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I've noticed a large difference between hot and cold readings on Acura TL’s Gen 4 (SH-AWD) vehicles, up to 1/2 a quart difference between readings; cold in the morning and few Seconds after shutting a warm engine as per user manual.
Our dipsticks are calibrated for reading a few seconds after warm engine shutdown, when cold in the morning, reading can show up to a half quart low.
The reason behind this is the oil expansion factor, 4.5 QTY at 200 degree oil takes up more volume than 4.5 QTY at 40 degrees; which indeed can vary up to half a QTY.
Driving with too much oil in your engine is as bad as having to little.
Last edited by mylove4cars; 05-03-2015 at 07:12 PM.
So on a fresh oil change, the dipstick should read half a qt low?
Assume you change oil and filter. In the morning when the vehicle is cold (depending on the temperature IE. 40 degrees) the dipstick might read 1/4th to a half QTY low. Driving the car for 20 minutes and check the oil, the reading might indicate close to the upper mark on the dipstick. In other words, some check there oil level in the morning when the engine is cold and think there nearly a half QTY low and decide to top it off adding half a QTY, you might be overfilling! Check your dipstick as the manual states.
Last edited by mylove4cars; 05-04-2015 at 12:10 PM.
I looked at your post, unfortunately not to many paid attention; you would think with the many oil consumption problems and misconceptions you would have had more response.
Well the reason why is (Calibration, expansion, volume, temperature)
I think there are two reasons to check the oil level.
1. to check the operating level (of course)
2. to check for oil consumption based on how the reading changes for one to the next.
When I do a typical oil change, or add oil, I follow it with a reading done per the manual (after shutting off) to make sure it is within proper range.
But, when I already know that the level is with range, but want to monitor oil consumption very closely to see if my TL has the start of the dreaded 1 quart or more oil use per 1000 miles, I check it cold. Like the next morning cold. I believe this gives a more accurate reading.
My thinking is;
1. I know my garage temperature does not vary 20 degrees all year. My garage temp. is more consistent than what my engine temp. is after a drive depending on how hard I just drove it on the highway in the Texas summer or went easy on it to the store.
2. It gives more then enough time for all the oil to drain into the pan.
3. It allows plenty of time for air bubbles to escape.
4. The room temp. (garage temp.) oil clings to the dipstick better because it is thicker, making it easier to see the level.
I think there are two reasons to check the oil level.
1. to check the operating level (of course)
2. to check for oil consumption based on how the reading changes for one to the next.
When I do a typical oil change, or add oil, I follow it with a reading done per the manual (after shutting off) to make sure it is within proper range.
But, when I already know that the level is with range, but want to monitor oil consumption very closely to see if my TL has the start of the dreaded 1 quart or more oil use per 1000 miles, I check it cold. Like the next morning cold. I believe this gives a more accurate reading.
My thinking is;
1. I know my garage temperature does not vary 20 degrees all year. My garage temp. is more consistent than what my engine temp. is after a drive depending on how hard I just drove it on the highway in the Texas summer or went easy on it to the store.
2. It gives more then enough time for all the oil to drain into the pan.
3. It allows plenty of time for air bubbles to escape.
4. The room temp. (garage temp.) oil clings to the dipstick better because it is thicker, making it easier to see the level.
That's fine but keep in mind the above thermal expansion. If you top off the oil so that it's at the top of the hash marks when cold it will assuredly be above the hash marks while warm and possibly overfilled.
I happen to check my oil while cold just because it's more convenient to check it right before setting off in the morning. It's usually half way in the hash marks while cold which is enough room for expansion. Only if it's below that mark will I add oil.
hornedfrog's photo's also demonstrates how it is more difficult to see the oil level on the stick when hot, and very easy to see it when cold. Thanks for photos.
I believe a reading taken first thing in the morning cold, and then comparing it to another reading taken later also first thing in the morning cold, will give a more accurate indication of how much oil has been consumed opposed to comparing a hot reading to another hot reading.
Yes, I am splitting hairs here. But after hearing so many other Acura/Honda owners claiming their engines have never used ANY oil has made me wonder just how little is "ANY". Is it none whatsoever, or is it just not enough to measure from one reading to the next? That is why I have decided to scrutinize my oil level cold. It takes no more time & effort, just when to do it.
I have now given it a 6 hour "chance to settle back on to the bottom". The oil level reading is exactly the same as the post drive hot reading.
My real world experience for my car is not what the original poster has experienced. My photos show that my engine does not read 1/2 quart higher when hot. If anything, it drops, albeit, very slightly. This is despite ABDomega saying "it will assuredly be above the hash marks while warm and possibly overfilled". I don't have misconceptions, just photos.
^^^^^
Differences are best observed, engine stone cold check, engine check 2 minutes after a 20 minutes or longer drive.
Cubic Expansion of Oil 100 liters - 0.1 m3 - of oil is heated from 20oC to 40oC
The volumetric expansion can be calculated using the following equation. dV = (0.1 m3) (0.00070 1/oC) ((40 oC) - (20 oC)) = 0.0014 m3 = 1.4 liter Result: Around .06% volume per degree Centigrade in your engine.
Hot engine oil has been splashed around all over inside the engine, and hasn't got a chance to settle back on to the bottom.
After shutting down a hot engine (about 20 Minutes drive) and waiting a couple of minutes before checking the dip-stick; the amount to settle back to the bottom is about 1/16Th of a QTY.
Nevertheless, by warming up a cold engine the oil expands at .06 % per centigrade, which makes much more volume than the 1/16Th that needs more time to settle back to the bottom.
^^^^^^^ Well you’re pretty close; you’re showing an expansion around 40ml on an amount of 900ml. 4.5 QTY = 4286 ml which should add about 200ml, now add another 70 degrees Fahrenheit and your close to that Half a QTY or 0.6% per centigrade.
Using the coefficient of volume expansion of unused motor oil: .00039/F degree.
.00039/F x 70 (F deg. temp. rise) x 90 ml = 2.457 ml + 90 ml = 92.457 ml
And 92.5 ml (rounded off) is what my last photo shows. So my experiment confirms the expansion rate.
So oil does expand, and I have proved it to myself.
So why then do my hot & cold dipstick readings show almost no difference?
To have a better reading on the dipstick, try this, differences are best observed, engine stone cold check, engine check 2 minutes after a 20 minutes or longer drive. In all your posts providing measurements you did not do this. Hence, besides all the chemistry you provided hornedfrog, ABDomega and many others have performed this simple test, we all came to the same conclusion. Maybe like you so eloquently mentioned, I'm about misconceptions and you about pictures. Kidding
05-03-2015, 07:02 PM
hornedfrog, ABDomega and many others have performed this simple test, we all came to the same conclusion. Maybe like you so eloquently mentioned, I'm about misconceptions and you about pictures. 
