5 things I never do as a built-in oven expert

The Which? cooking appliances expert explains how to get the very best out of your oven by making a few simple changes

Best Buy ovens are pretty much foolproof. They heat quickly and evenly, roast scrummy food, and some even select their own cooking programmes.

But there are still some jobs you need to do to keep an excellent oven working perfectly.

Here are my top five mistakes to avoid if you really want to get the most from your oven.

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1. I never let my oven get too dirty 

This has nothing to do with vanity. Well, not much, anyway. 

There’s a growing consensus that gas hob cooking contributes to kitchen air pollution, but this problem isn’t limited to frying and boiling. Ovens are partly responsible, too, according to research which shows that cooking at high temperatures releases fine particulate matter and volatile organic compounds (VOCs) into the air. 

There’s no need to panic and start eating raw food though. Instead, make sure you clean your oven regularly to reduce burnt food residue, crack open a window when cooking, or use a cooker hood or extractor fan to help clear the air.

If your oven has a self-cleaning function, use it mindfully. Studies show that indoor air pollution is at its highest during pyrolytic self-cleaning, which burns off food residue at temperatures in excess of 400°C.

We’re not saying you should avoid the pyrolytic mode on your expensive built-in oven. But do wipe out as much residue as possible before setting it to self-clean. You should also open the windows or switch on the cooker hood, and close the kitchen door.

I’ve found that steam cleaning my oven every month or so reduces the build-up of burnt bits. You can do this even if your oven doesn’t have a steam clean mode: just heat a roasting tin of water inside for half an hour, and most of the bits should wipe away easily.

It’s not just a problem for London. Government statistics for 2024-2025 show that 'cooking appliances were the largest specified ignition category for accidental dwelling fires, accounting for 44% of these fires.'

My partner thinks everything I cook smells like rotten fish. I’m not sure if this is her problem or mine, but I try to keep the house fug-free by keeping the oven clean.

Find out more about how self-cleaning ovens work

2. I never trust the temperature settings

Maintaining a consistent, even heat is crucial for good cooking and baking. Overheating or underheating something sensitive like a sponge cake can make a huge difference to how edible it is.

Our nine worst-rated ovens all scored poorly when it came to supplying heat, and all failed our cake baking tests, producing 'disastrous' or 'terrible' sponges.

If you’re looking for a new oven, join Which? to find a Best Buy. If you’re happy or stuck with an old one that you suspect might be inaccurate, try the sugar test. Granulated sugar melts at around 185°C - test some in your oven, first at 180°C then at 190°C and compare the results. Or for accuracy, use an oven thermometer.

I’ve figured out that my oven runs about 5°C too hot, so I can adjust the cooking temperature accordingly.

Use our oven temperature conversion table to compare gas, Celsius, Fahrenheit and fan temperatures

3. I never routinely preheat my oven

Here’s a great big caveat for starters: you really do need to preheat your oven for some dishes, including cakes, souffles, cookies and anything else that needs to rise first and then set.

But with multiple heating elements and fans, the best modern ovens heat so quickly (under five minutes to 180°C), that it’s not always necessary. 

For example, some brands such as Miele advise you not to preheat for most dishes, and adjust their suggested cooking times accordingly.

It’s not likely to save a great deal of energy, but I do appreciate not having to go back to the oven a second time to put the food in.

Find out which built-in oven brands are the most reliable

4. I never use the middle shelf exclusively

Recipe books often tell you to use the middle shelf, but in truth it depends what you’re cooking.

If it’s pizza, for example, you want the bottom shelf, ideally with heat from below but assisted by the fan. That should give you a nice, crispy base without scorching the toppings. Roasts, meanwhile, should go slap bang in the middle to ensure they get good heat all round.

We test batches of shortbread our lab, and the results show clear differences between the top and bottom levels in almost all ovens.

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5. I never rest anything on the oven door

It happens very rarely, but oven doors can shatter, something that our members have been reporting to us since 2017. This is understandably very distressing when it happens, and something we all want to avoid.

Oven doors are made of tempered glass, which is specially treated to resist heat and impact. It’s still glass though, and if it does fail it tends to shatter into small, albeit blunt, pieces.

Some of the main causes are a previous physical impact, aggressive cleaning or sudden temperature change, which you can trigger by resting a hot pan on the oven door.

It’s really tempting to put a heavy pan down there when it’s hot out of the oven, but it can cause unseen damage that can later cause the glass to fail.

Faulty product? Here's how to get a refund, repair or replacement