Your oven works every shift. A few minutes a day keeps it from quitting on the busiest one.

• Clean spills right away. A boil-over baked on for a shift turns into smoke, odor and a fire risk.
• Clear the crumbs. Burnt bits on the floor of the oven smoke and change how food tastes.
• Wipe the inside at close. Once the oven is cool, use a damp towel and the cleaner the manual allows. A well-kept oven often needs only warm, soapy water.
• Wipe the door glass and gasket. Grease on the gasket makes it stiff and stops it sealing.

Racks. Pull them and soak them in hot, soapy water. Scrub off what's left with a brush.

Convection fan. On a convection oven, check that the fan guard is clean and the fan spins freely. Grease on the fan throws it off balance.

Door. Open and close it a few times. It should close firmly and seal on all sides. A door that hangs open lets heat out and makes the oven work harder.

Outside. Wipe the controls and knobs. Grease on a control panel works its way into the electronics.

The dial says 350°F. The oven might be at 325°F, or 375°F. A few degrees off changes cook times and quality.

Put an oven thermometer in the middle of the oven. Set it to a common temperature and let it heat for twenty minutes. Compare the reading to the dial. Check it again with the thermometer on each side.

If the reading is off by more than the manual allows, or one side runs hotter than the other, the thermostat, sensor or burner needs service.

Combi ovens use steam, and steam means scale from hard water. Run the cleaning and descaling cycles the manual calls for. Use the chemicals the maker specifies. A combi that skips its cleaning cycles builds scale in the steam generator, and that's an expensive part.

• Spraying harsh oven cleaner on parts the manual says to avoid, like fans, gaskets and probes.
• Slamming the door, which wears the hinges and gasket.
• Lining the oven floor with foil, which can block airflow and burners.

• It takes longer than it used to to reach temperature.
• Food comes out burnt on one side and raw on the other.
• The fan squeals, rattles or doesn't spin.
• A gas oven won't light, or the pilot keeps going out.
• The oven shuts off mid-service or shows an error code.