Engine builders need temperature conversion constantly — coolant runs in °F on most dyno sheets but ECTs spec in °C on import platforms, oil temp on a stock gauge is one scale while the data logger is the other, and EGT pyrometers split by region.
Conversion formulas
- °F → °C: (°F − 32) × 5/9
- °C → °F: (°C × 9/5) + 32
- °C → K: °C + 273.15
- K → °C: K − 273.15
The 5/9 ratio (not 1.8 exactly) is what catches people — at high EGT numbers a rounding error compounds fast. 1400 °F is 760 °C, but 760 × 1.8 + 32 = 1400 (works) while 1500 / 1.8 - 32 = 801 (off by 1). Always do the conversion in one direction, don't try to verify by inverting.
Common reference points for engine builders
- Coolant — normal range: 195–220 °F · 90–104 °C
- Coolant — danger zone: 240 °F+ · 116 °C+
- Oil — normal: 220–250 °F · 104–121 °C
- Oil — viscosity breakdown risk: 290 °F+ · 143 °C+
- EGT — diesel safe sustained: < 1250 °F · < 677 °C
- EGT — diesel danger: 1400 °F+ · 760 °C+ (drive pressure rises non-linearly past this)
- EGT — gas N/A safe: < 1550 °F · < 843 °C
- EGT — gas turbo safe: < 1650 °F · < 899 °C
Why builders need this often
Dyno sheets, OEM service manuals, and aftermarket loggers don't agree on units. Mahle and Mahle Motorsport publish ring gap specs at 200 °C for the chrome moly ones, but a US shop might be staring at 392 °F on a part data sheet. A piston coating limit might be 525 °F (273 °C) — but the same supplier in Europe lists it as 270 °C.
The Kelvin column is mostly useful for combustion math (charge air temperature ratios, polytropic compression) since absolute zero matters in those formulas — but for everyday shop work, the °F/°C swap is what gets used 50 times a day.