do not change the filters by miles or time, change them by fuel pressure drop only. the filter filters better the dirtier it gets, manufacturers have a end of life rating on there filters and it is not uncommon for a 2x better rating than a brand new filter. I think the shortest time I got on a 1R0749 was about 150,000, I got some bad fuel in north Dakota

 

150k on any fuel filter is crazy talk.

 

I agree with the above quote. I have a Caterpillar 10 micron filter water separator between my auxillery tank that gravity feeds the factory tank. I use a Donalson element to replace the stock Cummins element and the last filter in the chain is a 1r750 Cat element. My fuel pressure is sensed at after that. My lift pump is a Walboro 392 with the regulator set to 15psi. I can see a drop to 14psi from a full auxillery tank to a 1/4 stock tank and that is with new filters. I change the Donalson and the 1R750 when I see 12psi on the guage. Last time it had 96000 kilometers 60,000miles on them and the 1r750 is quite a lot smaller than the 1r749. I change the waterseperator element when the fuel going into the stock tank can't keep up to the fuel the engine is using
Jim O
Jim O