When is the best time to check the oil level?
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Patman I have noticed the same thing in my vehicles. I always check the oil after running the vehicle warm and then letting it sit for 20 minutes prior to checking.
Patman
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I guess from now on I better continue checking only after a short cooldown after running it a while, that way I don't overfill.
Patman, like you I've always checked my oil when cold because I thought it allowed time for the oil to drain down to give a more accurate reading. Just for giggles I looked at the owner's manual for my '96 Contour and low and behold they say the oil must be warm to check it! My 2002 F150 owner's manual doesn't say specifically but since they say..."Turn off the engine and wait a few minutes for the oil to drain into the oil pan" I'm assuming it's to be checked warm. I learn something everytime I check in on this site!
You just keep proving that old adages are just that, OLD! My wife says I'm addicted to this site. I that possible?
Whimsey
Whimsey
Sorry, the last sentence should read "Is that possible" ...Too much oil on the brain...must resist...Noooo!
Whimsey
Whimsey
Patman
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With my Firebird I have always checked the oil first thing in the morning, but when I checked it today and saw it was down, after just checking it last week (less than 400 miles ago) I couldn't believe it was down again.
So I drove it for about 20 miles and then went into Walmart for about 10min, and came back out and checked it again. It showed full this time.
I figured it would show more full when cold!
Perhaps I've been overfilling this car all along, and might be burning more oil than I should as a result.
From now on I will only add 5.25 qts at oil change time instead of 5.5, and I will check the oil when hot and not let the level get as high as before, and see if the consumption is any less. It was only using one quart per 6k before (mostly leakage from the intake), but it appeared this morning as if that consumption had quadrupled if it was truly down from last week. Maybe with this extreme cold weather it's not giving proper readings when I check it after it's been sitting overnight perhaps?
So I drove it for about 20 miles and then went into Walmart for about 10min, and came back out and checked it again. It showed full this time.
I figured it would show more full when cold!
Perhaps I've been overfilling this car all along, and might be burning more oil than I should as a result.
From now on I will only add 5.25 qts at oil change time instead of 5.5, and I will check the oil when hot and not let the level get as high as before, and see if the consumption is any less. It was only using one quart per 6k before (mostly leakage from the intake), but it appeared this morning as if that consumption had quadrupled if it was truly down from last week. Maybe with this extreme cold weather it's not giving proper readings when I check it after it's been sitting overnight perhaps?
The reps at Cummins and Detroit Diesel have told me to wait fifteen minutes after hot shutdown to check oil level on Class 8 rigs. Not less. Always figured that was good advice on a little gasser as well while on road trips.
Hadn't heard of the OEM "hot" recommendation before, (nor the above-recounted experiences). I always went by the park-on-level-ground-check-in-morning routine.
Always learn something new at this site!
Hadn't heard of the OEM "hot" recommendation before, (nor the above-recounted experiences). I always went by the park-on-level-ground-check-in-morning routine.
Always learn something new at this site!
Patman
Staff member
The funny thing is when I had my LS1 Firebird it's manual said to only check the oil a few minutes after a hot shutdown. I tried that with my car, then checked the level again 12hrs later and it showed the same.
So perhaps it's only in the extreme cold weather that I will see a difference in levels from hot to cold on my current LT1 Firebird?
So perhaps it's only in the extreme cold weather that I will see a difference in levels from hot to cold on my current LT1 Firebird?
Well, oil does, I believe, expand some when hot, thus you may get a higher reading when the oil is warm. I check mine in the AM when cold and sitting overnight. Sometimes i do get the same reaction where it seems too low at this time, however, it seems that the cold reading is usually the correct one for me.
Consistency is the key if you are looking for oil consumption. If all you care about is whether it is between the hash marks, about anytime or method will work.
Consistency is the key if you are looking for oil consumption. If all you care about is whether it is between the hash marks, about anytime or method will work.
There's an interesting related thread: http://theoildrop.server101.com/ubb/ultimatebb.php?ubb=get_topic;f=1;t=001298
I'm going to try thinking like the engine designer here.
On one hand, it would be best to calibrate the dipstick for typical operating conditions. There would be no need to introduce "offset" into the measuring device. The oil level could be checked periodically during highway travel. The oil level would measure accurately after an oil change. Etc.
