Question about checking oil

[CARGUY40]

I noticed after i drive and check my oil say an hour later its higher then when i check it the next day dead cold so when is it best to get a accurate reading? I like to check my oil the next day after the car sat over night before i drive it but some say when u turn the engine off check the oil after 10min?

My oil reads dead on the full mark when i check it the next day when its dead cold but if i check it say an hour after i driven it the oil is showing past the full mark.

 

[RiceCake]

I check whenever its lowest. In my case its cold, like you said. I figure its better off filling it a little over full when operating, a half a quart extra isn't a big deal. When the car has been run anyhow the oil level seems to vary; that and the oil still running down the dipstick tube makes my car annoying to check when its been recently run.

The dipstick is pretty general a check; so long as you're not reading none on it, oil is bubbling out the dipstick tube, or its like an inch over the max, it should be golden.

 

[Ibrahim]

I check my car engine oil level when its cold (this has served me well) or I will wait 5 to 15min's if I had just pulled in my drive way.

 

[CARGUY40]

i just think checking it the next day is best so every lil drop of oil has reached the pan since it sat for hours i think checking 10min after driving is not enough time for all of it to reach pan.

 

[VicVinegar]

I forget the exact language, but my manual says to check it a few minutes after running. So I'll usually pull in the garage, walk the dogs, and go back to check the oil and add some if necessary.

 

[Donald]

So a follow-up question. What is the least amount of oil you will add when you are low. (How low before you add oil?) One cup (8 oz) PT (16 oz) QT (32 oz). (I hope no one says "when the light comes on!)

Will you add the remainder of an opened QT, or exactly what is needed?

 

[RiceCake]

Originally Posted By: Donald
So a follow-up question. What is the least amount of oil you will add when you are low. (How low before you add oil?) One cup (8 oz) PT (16 oz) QT (32 oz). (I hope no one says "when the light comes on!)

Will you add the remainder of an opened QT, or exactly what is needed?


I add when the light comes on. Thats what its for.




Okay, kidding, but for me usually when it hits the halfway point thats when I add, its a half quart so its a nice easy measurement. Anything else is odd fractions I don't wanna dawdle around with and any lower I run the risk of it dipping far if I forget to add oil. I don't measure very perfectly. If its at the halfway mark, I dump about half a bottle in. Works a treat.

 

[TFB1]

Oil does expand when hot, so if it's almost completely drained back while the engine is still fairly warm, it's possible to have a higher reading than after it's gotten cold...

Same deal with transmission fluid and why it's supposed to be checked hot, when cold it's possible to get a low reading due to contraction... In a trans it's far more noticeable due to most having 8-12 quarts capacity vs 4-6 of the average oil fill...

I add to mine when it's a full quart low, unless maybe tracking or racing, being down one isn't going to cause any harm...

 

[electrolover]

Originally Posted By: Donald
So a follow-up question. What is the least amount of oil you will add when you are low. (How low before you add oil?) One cup (8 oz) PT (16 oz) QT (32 oz). (I hope no one says "when the light comes on!)

Will you add the remainder of an opened QT, or exactly what is needed?


I add if its a half quart low. Really just being in the middle of the stick is fine, but I like it to be at the top of the mark. So if it will hold a 1/2 without going over I add. If not I dont.

 

[mechtech2]

Dead cold is more consistent than various warm and possibly undrained readings.

 

[The_Jake]

Check in the morning dead cold after it has sat all night and all the oil has drained to the sump.

 

[Clevy]

The oil should always be checked while everything is at operating temp. The fluid a are fully expanded and that would represent where everything is while the engine is in operation.
If it high or low when cold who cares,it's their levels during operation.

 

[SteveSRT8]

Since many cars have differing sumps and levels, no one procedure is best for all of them.

On most vehicles I check it before starting in the AM, as it's very accurate. But on my play car the sump level is only part of the story, you need to check a couple of places to really know what is going on.

For the typical car sold today it is probably best to check it first thing in the AM before starting IMO.

 

[KawasakiGuy]

Good question, but I think this varies from car to car. On my car it always gives the best reading when its cold or sat over night. When it's warm it usually reads way off the chart.

 

[RF Overlord]

As expected, there are 9 responses with 11 different answers.

IMHO, the correct way to check the oil is whatever the owner's manual says. As long you're checking it in a consistent manner every time, and the level is between the add and full marks, it's good.

 

[The_Jake]

Originally Posted By: Clevy
The oil should always be checked while everything is at operating temp. The fluid a are fully expanded and that would represent where everything is while the engine is in operation.
If it high or low when cold who cares,it's their levels during operation.


Do you heat you oil to 200F when you change it to get the proper volume? Do the manufacturers heat it to 200F when they fill the containers? All volume measurements are taken at ambient temperatures.

 

[Kestas]

boostedtsiawd, what does your owners manual say on how to check the oil?

 

[Grebbler]

My turn to stir up the pot.

The issue is second guessing the engineers.

Base requirements: Enough oil in the pan to keep the pickup screen submerged at all times during bumps and hills and driving in circles while not so much that the crank is pounding into the pool of oil.

Checking it cold after an overnight sitting will probably give the most consistent reading. Everything has oozed back to the pan and the filter has emptied as much as it's likely to. Thermal expansion differences between ambient temps of 20F in winter to 80F in summer are small compared to ambient and an operating temp of 200F. Engineer #1 says this is fine and marks the dipstick according to an average thermal expansion of 0.0004 per 1F. The mark will be closer to the tip of the dipstick to take into account the expansion at operating temp and he/she will tell you to check it cold.

Engineer #2 likes to base their work on a hot engine. They know how much clearance they want between the crank and the oil while running. This engineer wants the lifters and the filter filled and takes into account any ADB devices. This engineer assumes most people will check the oil at a gas station after driving or get an oil changed at Jiffy Lube just like he does and will mark dipstick where he wants it at after a 10 minute ooze period. This mark will be further up the dipstick.

Engineer #3, who oversees the other two, may add a fudge factor because he knows that most people that drive cars are idiots and will either use the lowest mark or the highest of the range. He may assume someone will crank their torsion bars up front or put big tires on the back and specify a 1/4 inch deeper pan and screen to allow more clearance.

Variables: Manufacturing tolerances of the oil pan, gasket, dipstick, tube, engine angle (car parked on an incline, worn springs, low tires, and the human error of thinking that, "Gee, I only drove to the gas station. The oil is still cold." but now it's spread throughout the motor and the filter is full.

Bottom line: Follow the manual and hope there are no typos. If the manual is vague then use common sense. Cold (before starting) or 10-15 minutes after shutting the motor off to allow most, if not all, to drain back. If you just started it cold for a minute to move down the driveway... don't bother. Check the oil another time.

I, on the other hand, have to assume that there is enough wriggle room that +/- a pint (or even a quart) spread out over 128 square inches of surface area (8" x 16" oil pan measured at the block) will make little difference.

There. Clear as mud

 

[Garak]

Originally Posted By: Clevy
The oil should always be checked while everything is at operating temp. The fluid a are fully expanded and that would represent where everything is while the engine is in operation.


I check my own vehicles when they're cold, usually before I drive it for the first time in the day. Of course, with the cab fleet, that was impossible. The oil was always checked at operating temperatures, and if it had five minutes to drain down, that was a bonus.

 

[Kestas]

If it's that important, another approach is next time you change the oil, refill to specified capacity, then check it the next day at your favorite time (stone cold in the morning, two minutes after shutdown, or both). Make a note of where the level is, and maintain that point as the full mark.