I was always told to take the oil level on a cold engine, the email from Mazda this morning ‘Looking after your Mazda during lockdown’ says to warm it to operating temperature (for around 10 minutes) before taking the level.
Have I been doing it wrong for 40 years?
Online manual says:
- Warm up the engine to normal operating temperature.
- Turn it off and wait at least 5 minutes for the oil to return to the sump.
But I have almost always done it cold so I guess we are both wrong 
I guess it is to do with how much oil drains down back to the sump long term.
The important level is when it is hot and working.
Measurement conditions need to take account of the engine being off and how long to allow for drain-down, and Mazda have specified their version of how to do it.
But like you both I’ve always done it on a cold engine, usually before setting off on a long journey. Three of us wrong…
Make that 4.
NB handbook says warm, I try and do it then but it’s usually easier to do it cold. I imagine the margin for enough and not enough is quite high so it’s probably not that critical in reality. I know it’s a bad habit but so hard was it to read the black (diesel car) oil on the black dipstick of a recent car I just waited for the oil light to come on and then top it up, making sure there was always a bottle in the boot just in case!
Mazda have always said to check it warm, usually after a 5 minute stand too… do you not read your Owner’s Manuals😉
Like many of you, and 47 years of driving is now fast approaching, I too have always done this when the engine is cold. All my engines, touch wood, have survived, so maybe we should all carry on just doing what we are comfortable with? 
There’s a manual…? 
I’ve not had mine warm for weeks.
That may well be the case at a service, very handy, and almost perfect timing for bringing it into the workshop from the car park to do a check. However it is much more likely to be going straight onto the lift and setting up to drain for a change with a standard n-litres refill.
Unfortunately it is not all that practical in daily life.
You drive to work or going out or home; are you going to wait five minutes by the car to read the oil? No. Usually you go inside, late for meeting or whatever or drop shopping and have a cup of tea. Then remember the car is cold again, and it’s begun to rain, “what a pity, never mind”.
Most convenient is when you know its going to be a long journey.
And being sensible you choose a suitable time in the dry before setting out to check other things as well; tyres, washer fluid, radiator, steering and brake fluids, brake lights as well as the others, and of course the engine oil. All cold, all done in just a few minutes, mostly a quick glance, except the washer always needs a top-up which is why the refill-bottle was close to hand with the bit of clean kitchen paper for wiping the dipstick.
Cold check is practical for day to day.
Warm check is required mostly after a refill, usually if you don’t know exactly how much to put in and need to run it to make sure it’s everywhere it should be, but not leaking.
But a 1 litre margin is so wide, does it really matter? Cold will do.
The dipstick on my 3.75 is always a bit tight to remove when the engine is cold,
which is when I normally check the oil level, making absolutely sure the level is a
smidgen above the high level mark.
Definitely easier to remove the dipstick when the engine is warm/hot.
Basically the same professional advice for any car. (Unless it’s a real speciality and then follow the guide in the hand book).
Check you have a level some where in between low and high when cold is a must.
Then warm the engine up as the oil will expand to some degree.
Wait some 10 min’s, not really that long.
Then check that the level is at or very close to the upper level mark.
Over filling can do harm as well.
Safe guard your engine and pocket. 
PS, I would strongly urge you not to follow Martins advice!
DO NOT wait for the oil light to come on
this has got to be the worst info I have read for a long time
Check the engine hot or cold but if hot wait for 10 minutes or so too make sure the oil is mostly back in the sump.
Dad always used to check the oil level after he’d used a car, irrespective of what it was, and let it stand for a short while. I’ve always just followed his example and do the same.
Having been taught to drive in the RAF (Landrovers) at St. Athan, we were taught P.O.W.E.R, this stood for Petrol, Oil (cold engine), Water, Electrics, Rubber (tyres). I still do this at least once a week and before long drives.
Lol, I said it was a bad habit, I suspect a lot of people do that though, and I doubt any cars really suffer. The 5 however rarely turns a wheel without an oil and tyre pressure check beforehand.
It wasn’t advice, I said it was a bad habit… And they say confession is good for the soul, I feel better for having confessed to my crime against what was an Audi diesel which is still out there being enjoyed by someone else and now on 1486000 miles
The real question is has anyone actually had an engine blow because they used hot rather than cold or vice versa?
Oils are so fluid these days, even when cold, there are very little drain issues.
Perhaps we could get two members to test, well three members. A hot dipper, a cold dipper and one that nevers dips.
Which engine could blow first…
Martins!! 