Here’s Proof You Should Absolutely Pre-Fill Your Engine’s Oil Filter

There are countless theories online explaining why you should or shouldn’t pre-fill your oil filter when changing the oil in your engine. But theory only gets you so far. Here’s real, scientific proof you should always pre-lube your engine’s oil filter before you install it. 

Lake Speed Jr. from The Motor Oil Geek YouTube channel got some flack for pre-filling his engine’s oil filter during an oil change video he published to his channel. To prove the haters wrong, he teamed up with dyno expert Don MacKaskill to perform an experiment using a V-8 sitting on an engine stand.

Most engine oil pumps get oil directly from the filter, so to prove why pre-filling is so important, Speed Jr. set up an oil pressure gauge to show what would happen if the engine ran with a dry filter. Priming the engine (spinning it without adding fuel or spark) reveals that the engine would run for a couple of seconds with no oil pressure at all, as there’s no oil to take from the filter. 

Speed Jr. then primes the engine again after the oil’s been circulated through to the filter. In contrast, pressure builds immediately, erasing any possibility the engine could’ve run without a supply of oil. 

Whenever you do an oil change your engine will have some residual oil coating the internals, so it’s not like you’d be running the motor totally dry if you didn’t pre-lube the filter. But as Speed Jr. points out, that thin layer of residual film isn’t enough to keep things like rod bearings properly lubricated, even for a few seconds. Deciding not to pre-fill your filter means more wear for your engine, full-stop.

Some cars have filters that are mounted sideways or upside-down, making them tougher to pre-fill without making a huge mess. Some modern cars have a feature that solves for this problem, as Speed Jr. points out in another video. You can use “clear flood mode” to spin the starter without starting the engine, allowing the oil to circulate to the filter. Activating this mode usually involves a pedal dance that can differ between manufacturers; we suggest consulting your owner’s manual for instructions on how to use it.