Does extremely cold weather cause dipstick readings to be off?

[MinnesotaNole]

I always check the dipstick when the engine is cold and has sat overnight. This always results in accurate readings for me except during the coldest weather.

Extremely cold temps.; however, cause the dipstick to read low when I know there is enough oil in the crankcase.

What could cause this and how should I check my oil during the coldest periods of winter?

 

[Patman]

I found the same thing with my Firebird, if I checked the oil first thing in the morning after it sat outside in the cold winter, it would show as if it were down 1/4 of a quart. If I drove the car a good distance, then checked it 15-20min after shutdown, it would read full.

I don't seem to have this problem in the summer though, if I check it first thing in the morning it now shows the same level as it would a few minutes after a hot shutdown.

I have no logical explanation for this. I'm stumped too.

 

[cangreylegend]

"This always results in accurate readings for me except during the coldest weather."

This results in totally inaccurate readings. According to Honda manual, oil should be checked after two minutes of turning off a hot engine.

Oil does contract in the cold and you may have been overfilling. However the amount of overfilling you may have done is inconsequential or minor at worst.

 

[Dr. T]

Cangreylegend is correct. The oil contracts when cold and expands withe heat. This is even more pronounced with thicker viscosity oils. That's why when BMW switched to the 10-60 for the M3's/M5's the had special instructions to check the oil ONLY when hot (as described above...a couple minutes after shut-down). This is how I check it now too after noticing it with the M-1 15-50 and Syntec 5-50, more accurate readings are done when oil is hot.

In addition, doing a simple jaunt to the corner store and coming back...check oil...it's been known to show 1/2qt. low because it's not warmed up enough and is stuck in the engine.

 

[Al]

I doubt there is much difference-I haven't noticed any. And don't forget the crankcase shrinks in volume as it gets colder.

 

[JohnnyG]

The temperature of the oil when you check it is extremely important! The best policy is to check your owners manual and CAREFULLY read and follow the instruction for checking oil levels. I cannot stress this enough. There are many unhappy Northstar owners out there, and many other motorists (seems GM is the worst) that are unknowingly doing harm to their engines by NOT checking the oil when it's at the specified temperature. This usually results in a crankcase that is overfull, which in turn contributes to high oil consumption when the excess is scavanged off by the PCV system. Further, it is my opinion that this excessive oil burning contributes to stuck rings from the excess carbon and burned VII, starting a cycle of high oil usage. The problem is worsened by the use of oils not recommended in the manual and those with wide viscosity ranges due to the (usually) increased amounts of VII. 240 ounces of API Gravity 31.0 fluid (7.5 quarts of 10W-30 Dino) will "grow" 19 ounces when raised from a temp of 60 deg to 265 degrees. The wider the temp spread, the more it will grow.

 

[Rick in PA]

Here's a related thread.

Thinking like an engineer, I always check the oil level at it's operating condition: hot.

I suspect most folks on this board keep their oil level close to the full mark on the dipstick. Recently, I've changed my way to adding a half quart when it's a half quart low (middle of the operating range). This keeps it always in the operating range for the motor, it never has a chance to get down to the "add a quart" mark. Seems like good practice.

[ August 03, 2003, 09:21 PM: Message edited by: Rick in PA ]

 

[Chris B.]

If you check it when it is hot after you shut off the engine for a few minuts it will read low because the oil especilly synthetic is still clinging all over the engine. It is stuck in all the crevises and will not be in the oil pan for a while so your dip stick can give you a true reading. If you wait over night all the oil will be in the pan and the dip stick will tell you how much is in the pan. That is how I understand it and makes sense to me. When I check it hot it is always way low on the stick even when I put exactly 6qts in. If I wait over night it is right on the full mark. That is with EXACTLY 6 qts in the engine!!!! Check it cold when it has had time to "settle".
Can someone explain if and how I'm wrong? I'm always open to was I can protect my engines better!

 

[MinnesotaNole]

I'm with you Chris B. Check it when it's cold. Especially with synthetic.

 

[timzak]

Odd, all of my cars read exactly at the full level when checked cold after pouring exactly the crankcase capacity in. This "check when hot" thing is probably specific to a small percentage of vehicles like the Cadillac and BMW examples mentioned above.

I've found I have to wait at least 15 minutes to get an accurate reading after shutting down the engine.

Bottom line, if you're not sure, on your next oil change, pour in exactly what the manufacturer specifies (example, 5 qts in my Mustang), then check at different times to see when it reads closest to the Full mark. From then on, always check your oil at that time (be it 5 min. after shutdown, after sitting overnight, etc).

 

[DJStillman]

On my Nissan Stanza, the readings are accurate after getting to operating temperature and waiting 20 minutes, and after waiting overnight.

I tell ya', I sure love Nissans!!

 

[Spector]

All of mine read best at cold sitting in garage overnight. As the actual operating temp may vary by length of time being driven, temp outside etc. you really don't know when the oil has reached operating temp in most cases. Could be very inconsistent.

True, a garage overnight is affected by cold as well but perhaps more stable then checking when hot unless specified in manual. Cold does drop the reading slightly even in a garage. The key is to check it though.

