out carbon and sludge.” A ton of people requested this after the transmission fluid video, so let’s see what happens when we add diesel to the crankcase, idle the engine, and then drain and inspect everything. Here is a link to the Boroscope everyone asks me about - buy it here - 🧪 What We Test in This Video: ✔️ Diesel added to oil before change ✔️ 60-minute controlled idle ✔️ Oil drain comparison ✔️ Sludge and carbon removal ✔️ Oil filter cut open and inspected ✔️ Compression testing ✔️ Oil Pressure Testing ✔️ Analyze and Review ⚠️ Do NOT try this on a nice engine. Diesel thins oil dramatically — this is for experimental/education purposes only. If you want me to test kerosene, Seafoam, engine flush, ATF again, water decarb, or other old-timer tricks, comment below! 🔧 Subscribe for more mechanic myth-busting and real-world engine experiments!