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I use a Mityvac pneumatic (i.e., air compressor) extractor. I've had it since 2016 and it works great. I've also used it to extract tranny fluid from my 2000 Ford F150 since the truck has a fill tube but no drain plug. Mityvac is pretty much the top product for extractors, though there may be some knock-offs just as good. The benefit of going with a name brand is the availability of replacement parts if you every need them (kinda like a Weber grill -- not the cheapest but can last indefinitely using replacement parts). Mityvac also has a manually pumped extractor if you don't have an air compressor.
@S-Prihadi is right to recommend a warm engine. Get the oil to operating temp (or at least 60°C/128°F) so it doesn't take half a day to suck all the oil out (that's an exaggeration). Trying to suck the oil out on a cold engine seems to take forever. On a warm engine, probably 10-15 minutes.
Thank you! I will definitely get this then. What are your thoughts on other extractors like from Holt Industries, OEMTools, EWK, LuMAX?
I see, sounds great 60C/128F it is! I was worried if 80C it will be too hot and the hose melts in the dipstick tube. I think it is the best idea to just get the one you have positive experience with, the one you linked. My broken one is not a cheap one yet it didn't last for 2 years hence why I am asking for better replacements, yours is the best solution!
I read this entire thread ...what a bunch of geeky discussion over a mere dipstick check! I love it! I dig this kind of discussion; others must simply wonder "why"?!!! LOL! Lovin the tech-education!
2015 SL400 (M276 Turbo), 2014 C350 Sport (M276 NA), 2004 SL500 (M113), 2004 Audi TT225 (BEA)
Originally Posted by W205C43PFL
Thank you! I will definitely get this then. What are your thoughts on other extractors like from Holt Industries, OEMTools, EWK, LuMAX?
I see, sounds great 60C/128F it is! I was worried if 80C it will be too hot and the hose melts in the dipstick tube. I think it is the best idea to just get the one you have positive experience with, the one you linked. My broken one is not a cheap one yet it didn't last for 2 years hence why I am asking for better replacements, yours is the best solution!
You're welcome. OEM is supposed to be a good brand, but about the same price as Mityvac anyway. Just make sure you get one with sufficient capacity, at least 2 gallons. The 7300 like I have holds 2.3 gallons or 8.8 liters. So, the 7400 mighty be a little small if that is what you are thinking.
You're welcome. OEM is supposed to be a good brand, but about the same price as Mityvac anyway. Just make sure you get one with sufficient capacity, at least 2 gallons. The 7300 like I have holds 2.3 gallons or 8.8 liters. So, the 7400 mighty be a little small if that is what you are thinking.
When engine is started , there is enough suction from the oil pump to remove oil from the disptick.
Here is when the oil dispstick tube is empty of oil.
When we stop the engine and say next day do oil level check, the first time the measuring disptick is removed, the measuring dispstick will seems empty of oil or very low level of oil.
The moment the measuring dipstick is removed, air then can be displaced by the oil which now will enter disptick tube and level itself as the excess air will vent out of the top of the disptick tube.
So wait 15 seconds or more, allow the oil to enter the dipstick tube properly to its actual oil pan oil level.....and do the oil level properly this time with the measuring disptick.
It is so simple but me forgot this basic principle.
In my country, the old days sweet soya sauce was still using oldie coca cola type of steel cap.
We need to punch 2 holes, one is for air to enter (vent) and one is for soya sauce to exit.
Our fuel tank is the same but opposite, if our fuel tank vent is clogged, we have trouble filling up our fuel tank fast...as the supposed displaced air has no exit hole.
I haven't read every line on the subject in this thread, but the above photo points me in the direction of pressure differentials owing to thermal expansion.
Borrowing this photo from a previous post. See how the dipstick tube is out in the nice (relatively) cold air? Add a decent seal to the dipstick tube, as has been discussed. You've got a set mass of air (with a temperature dependent volume) in the dipstick tube. The engine gets up to temp. Oil and air in the engine and dipstick tube all get nice and warm, only the air in the dipstick tube doesn't get nearly as hot since it has a lot of surface area per volume with air running through the engine bay over a nice thermally conductive aluminum tube to keep it (relatively) cool. Shut down the engine (necessary for this to work, as the PCV would otherwise be scavenging the positive pressure, and you'd end up with too much oil in the dipstick tube when the pressure is relieved and the hot air is allowed to escape). Things start to cool fairly quickly. The air in the dipstick tube doesn't have much volume or room to contract. Additionally, the difference between the temperature of the air in the dipstick tube is much lower than the air in the oil sump. Meanwhile, the air in the crank case starts at a higher temperature, has a much higher volume, and has a much greater temperature gradient to contract through. The air (and oil for that matter) in both contract as they cool creating a relative vacuum in favor of the block, sucking the small volume of oil out of the dipstick tube. Take the dipstick out, break the seal, the pressure differential is relieved, and you get a proper reading.
Last edited by spectre6000; Aug 30, 2025 at 11:07 AM.
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When engine is started , there is enough suction from the oil pump to remove oil from the disptick.
Here is when the oil dispstick tube is empty of oil.
....
air then can be displaced by the oil which now will enter disptick tube and level itself as the excess air will vent out of the top of the disptick tube.
So wait 15 seconds or more, allow the oil to enter the dipstick tube properly to its actual oil pan oil level.....and do the oil level properly this time with the measuring
I have a small weep hole on my dipstick tube/pipe. I don't think there is any residual vacuum (suction) in the oil pan the moment you turn OFF the engine - the dipstick tube gets vented to atmosphere.
I have a small weep hole on my dipstick tube/pipe. I don't think there is any residual vacuum (suction) in the oil pan the moment you turn OFF the engine - the dipstick tube gets vented to atmosphere.
The weep hole is a vent hole for disptick's o-ring to be able to be pulled out easier..aka break vacuum faster.
The vent hole is located a tiny bit above the o-ring.
No venting of crankcase fumes is allowed, even at oil dipstick, because we have PCV system, you should know that
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me forgot this basic principle.
