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Why does the dipstick read higher the second time?

Ever notice if you look at the level on the dipstick it reads low before you wipe it off and get a second reading? At first you could say the second reading was erroneously high due to oil sticking on the dipstick tube. But that can’t be for two reasons. Sometimes the first reading is dry and therefore can not be leaving oil on the tube. Secondly if it was on the tube it would be patchy on the whole length of the dipstick, not just at one location exactly between the marks. Doesn’t make sense…it seems like it would be the other way around. Same holds true for all 3 of my cars and my boat. Any ideas? Why is that first reading dry, or very low? Some kind of weird voodoo I suspect.

I haven’t noticed this. Some cars have a very curved tube for the dipstick and it is possible for oil in the tube to get on the dipstick. Also I make sure not to check the oil for several minutes after shutting off the motor.

In an operating engine, it takes at least an half hour before 90% of the oil drains back down into the oil pan where it can be measured after the engine is shut off…The BEST time to check the oil level is first thing in the morning, before the engine has been started…

I always look at mine after it’s been sitting for a long time. I never have that issue.

I too always check my oil first thing in the morning when the oil has had all night to run back down into the oil pan. Just seems like the logical time to check it. When on trips I try to check the oil at gas stops after pumping the gas and often get various readings because the oil is still running back into the oil pan. For those times as long as it’s within the safe zone I close the hood and check it again the next day when I’ve arrived at my destination and the oil has had time to drain down.

I like to check oil before the engine runs because everything is cold and I only have to remove the dipstick once. The oil doesn’t run off the stick as fast either.

We have had recently, a post concerning too much oil in the crank case after a dealer service oil change. This discussion is a big reason why that happens. Oil changes and not waiting for all the oil to drain down while filling leads some of us to do a little CYA and add that extra half quart.

It’s a lot easier to measure out 6 then 5.5 quarts or wait 10 minutes or a more accurate reading. Overfill for me is typical in the fall when changing oil in a gazillion vehicles and tools time to play golf is limited. Back yard mechanics as well as the most experienced have often been guilty of not waiting.

Overfilling can cause problems.   It can cause foaming of the oil and prevent proper lubrication.  Stick with the correct fill.   Too much is not good for your car.

I have never once found a dipstick dry on the first check if there was sufficient oil in the crankcase. I have the exact opposite experience. It always shows a bit higher due to the agitation from prior running. The second read after wiping it off is the correct level. Subsequent reads often have some oil on the stick edge from oil dragged up the tube but it is obvious where the fill level line is located on the stick. The only scenario I can envision is if the return galleries in the engine are plugged up and it’s taking a long time for the oil to make its way back to the crankcase.

First thing in the morning is best for checking, but when doing it at gas stops on road trips, pump your gas, wash the windows, pay for the gas and THEN check the oil. Give it a chance to run back into the pan from the engine.

I too have never faced the phenominon you describe. Like others, I always check first thing in the morning when it’s all drained to the pan, except when I change my oil, wherein I run the engine for a few minutes and then let it run down and check it. Truth is, the engine is quite capable of dealing with an extra 1/2 qt or so without any problem. The level need not be perfect, only between the ADD and FILL lines.

In my years as a pump jockey I’d check the oil on a hot engine, and given the couple of minutes it took, I didn’t see the oil rise much, if any, from draining. I’ll check my oil a couple of times when I’m getting gas, and I also don’t see an increase after the car has been sitting for a short time. My conclusion? The oil drains back pretty quickly in a hot engine.

Taking the dipstick out to wipe it off doesn’t count as a reading, otherwise you wouldn’t wipe it off. So are you taking the dipstick out three times?

Quote Texases: " The oil drains back pretty quickly in a hot engine."

In my experience, you are absolutely right. Maybe two minutes tops. I’ve checked LOTS of them after a couple of minutes, and then much later, finding no difference on the dipstick.

It dosen’t if you wait a few minutes to first check it.