Never really thought about which direction it flowed , but always filled the filter with oil after a change. Clean filter and clean oil , don't see how you could introduce contamination.

 

Oil flow is through the little holes it then gets filtered and exits the filter through the big hole. If you want to prefill a filter put a plastic plug in the big hole with a small hole for air to escape and fill away allowing the oil to enter the filter as it normally would through the small holes and fill.

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Thanks, that is good to know. While the possibility of contamination is hard to imagine using new oil and filter, if one can fill an oil filter in a way to ensure that the oil entering the engine is clean (even if somehow contaminated), then why not.

 

the oil you pour in to the filter has a less chance of contamination than when you use the same bottle and a funnel to fill the motor IMO

I always prefill when the mounting position allows

 

Me 2. I personally fill it though the big hole.

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I fill it through the "big hole but when it gets to the top i let it fill through the perimeter holes also ( sure you do the same I was just spelling it out lol )

on vehicles i can't prefill i usually roll the starter but kill it before it fires up a few times

 

I fill it through the "big hole bet when it gets to the top i let it fill through the perimeter holes also ( sure you do the same I was just spelling it out lol )

on vehicles i can't prefill i usually roll the starter but kill it before it fires up a few times

I do, and that is a very good practice.

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IMO the new oil has less contamination than the old oil, and I always clean the funnel before use ,even if it looks clean, right before use.

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agree that people don't worry as much contaminating oil when they fill the motor, but in the case of the filter, the oil leaving the filter has a greater requirement to be clean as possible because it will be immediately directed to very critical and tiny spaces. Whereas contaminated oil in the crankcase mostly just sloshes around. Things like dirt and grit tend to sink to the bottom and stay there until sucked in to the oil filter.

Maybe it is just the old lab tech in me, but any way to ensure that I don't introduce something new into the oil, I like to know so that I can avoid the possibility of contamination. It is one of many reasons I change my own oil. I have no confidence that someone behind closed doors gives a hoot.

 

I pre-fill through the big hole, unless you are careless you're not introducing any contaminants.

Besides, on very cold starts the oil filter bypass opens and unfiltered oil goodness flows directly to the engine!

 

Cold oil will immediately open the bypass upon start up. So "contamination" from any source will go through the bearings anyway. Many engines have filter bypass settings that allow some amount of bypass under most operating conditions, particularly at higher RPM's. The idea is that contaminates that do manage to enter the engine oil will be picked up in the filter eventually, but not necessarily on the first pass.

Hundreds of Millions of engines have lived to old age utilizing bypass filtration. A 7.3 will too. I don't fret about it.