4

I was taught to fill the oil filter most of the way when doing an oil change. Usually, by the time I put the oil filter back on, I'm pretty annoyed and just put the empty filter on. I do put a light coat of oil on the rubber gasket though.

Last oil change, I noticed after start up my oil pressure was very low for about 3-5 seconds. I'm sure 3-5 seconds is enough time to do a little bit of damage.

How much damage is this causing? Am I taking an hour off my engine's life or a decade?

I obviously will change my procedure next time, but I'm just curious how bad it is. My engine still runs so I know it's at least not catastrophic!

  • How low did the oil pressure go? – Zaid Aug 13 '15 at 20:40
  • @Zaid Let's call it 0 because I was more just staring at it in shock than actually reading the gauge. – Zach Mierzejewski Aug 13 '15 at 20:45
  • "Am I taking an hour off my engine's life or a decade?" - Probably much less than "an hour". When idling, the load on the engine parts is so low that you may easily cause more "damage" during normal driving, e.g. when approaching red line for a moment or something. – JimmyB Dec 1 '17 at 16:35
5

I have also prefilled my oil filters when I can. There is a notable difference in the amount of time it takes for the gauge to register when comparing prefilled to not prefilled. The difference is still fairly small though, I guess about 2-3 seconds. Although it seems like a life time while you watch the gauge. I believe this is insignificant though. If you were to check, you will see that many vehicles have filters mounted in positions that prevent prefilling. Most of them run for 150,000+ miles with out oil related issues. While I still consider it a good practice I don't lose sleep over not doing it.

2

This will create some additional wear but it's only a more severe version of what happens every time you start the engine. It's difficult to determine what effect it will have on the engine life as that might be terminated by something that's not as vulnerable to having poor lubrication for a short time, like the piston rings or valve guides.

I've never prefilled an oil filter when doing my own servicing on both bikes and cars but I'm lazy. There will still be some oil on the surfaces that are usually lubricated (despite the engine having been drained of oil) so the only surfaces that are vulnerable are those requiring pressure-fed lubrication, primarily the big end bearings. I have an old bike with an oil cooled engine with the nerve-shredding feature of producing a pronounced knocking noise (presumably a rod knock) for a few seconds when you start it after an oil change.

As an aside, I suspect you know this anyway but absolutely do not rev the engine up straight after an oil change. I like to start the engine and let it idle for at least 10 seconds to minimise the stress on it while it purges the air out of the oilways.

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