 

[JohnnyG]

I'll say it one more time for those of you that missed it. Check your owners manual and follow the directions to the letter. The GM car I usually refer to is a Northstar Cadillac, ANY Northstar Cadillac. This one happens to be a '99 STS. They are designed to use dino oil, not synthetic, they are designed to give extremely rapid oil draindown, and they are designed to have the oil level checked when HOT. This engine holds 7.5 quarts of oil in the crankcase, but will be perfectly fine running with 5, it just won't pull 1G in a corner for very long without starving for oil. Since I usually don't drive my car that way, it is OK for me to keep my oil level at 7 quarts. This puts it RIGHT ABOVE THE ADD MARK when cold and after sitting in a garage overnight. The result? 29 MPG at 74 average MPH on a 2000 mile trip, using about 6 ounces of oil total. Specific to this type and design engine? Maybe, not many engines will even hold 7.5 quarts of oil. Can you argue with the instructions in the owners manual? I Don't Think So. Should you keep the oil level at the "FULL" mark on this engine, even when cold? NO!!!

 

[timzak]

quote:

---

Originally posted by JohnnyG:
I'll say it one more time for those of you that missed it. Check your owners manual and follow the directions to the letter. The GM car I usually refer to is a Northstar Cadillac, ANY Northstar Cadillac. This one happens to be a '99 STS. They are designed to use dino oil, not synthetic, they are designed to give extremely rapid oil draindown, and they are designed to have the oil level checked when HOT. This engine holds 7.5 quarts of oil in the crankcase, but will be perfectly fine running with 5, it just won't pull 1G in a corner for very long without starving for oil. Since I usually don't drive my car that way, it is OK for me to keep my oil level at 7 quarts. This puts it RIGHT ABOVE THE ADD MARK when cold and after sitting in a garage overnight. The result? 29 MPG at 74 average MPH on a 2000 mile trip, using about 6 ounces of oil total. Specific to this type and design engine? Maybe, not many engines will even hold 7.5 quarts of oil. Can you argue with the instructions in the owners manual? I Don't Think So. Should you keep the oil level at the "FULL" mark on this engine, even when cold? NO!!!

---

My '03 Accord owner's manual says that oil capacity is 4.4 qts. The spec. page on their website says 5.3 qts. On my first oil change, I added til I got to the full mark (cold) and ended up putting 5.25 qts in.

How did I know that 5.25 was correct and not 4.4? From the factory, the oil level always showed to the Full mark when cold. I would think the assemblers would know how much to put in.

At least in my case, the owner's manual wasn't entirely trustworthy.

 

[labman]

My physics book gives V = V0(1 + B(T1 - T2)) and B for petroleum as 0.000899/ degree C. Different oils are going to vary, it gives B = 0.000745 for ethanol. If your oil goes from 70 F to 250 F the volume will increase by V = V0(1 + 0.000899(100C)) = V0(1.0899). 4 quarts times 1.089 = 4.356 quarts. That is going to be more than enough to see on the dip stick. So read your owners manual. The dip stick was meant to be read at the temperature it says.

Don't forget the oil filter should hold oil too. After replacing the filter, even prefilled, the level should drop as soon as the engine starts. If the level doesn't stabilize soon after turning off a warm engine, I would worry about the ADBV or sludged oil returns.

 

[friendly_jacek]

In 2.5L SOHC Subaru there are marks for cold full and hot full (in addition to low cold). Almost 1 cm apart between cold and hot. The distance will obviously vary with engine designs.

 

[Chris B.]

After a run on the highway I checked my oil after 10 minutes and it was at half full. In two hours it was still hot but was almost at the full mark. Synthetic just clings to everything and that is why it shows low. You need to give it time to settle. Temperature will effect the way oil expands a little but not making 6 qts shrink down to 3 qts! The engine has 6 qts in it and in the morning it reads full! There is no way to get an accurate reading after you shut off your engine with in a few minutes. This is my experance anyway.

 

[Spector]

quote:

---

Originally posted by timzak:

Originally posted by JohnnyG:
[qb] The GM car I usually refer to is a Northstar Cadillac, ANY Northstar Cadillac. This one happens to be a '99 STS. They are designed to use dino oil, not synthetic, they are designed to give extremely rapid oil draindown, and they are designed to have the oil level checked when HOT. This engine holds 7.5 quarts of oil in the crankcase, but will be perfectly fine running with 5, it just won't pull 1G in a corner for very long without starving for oil

---

Interesting. My brother just purchased a 96 Caddy Northstar. I inspected it with him. Owners manual says 7.5 quarts with filter (no mention of hot or cold by the way) written in paint on the valve cover is 8 1/2 quarts with filter. So which is it. We asked the dealer to interpret the apparent discrepency. He said, we use 7.5 but always add a little more for this engine. So, still in the dark. Suggest going by the dipstick.

Oh, by the way, it also states in the manual that the use of synthetic 5W30 or 0W30 in very cold climates is acceptable. Sort of blows the dino only theory!

[ August 05, 2003, 03:05 PM: Message edited by: Spector ]

 

[cangreylegend]

Read the Honda manual. For Honda it is a hot engine and 2 minutes after shutoff for proper draindown.

For my legend, the TOTAL capacity is 5.7 liters but an oil change including filter is 4.5 liters cold, 4 liters without filter. That leaves 1.2 liters unchanged or nearly 20% in my engine. Your engine will be different but the key issue to remember is that depending on the engine, there might be quite a bit of unchanged oil. My oil pump for example retains its oil prime in an oil change so that's only the start plus, the fact that my V6 is 90 degrees and thus has many "catch" spots on it.

 

[Ron-Indy]

Another factor is the oil cooler. I know on my car, the cooler holds approx. 1.5 qts and has a spring loaded valve the limits flow through it at time for level checking.