I see two possible concerns.

First, is the fuel lubricating the IP enough? This wouldn't be a problem with veg, but might be a problem with #2.

Second, is the veg in the tank getting hot? If so you increase the rate of oxidative polymerization. If you're looping the veg return this obviously won't be a problem. I'm currently sending the veg back to the tank, and on a hot day the tank can get very warm. I've been getting less than 2k out of my veg filters. My problem is either a) insufficient prefiltering (I filter to 1 micron but I tend to wash out the poly bag filter and reuse it, which I'm going to stop doing); b) beasties growing in the oil; or c) little bits of polymerized veg "fruit leather" from the warm tank detaching and ending up in the filter.

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1984 300D Turbo 350K 50K WVO (two tank) "Maeby"