Oil level indications while cold vs hot

[mistral cytz]

I know this has been discussed before in past threads, but I still find it surprising how great the oil level readings between a stone cold engine in the morning vs a warmed up engine can show.

I've owned numerous cars where the oil levels were almost the same readings when taken while the motor was cold or warm, but with my S4 it's a pretty large change in reading.

When cold it shows basically just above the bottom plastic knob on the stick, so about maybe 20% on the metal portion of the stick. While when at operating temperature and shut down for a minimum of 2 mins as per the Audi manual it will show 80-100% full on the stick.

It's a bit shocking when I check it cold sometimes and find that the car is showing so low since I'm still tracking my oil consumption rate. Some brands of oil darken up faster and hence show an easier reading. The Liqui Moly Top tech 4100 I'm running has stayed very clear and resulted in more difficult readings especially while warm.

Has anyone else noticed this or am I losing it?

[Kookie]

Has anyone else noticed this or am I losing it?

Huh? Mine is about a 2-3MM difference. I don't see how ambient temp could make a difference, but my area is always above 45F.. About 60F all the time in my garage.

[dparm]

The proper procedure to check the oil level is to wait 2-3 minutes after turning the car off. You have to be consistent with how you measure the level....this is common sense.

The filter housing can hold quite a lot of oil, and the valvetrain is complex enough to hold a decent amount too. It wouldn't surprise me if a 1/2 qt of oil drains back into the pan after the car has been off for a while. Regardless, it doesn't matter. Just measure the level the same way each time, and do it the way that Audi recommends.

[blaelock]

I don't think there is a particularly huge difference in the levels between hot and cold and while I'm not suggesting you try to calculate your consumption based on uncontrolled results and an inconsistent measuring method, I do think the oil level is difficult to read when hot. When the engine is hot, the oil is thinner and less viscous so it runs down the dipstick faster. When the oil is cold, it's thick and much easier for me to read.

In my experience, I can barely make out oil residue all the way to the top of my dipstick when it's warm (as per Audi procedure), but when it's cold, I can see oil coming up to a similar point point, but it's much easier to see because it's much thicker. Either way I'm getting a pretty consistent reading on my oil level and so far it hasn't gone down.

[mistral cytz]

The proper procedure to check the oil level is to wait 2-3 minutes after turning the car off. You have to be consistent with how you measure the level....this is common sense.

The filter housing can hold quite a lot of oil, and the valvetrain is complex enough to hold a decent amount too. It wouldn't surprise me if a 1/2 qt of oil drains back into the pan after the car has been off for a while. Regardless, it doesn't matter. Just measure the level the same way each time, and do it the way that Audi recommends.

Wouldn't this suggest that the oil would read higher while cold? This is the opposite for my car. Again, I'm not sure if different oils have different expansion characteristics but I'm tempted to take a picture of my oil dipstick while completely cold and once at operating temp, the difference would be a lot more significant than 2-3mm.

Here is a BMW service bulletin I just found that makes me feel a lot less crazy! It appears that oil can expand enough to make a significant difference in reading. I would say that a 10mm difference between cold and hot is very close to what I'm experiencing.

After switching off the engine, wait at least 5 minutes before checking the engine oil level. Less than 5 minutes and the oil level will not have adequate time to fully drain into the sump.

Factors that frequently make the oil level appear too low: 1) Checking the engine oil level with the engine cold and when the ambient temperature is low. At an ambient temperature/engine temperature of minus 10C (14F) the oil level is about 10mm lower than at operating temperature. This is due to the different coefficients of thermal expansion of engine oil and materials of the engine as well as the gas solubility of oil, which is influenced by other factors."
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[dparm]

That is unusual, but if the oil level reads in the "OK" zone a few minutes after shutting off, you're fine.

[httuner]

My readings aren't much different whether hot or cold and I run Mobil 1_ odd that your readings are that much of a big difference

[TexS4]

I've never checked the oil while its cold on any car unless it has not run in months or years. Then i'm only checking to make sure there is oil in it before I start.

Just like dparm stated, do what Audi suggests and do that every time with consistency and you're fine. I got really good at this while hunting down my oil leaks ;)

[mistral cytz]

My readings aren't much different whether hot or cold and I run Mobil 1_ odd that your readings are that much of a big difference

Yes I do find it odd but according to the BMW service bulletin above it can be considered normal especially with my car parked outside with temps regularly down to -10 C and colder. I'm using Liqui moly top tech 4100 5w-40 and may switch to Mobil 1 0w-40 for my next change so I'll see if that oil shows less volume change between hot and cold indication levels. As I mentioned, the change on the stick is about 10mm between cold and operating temperature.

[dparm]

Oils with higher ester content may have a tendency to "leech" and crawl up the dipstick more. Just something to think about.