On the other hand, it would be poor design to have a device that absolutely needed it's lubricant level set just-so. If the engine would destroy itself if it was run a little low or a little high, there are going to be a lot of dissatisfied customers. Therefore, like all designed things, there's an overfill/underfill safety factor. How big is that safety factor? I don't know, but if it were me, I'd allow the user to be "stupid once" but not "stupid twice" in regards to overfilling.
So, I suspect the oil system will tolerate being checked for fill level hot or cold. And I suspect that it's best checked hot. And if I check it cold, I'll mentally add a little for expansion. But I darn well better check it.
I'm going to try thinking like the engine designer here.
On one hand, it would be best to calibrate the dipstick for typical operating conditions. There would be no need to introduce "offset" into the measuring device. The oil level could be checked periodically during highway travel. The oil level would measure accurately after an oil change. Etc.
On the other hand, it would be poor design to have a device that absolutely needed it's lubricant level set just-so. If the engine would destroy itself if it was run a little low or a little high, there are going to be a lot of dissatisfied customers. Therefore, like all designed things, there's an overfill/underfill safety factor. How big is that safety factor? I don't know, but if it were me, I'd allow the user to be "stupid once" but not "stupid twice" in regards to overfilling.
So, I suspect the oil system will tolerate being checked for fill level hot or cold. And I suspect that it's best checked hot. And if I check it cold, I'll mentally add a little for expansion. But I darn well better check it.
Let's see...
You have the thermal volumetric expansion of the oil when it's hot, it could be higher. Then you have the thermal expansion of the dipstick, going deeper into the fluid. So it probably does make a difference.
I check my owner's manual to see what they recommend. Typically it's when the car is warm, since you'll typically be checking it at a gas station or out on the road.
After I know what the owner's manual says, I compare the hot reading to the cold reading the next morning. Then I have a good reference and can check it anytime I want and know what effect temperature has on it. Typically little or nothing, surprisingly. On my S2000 I prefer to check it cold because my dipstick is narrow like wire and hard to read. On my other cars, they have big flat dipsticks, so I check it hot.
Don't forget, in the real cold weather your oil can actually "expand" because of condensating moisture.
You have the thermal volumetric expansion of the oil when it's hot, it could be higher. Then you have the thermal expansion of the dipstick, going deeper into the fluid. So it probably does make a difference.
I check my owner's manual to see what they recommend. Typically it's when the car is warm, since you'll typically be checking it at a gas station or out on the road.
After I know what the owner's manual says, I compare the hot reading to the cold reading the next morning. Then I have a good reference and can check it anytime I want and know what effect temperature has on it. Typically little or nothing, surprisingly. On my S2000 I prefer to check it cold because my dipstick is narrow like wire and hard to read. On my other cars, they have big flat dipsticks, so I check it hot.
Don't forget, in the real cold weather your oil can actually "expand" because of condensating moisture.
All liquids contract as they approach their freezing point. Water, however, is unique in that just before it solidifies, it expands to a volume of ~7/8 the density of liquid water. It has to do with with the polar nature of water and how its molecules align when it crystalizes. That's why ice floats in liquid water. (1,200 people or so got an object lesson on the aberrant cold fluid/solid state dynamics of water aboard the Titanic...) Since motor oil continues to contract until it freezes, it stands to reason that in extremely cold climates, the oil level will be uncharacteristically low on the dip stick if it's measured with the oil at ambient temperature. It also stands to reason that the engine oil level will be at its most accurate if measured at operating temperature with sufficiient time to drain back into the sump. I don't doubt that Cummins and Detroit Diesel reps have their reasons for their recommendations, but for little gassers, 15 minutes might be unnecessarily long - especially if you're on the road at a gas station in sub-zero temperatures and want to get going again. (Brrrrr!) Once the oil level is correct for the operating tempperature, then when the oil has cooled to sub-zero ambient temprature range, just scribe a mark at that level on the dipstick. Then whenever the level is checked at any temprature down to as low as the lowest anticipated temperature you'll encounter, you'll know whether it's at a safe level if it falls between the hot full mark and your cold scribed mark.
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