Oil Cooler Sizing Calculator

Size an engine or transmission oil cooler based on heat rejection requirements, oil flow, and ambient temperature.

Input Parameters

Results

--
Heat Rejection Needed
BTU/hr
--
Min Cooler Area
sq in
--
Oil Temp Drop
°F
--
Recommended Rows
Note: Engine oil should stay below 250°F for longevity. Transmission fluid above 270°F degrades rapidly. Thermostatically controlled oil coolers prevent overcooling in winter.

Reference

Heat = Flow × ρ_oil × 60 × Cp × ΔT ρ_oil ≈ 7.1 lb/gal, Cp ≈ 0.5 BTU/lb·°F LMTD = (ΔT1 − ΔT2) / ln(ΔT1/ΔT2) Cooler Area = Heat / (U × LMTD) U ≈ 10 BTU/hr·ft²·°F (air-to-oil)