fuel restriction gauge

On a fuel pressure restriction gauge that reads 0 to 30... When should you change your fuel filter at which reading maybe 15 or 20?

 

What's this on ? Engine, vehicle ?

 

I guess on a C15 acert Caterpillar

 

On a 2006 C15 acert Caterpillar

 

My preference is anything over 10 lbs vacume. Normal should be around 5 to 8. I run a win 33339 filter on my primary filter base. And only pull 3 to 4 lbs.

 

I guess the only reason I'm asking is because are used about three different brands this month and they're only lasting about a week maybe 10 days.. It must just be the winner fuel or something

 

Or you have alge growing in your tank. Are the plugging up ? Do you see blackish grey slime when you pour the filter. If so it's alge.