Engine oil checks: hot or cold?

I've done some searching on here about whether I should check the engine oil when the engine's warm or cold (and by cold, I mean *really* cold: not started for at least, say, 4 hours, preferably 8 hours or overnight). Is there a definitive answer, preferably backed up by Toyota?

I've always checked the oil on my cars when they're stone cold.

Here's some threads where it's been discussed before:

http://www.mkivsupra.net/vbb/showthread.php?t=91697&highlight=check+oil+cold : Kranz (post 3) reckons it should be checked when hot, although I'm pretty sure he's got the effect of a hot engine the wrong way round (i.e. I agree with post 4). Sorry Kranz

http://www.mkivsupra.net/vbb/showthread.php?t=80228&highlight=check+oil+cold. 2 votes for a cold engine, including DB's excellent cross-ref in post 4.

http://www.mkivsupra.net/vbb/showthread.php?t=5507&highlight=check+oil+cold. More cold votes.

http://www.mkivsupra.net/vbb/showthread.php?t=79839&highlight=check+oil+cold.

There's one or two more threads I'm sure. What do you do, and why?

Would be interested to know the answer to this too, if there is one

It's pretty important I think. Several people think that the oil should be checked when the engine's hot, but that just doesn't make logical sense to me. The level on the dipstick isn't in a steady state. It's like someone asking me for my exact location whilst I'm moving. The only steady state that the dipstick level will have is the asymptote that forms when you leave the car's engine off for a long time.

Some people advocate checking the level after 5-10 mins of turning the engine off. I'm not saying this is definitely wrong, but I just want to understand "why 5-10 mins". What happens if I leave it for 20 mins?

Surely the oil in the top of the engine, having been pushed there mainly by the oil pump and possibly a bit by the internal moving parts, will begin to trickle down into the sump as soon as the engine is switched off.

Toyota would have put two lines on the dipstick for hot and cold if it was important.Toyota have two levels on the auto box fluid and power steering I think.

I would say cold. As all oil has drained to the sump, The technical info states the amount of oil that should be in the sump. Although if the engine is hot the oil will run to the sump within a few minutes anyway but the level could be higher due to expansion due to heat.

Oh and make sure you are on a level surface.

anywhere between 1/3 to 1/2 the way up the dipstick when cold, i worry about all soughts of things but when to check the oil level is pretty much a done deal

I cant see it making that much of a difference TBH. So just check when ever i remember or before and after hard days.

Hot engine, give it 10 mins for the oil to drain back down into the sump then check.

I would say cold. As all oil has drained to the sump, The technical info states the amount of oil that should be in the sump. Although if the engine is hot the oil will run to the sump within a few minutes anyway but the level could be higher due to expansion due to heat.

Oh and make sure you are on a level surface.

anywhere between 1/3 to 1/2 the way up the dipstick when cold, i worry about all soughts of things but when to check the oil level is pretty a much a done deal

Hot engine, give it 10 mins for the oil to drain back down into the sump then check.

Oh well

you aren't going to get a definitive answer just lots of to and fro

i agree with Pig that it doesn't make a huge difference anyway, just regularly check it

Oh well

at 1/2 way on the dip stick it simply doesn't matter whether its hot or cold, if it did Mr T would give specific instructions on how to check as per the auto box oil level check

you aren't going to get a definitive answer just lots of to and fro

 

i agree with Pig that it doesn't make a huge difference anyway, just regularly check it

Pigs on his fourth engine though:D:p But thats not down to oil just bad luck/judgement.

In engine development we always had hot oil (90 degrees) set the engine to No1 TDC and wait 5 minutes before checking oil level, then top up with hot oil to top mark.

Cold oil level is normally a couple of mm below hot at the top mark.

Don't think it makes that much difference though, as long as its not too high (causes oil leaks) or too low (bearing damage when cornering).

Pigs on his fourth engine though:D:p

im on my original:p

When i check mercs you can call up oil temperatures on diag machine, id say between 30 and 80(i never see more or less) i have seen about a 2mm change on dipstick

im on my original:p

 

When i check mercs you can call up oil temperatures on diag machine, id say between 30 and 80(i never see more or less) i have seen about a 2mm change on dipstick

Realtime data must be a godsend for checking oil.. Well worth the £££'s for diag setup. I'm joking, at the end of the day if you have low oil or oil pressure probs you have two lights to tell you.

In the army we have a first parade and a during use parade,

so we do cold first then a hot once you have stopped.

We do this on Tanks and CVR(T)'s and there is always a difference

evne on our landrover's and daf trucks

When cold.

Toyota (other manufacturers too) when deciding on such things should realise that the vast majority of people without looking at a manual would check the oil level when cold, so the levels on the dipstick should be marked accordingly.