Lycoming vs Continental: When Does Your Engine Need Preheat?

Every winter, piston owners ask the same question: how cold is too cold to start without preheat? The answer depends on who built your engine.

Lycoming and Continental are the two companies that build almost every piston aircraft engine flying in general aviation today. Your airframe might say Cessna, Piper, or Beechcraft on the outside, but the engine under the cowling is almost certainly a Lycoming or a Continental. If you aren't sure which you have, the engine data plate and your aircraft logbooks will tell you.

That distinction matters in winter, because each company publishes its own cold-weather guidance (Continental in Service Information Letter SIL 03-1, Lycoming in Service Instruction SI 1505), and the thresholds are not the same.

TL;DR

Continental recommends preheat when an engine has been exposed to 20°F or below for two hours or more. Lycoming calls for preheat when engine temperature drops below 10°F, or 20°F for -76 series engines. Both warn that cold starts on a cold-soaked engine can congeal oil and cause abnormal wear or engine damage, and both say to start immediately after preheating. In Michigan winters, a night in a heated hangar is the easiest way to stay well inside both limits.

Continental's preheat threshold

Continental's SIL 03-1 calls for preheat when the engine has been exposed to temperatures at or below 20°F for two hours or more.

Continental warns that failing to preheat a cold-soaked engine can congeal oil in the engine, oil hoses, and oil cooler, leading to loss of oil flow, internal damage, and possible engine failure.

It recommends preheating for at least 30 minutes, and says to shut down and repeat the preheat if oil pressure can't be kept between 30 and 100 psi after start.

Lycoming's preheat threshold

Lycoming's SI 1505 calls for preheat when the engine has dropped below 10°F, or 20°F for -76 series engines.

Lycoming warns that improper cold-weather starting can cause abnormal wear, reduced performance, and shortened time between overhauls. It recommends applying heat in 5–10 minute intervals and checking that the engine is holding warmth.

What a proper preheat covers

Both manufacturers want the whole engine warmed, not just the cylinders: oil sump, external oil lines, cylinders, air intake, oil cooler, and oil filter.

Both say to start immediately after preheating, before the engine cools again. In very cold weather, both also recommend external power so the battery isn't doing all the work.

Preheat options: hangar, forced air, or engine-mounted

Heated hangar: warms the entire airplane, including oil, battery, and cabin, and also melts off snow, ice, and frost (heat deicing), so one step handles both problems.
Forced-air preheat: portable heater ducts into the cowling. Good for ramp-parked aircraft.
Engine-mounted heaters: plug-in sump and cylinder heaters. Continental cautions against running them continuously because of corrosion concerns.

Many owners preheat at temperatures above the published thresholds to reduce wear. That is a conservative choice, not a requirement.

Who should take a closer look

Owners of Cessna 172s, 182s, Piper Cherokees and Archers, Bonanzas, and other piston singles and twins that live on a ramp or in an unheated hangar; anyone flying early-morning trips in January and February; and owners who don't know which engine series they have. Check your data plate and logbook before winter.

At Michigan Aviation, our team handles engine preheat and deicing by heat or fluid, plus heated hangar space at KPTK, and as a Cessna and Piper service center, our maintenance team can help if a cold start leaves you with questions.

Frequently Asked Questions

What are Lycoming and Continental?

They are the two main manufacturers of piston aircraft engines in general aviation. Most Cessna, Piper, and Beechcraft piston aircraft are powered by one or the other, and each publishes its own preheat guidance.

How do I know if I have a Lycoming or Continental engine?

Check the engine data plate or your aircraft logbooks, which list the manufacturer and model. The model number also identifies the series, which matters because Lycoming sets a different threshold for its -76 series engines.

At what temperature should I preheat my aircraft engine?

Continental recommends preheat after two or more hours at 20°F or below. Lycoming calls for it below 10°F, or 20°F for -76 series engines.

Why is Lycoming's threshold lower than Continental's?

The manufacturers set thresholds for their own engine designs. Always follow the guidance for your specific engine model.

How long should I preheat my engine?

Continental recommends at least 30 minutes; Lycoming recommends heating in 5–10 minute intervals and confirming the engine retains warmth. Start immediately afterward.

Can I leave an engine heater plugged in all winter?

Continental cautions against continuous use of engine-mounted heaters because of corrosion concerns. Follow your heater and engine manufacturer guidance.

Does a heated hangar count as preheat?

A night in a heated hangar warms the whole engine and airframe, which is the most thorough form of preheat, and it also removes snow and ice without deicing fluid.

Where can I get engine preheat near Detroit?

Michigan Aviation offers engine preheat, deicing by heat or fluid, and heated hangar space at Oakland County International Airport (KPTK) in Waterford, MI.