Checking engine oil - cold or hot??

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M.A.94

Active Member
Joined
Mar 2, 2016
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307
Location
Newcastle upon Tyne
Car
2001 Mercedes E320 CDI (W210) OM613
I've just serviced my 210 (first time doing it). I was just curious what's more accurate checking engine oil level cold or hot?
 
COLD =when all the engine oil has drained back into the sump and is cold is one way.
HOT = with the engine oil expanded and block are up to temperature and then given 5 minutes to drain back into the sump is the other. Imho HOT is a slightly more accurate reflection of the oil status when hot= under normal engine operating conditions and is thus better. That said there are usually two marks on the dipstick to take account of this- so either will do. Many garages tend to overfill on oil changes. If the oil level is at the hot/max level when the engine is stone cold its overfilled. I like to see an oil level of around 80% +when the engine is fully warmed up.
 
COLD =when all the engine oil has drained back into the sump and is cold is one way.
HOT = with the engine oil expanded and block are up to temperature and then given 5 minutes to drain back into the sump is the other. Imho HOT is a slightly more accurate reflection of the oil status when hot= under normal engine operating conditions and is thus better. That said there are usually two marks on the dipstick to take account of this- so either will do. Many garages tend to overfill on oil changes. If the oil level is at the hot/max level when the engine is stone cold its overfilled. I like to see an oil level of around 80% +when the engine is fully warmed up.

I did read somewheere that the 320 cdi engines are very sensitive to over filling therefore I didn't brim it right to the max line. Thank you for the detailed :)
 
As grober said.

With the oil at normal working temperature, allow 5 minutes for the oil to drain into the sump.

If measuring using dipstick, oil level should be above the buttom mark but also no higher than the top mark.

Measuring onky when cold does not provide the reassurance that the oil won't go above the Max mark when hot.
 
I always check the level cold with the dipstick after being left overnight. Being in the garage I know the car is close to dead level so it's a consistent measurement.

Hot is arguably a more realistic operational check as the level will be higher but it's potentially less consistent in terms of knowing if the oil has drained back to the sump. I don't know if my car has electric level measurement or not. I couldn't be bothered with the fuss of pressing buttons and I wouldn't trust it anyway.

The engine will be fine anywhere between min and max so for me checking the level is a diagnostic to see if the engine is burning oil. It's gratifying when they don't.
 
If you have just changed the oil probably the most important thing to do is run the engine to make sure the filter is primed and then check the level again topping up the oil if necessary.
 
If you have just changed the oil probably the most important thing to do is run the engine to make sure the filter is primed and then check the level again topping up the oil if necessary.

Yes I put the oil in. Let the car for a few mins noticed the oil level had totally dropped. I imagine this is due to the oil circulating around the engine. Added more oil after this and all seems well
 
WIS states to check oil level warm, 5min after stopping the engine
 
I've just serviced my 210 (first time doing it). I was just curious what's more accurate checking engine oil level cold or hot?

When I remember :D
 

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