Check oil level cold or warm?

[Gomer03]

The owner's manual to my new (to me) 2007 Corvette says to check oil after the car has been turned off - wait five minutes, but no more than 20 minutes - to get an accurate reading. I've been operating my whole adult life on the principle that only a cold reading is truly accurate.

When did the science of dipsticks change?

 

[ryan2022]

I have always waited about 5-10 minutes after the engine has been turned off. This allows the oil to drain back into the pan.

Oil doesnt expand like ATF, so I dont think it would matter much if it was completely cool. Just my thoughts.

 

[lipadj46]

I can only get an accurate reading on the dipstick when cold

 

[Scienceman]

I alwys check it cold.

some cars may have it specified in the owners manuel.

 

[BobFout]

In your case, the dipstick is calibrated for hot oil checks. You'll get a false high reading (slightly) if you check it when cold. It changed years ago for European cars (even my 2003, and even older VWs are this way). This allows you to check the oil level accurately at each fill-up.

 

[beast3300]

Corvettes always had different procedures with draining and filling engine oil. I wouldn't be surprised if you had to do it the way described in the manual to get an accurate reading.

I believe the best time (in general) is to check engine oil after the enigne sat for a good long while. However the engine should be hot when shut off so the engine oil is hot/warm to drain down.

For example: In my Buick, if I check the level and it reads full(sitting overnight). Then start it for 2 mins to move it then shut if off, after an hour it still won't register full.

Same car, if I run it 15 mins and shut it down it will register correctly after about 5 mins.

 

[beast3300]

I might add my favorite time to check is after sitting overnight.

 

[JohnBrowning]

In most applications it does not make a signifacant difference when talking crankcase oil. ATF is a different ball of wax.Most of my applications over the years I found that I could even check the levels with the engine running and it did not make a big deal. At idle you are not moving that muc fluid around. IN fact I can check my Camry 2003 and my 1997 Buick running,hot and cold then shut them down and check 30 minutes latter and not be able to detect any observable difference onthe dipstick as long as I wipe them before checking.

 

[calvinnnnnnnnn]

most important thing is that your car is leveled

 

[Jimmy9190]

I check my oil on a level surface after my truck sits overnight or at least has cooled off for 4 or 5 hours.

 

[bepperb]

"In most applications it does not make a signifacant difference when talking crankcase oil. "

My experience as well.

 

[JHZR2]

I always find it easiest/most convenient to do cold after sitting a long time. I figure that even if calibrated to a hot engine, the error won't be very huge, and if I see a discrepancy, I should watch more often hot or cold.

Ive never really seen a huge consumption in any of our engines - even those with some amount of leaking... so Ive never really been concerned. It is when oil gets too low that we have an issue. Id imagine that even in a "calibrated" dipstick, the design is such that full on a cold dipstick is good enough to provide protection and not be overfilled.

 

[HyperJinx]

When I change the oil in my Vette I always run the engine for a couple of mins(checking for leaks), turn it off, wait about 5 min and then check the level. After about a hour I will check the level again just to be sure. I have noticed only a hairs difference in the 2 readings being that after sitting a while it indicates just slightly more oil in the pan (which makes sense).

 

[KeithKman]

You say you have a Corvette, but don't mention what model. The Z06 and ZR1 (LS7 and LS9) Corvettes have a dry stump system compared to the regular C6 (LS3).

Checking the oil level on a car with a dry stump oil system is different then a regular oil system found on most cars.

I have a dry stump system on my Sea-Doo and checking the oil is done the following way. The motor has to be at operating temperature. Let the motor idle for 30 seconds, and then shut the motor off. Wait another 30 seconds and then check the oil level. I would imagine cars with a dry stump oiling system are done the same way or very similar.

Always make sure the car is level when checking the oil.

 

[HyperJinx]

Originally Posted By: KeithKman
You say you have a Corvette, but don't mention what model. The Z06 and ZR1 (LS7 and LS9) Corvettes have a dry stump system compared to the regular C6 (LS3).


In most car circles, that absence of a unique designation is indicitive of the base model car. I would understand his description to mean he has a 2007 C6 LS-2.

 

[Spykem4e]

In the owner's manual of the 2005 Cadillac CTS, its written to check when warm or hot and I should let couple of minutes after shutting off the engine to let the oil fully return in the pan.

When I check the oil right after fueling the car, There's always 500 ml missing. If I wait 30 minutes after shutting down, I get the reading right. If I check when the engine is cold, sitting overnight, I have maybe 1mm more on the dipstick than hot or warm.

 

[demarpaint]

Originally Posted By: Gomer03
The owner's manual to my new (to me) 2007 Corvette says to check oil after the car has been turned off - wait five minutes, but no more than 20 minutes - to get an accurate reading. I've been operating my whole adult life on the principle that only a cold reading is truly accurate.

When did the science of dipsticks change?


Really! I've done it stone cold, on level ground in the morning for best results. You'd think they'd want the oil checked when it was all in the pan. Seems easy enough too. I always get the best reading in the morning, or after the engine has been off a few hours. But if I owned something that had some special way of checking the oil, I'd do it that way. Or park it on level ground, let it sit over night, and make my own mark. Then confirm accuracy of that mark by checking it a few times over a week time period. If it reads at that mark then I have my own full mark. Odds are it will read to that mark every morning, and if I was OCD enough to do all that I'd use that for my full mark.

 

[mechtech2]

"Wait no more than 20minutes to check your oil"? Why do they say stuff like this?
What do you think will happen?

Consistency is the key. Especially for noting small changes.
An overnight check when the car is parked in it's usual flat spot is a great way - very consistent.

 

[Gomer03]

Thank you for the replies.

It is the base model Corvette with the LS2 engine.

What's interesting is that the manual not only gives you this 15 minute window in which to check, it actually goes so far as to say that cold readings are inaccurate, or words substantially similar to that effect.

 

[ledslinger]

Follow the manufacturers instructions. Specific time windows for checking oil level could be due to oil returning from peripheral oil system locations may raise the oil level. Oil coolers etc.

If you want to check it cold, top it off according to the manufacturers instructions and make a cold reference mark on the dipstick.

As noted, the difference between a full cold and 15 minutes after shutoff, will likely be within the add and full points anyway.