A Technical Understanding of the Gen5 Oil Level

[ViperSRT]

Think about it this way, it is self modulating. Let say you check it after five minutes, the oil temp (normal driving) might be 180F, therefore, it is approx 1/8 higher than if it was measured at 80F. You come back a couple of hours later and the oil temp is back to 80F, the level should lower because it is cooler, however, some top oil has leaked back into the pan - self regulating.

Wish physics were so easy. But they are not thus we have a standard way to check the level. Oil filter drainage, especially those horizontal like Gen 1 or vertical like a Pentastar V6, oil cooler drainage, especially those with thermostatic valves, main bearing clearances and sizes, oil pump leakage, lash adjuster leakdown, cam phaser leakage, etc all contribute in different ways based on the oil temperature and viscosity at the time of engine shutoff. Then you have air entrapped in the oil (called aeration) which is generally in the 5-8% region after running the engine at faster speeds, and the oil additive anti-aeration qualities, oil temperature, etc will define how long it takes for the air to come out of solution. These things also lead to considerable variations between engines of the same design. So, since the engineers cannot control the physics they control the test parameters with enough time that the fast leakage elements have returned the oil to the sump but the slow leakage elements haven't. Your study may show that your engine lacks significant slow leakage elements and/or aeration dissipation and thermal expansion counteract drainage, but that doesn't mean other Viper engines will behave similarly. Just too many variables.

In addition I believe the 5 minute period dates back long ago to when gas station attendants checked the oil after filling the gas, washing the windshields, etc. Those were the days!

[Jack B]

1/8” is a half qt on the new stick. Why ignore the owners manual recommendations?

That is basically what I said in the initial post. On my 2013 car, it is very close to the same. When they say 1/8 (.125) it could fall a little to either side, the 1/8 makes it easier to communicate. I still do not have the dipstick I ordered, however, the movement on both (new/old) versions will have the same level change per qt of oil.

Per my original thread, 10 qts equals 3" of oil in the viper pan measured at the dipstick. That would make it .3"/qt, but, the pan has a larger cross sectional area near the top of the level, therefore, the change is closer to your 1/8"/pt.

[Old School]

Some more numbers for thought. Since the inside length of the oil pan is 25" and the wheelbase is 99", there is a 4:1 ratio of height change. If the front tires are .5" higher than the rear, the dipstick will show .125" lower oil level.

[Lawineer]

Aside from fluid dropping down into the pan, thermal expansion of the fluid (which is pretty significant from 50 to 200 degrees, about 10% if I had to guess). That's like adding another quart.

[Jack B]

George

We went thru this when I did the research, Read it close. all the data is there to clear all issues. Some of the salient points are:

1. Not much oil returns to the pan after shut down, the thread give values over time. It is sort of interesting the oil level increase from the oil returning to the pan is somewhat offset by the cooling oil/volume reduction.

2 The smearing of the oil in the tube distorts the readings.

3. The first time read after the car has been shut down over night, gives the best read because the smearing is minimal,

It sounds way to simple, cover the reading area of the dipstick with a black permanent marker, it helps the read.

Jack, the photos were taken with a Canon 80D with an 18-200mm Canon lens. I had to shrink the file size to post them.

[ViperJon]

Aside from fluid dropping down into the pan, thermal expansion of the fluid (which is pretty significant from 50 to 200 degrees, about 10% if I had to guess). That's like adding another quart.

That has absolutely nothing to do with the topic being discussed. Jack B has detailed time and again with extremely careful measurements that the difference between a warm engine read and a cold engine read on a dipstick is 1/8" to 1/4" at MOST. Despite claims of it being 1/2" or more thats nonsense there is no way physically that is possible with the amount of oil in the motor and the size and depth of the oil pan.