AIBU to not understand why the oven takes longer than the instructions state?

[BerryCheesecake]

Is it just me?!

Every oven I've ever had doesn't seen to run to time correctly.

I heat the oven up beforehand to the required temperature, and put the food in. After the required time on the packet, I check the food. It's never cooked
I usually give things about another 10mins and the they're cooked. Am I the only one this happens to?

If not, what am I doing wrong?!

Every oven varies.
My new oven cooks faster than the old so we have to keep an eye on things or lower the temp dial abit.

Have you thought about tweeking the temp dail up a wee bit?

Me too. I usually add 15mins to cake recipes. I have an oven thermometer but it's so covered in burnt grease I can't read it it seems to register the correct temp

Many of the people who write these recipes are professional chefs. They use professional standard ovens which are cleaned to a high standard every day. Very clean ovens will be much more efficient than my manky oven the average oven. Also the oven will need to be pre-heated. Professional cooks who write these recipes will think of a pre-heated oven as something that has been on all day to cook other dishes. We probably think of that as an oven that has been on for five minutes .

Do you have an oven thermometer? It could just not be getting hot enough. We recently had to have our thermostat replaced as the temp was totally wrong

I have a light on the front that turns off when the oven reaches temperature! :)

Mine cooks faster.

Are you my DH? When we had our old cooker he used to always be peering at obviously half-raw food saying "but it SAYS 17 minutes on the packet..."

My new oven does it quicker though.

Familiarity is the key. Each appliance and bit of equipment is different.

But taste and touch will always tell you better than any supposed cooking time no matter what the dish.

Ours takes ages :(

Ours too. i always have to put ours on at higher temp than the packet says and leave it for 10 minutes longer. Drives me mad having to do mental arithmetic every time.

really, adding 10 mins to the time on the packet taxes you that much? You could use a calculator.

So, Daughteroflilith, my new oven cooks quicker because its cleaner?
Yup can see that
Though the fan assist may also help

I have to put mine on at a lower temp or it burns everything, whilst leaving the insides raw.

Though i suspect Sparks1 has it right
The more you use equipment the more familiar you are with its foibles.
for example I know by the sound of the engine when to change gear in my van, but the newly aquired car, well still getting used to that

My seal is old and broken and I can't be arsed to repair it.

mine does too

My oven always takes the correct amount of time

My oven is faster than normal. I have stolen some of your oven's pixies

Not sure if the cleaning thing makes much difference tbh, my oven is a a fan oven which I only bought brand new 9 months ago. Had the oven man in to clean it last week and although it is not sparkling and shiny, it still seems slow!

Now not not*

All ovens are different the last 3 houses I've lived in have all had different ovens and they've all taken different lengths of time to cook the same thing.
My electric oven had to have 20/30 mins added to times, my fan assist oven had to have 10 mins taken off of times and my gas oven is more or less right. None of them have ever been very clean so I can't comment on how that effects efficiency :)

My fan oven works fine as long as I set it at normal oven temp and not the suggested reduced temp for fan ovens.

What is annoying though is my brand new microwave which is 1000W and takes longer than my old 650W one! So much for inverter tech +not needing a turntable...

They all vary - I'm so looking forward to moving out of rental properties to my own home with a decent oven and not playing roulette with the baking. I read a good article recently, I think in the Guardian, that said that recipes were guidelines rather than to be followed exactly and every cook should be amending things to suit them, their kitchen, etc Which is lucky, because I usually use cookbooks as something to read before bed and get ideas from rather than to follow- mainly because I'm never organised enough to buy ingredients beforehand so have to improvise

"Many of the people who write these recipes are professional chefs."

But the OP is referring to instructions on packets. Those are usually put together by food scientists who test the product several times in domestic ovens (standard, fan & gas). Their definition of a pre-heated oven is one that has reached the temp specified on the instructions, not one that has been on all day.

OP, even though your oven dial is set on X temp, it doesn't mean the oven is actually at this temp. The only way to check is to use oven temp probes which measure the actual temp. I have seen ovens that vary by 30oC.
Each time you open the oven door you also lose a significant amount of heat.
Then as other people mention, door seals may be damaged or in my case, the oven is hotter on the left so half way through baking, I have to turn a cake in order to get it to cook evenly.
As Sparks says, get to know your oven & you can then adjust accordingly, which it sounds like you're already doing.

I don't even look at how long it takes on the packet. Goes into a reheated oven, packet or homemade, and comes out when it smells cooked. I haven't timed anything for years - except perhaps a souffle or biscuits, small cakes.