A little zinc in the lube oil is usually good (zinc is an anti-wear additive), but zinc in your fuel is not good (leads to galvanic corrosion and varnish deposits).
Regarding injector wear, since last June-July all US refineries have been producing Ultra Low Sulfur Diesel (15 ppm or less Sulfur). When one extracts some of the longer hydrocarbons and almost all of the sulfur from diesel fuel, most of the lubricity of the fuel is gone. To overcome this a lubricity additive is injected into diesel fuel as the ULSD is being pumped into fuel tankers. The alternative to a lubricity additive is the addition of about 2% soy-based biodiesel. The test standard is a max scar of 520-microns in what is called the HFRR test (High Frequency Reciprocating Rig)...most fuel terminals add enough additive to get a 460-500-micron max scar...addition of 2% biodiesel will give a 320-micron scar.
The real kicker here is that most heating oil is now Ultra Low Sulfur Heating Oil (comes thru the same pipeline and is stored in the same fuel tanks at many fuel terminals)...red dye is added, but NO LUBRICITY ADDITIVE is put into the heating oil. When one buys heating oil and burns it in ANY diesel, unseen damage is being done to the injection pump and nozzle(s). If you are burning 15 ppm sulfur heating oil, be certain to put lubricity additive into the heating oil. To avoid road taxes when buying diesel fuel, buy Off-Highway Diesel Fuel. Any fuel sold as diesel fuel will have the lubricity additive (or 2% biodiesel) in it and will run fairly well in any diesel.
Of interest is Caterpillar's stance on biodiesel fuels...any heritage Cat engine (C-series, 3208, 3306, 3406, 3408, 3508, 3600-Series, etc.) is good up to B30 (30% soy-based biodiesel). If using above B30 (B40, B60, etc.), any fuel related problems are yours. On heritage Perkins engines (Perkipillars) the biodiesel limit is 5% (B5). Apparently there are problems with higher percentage biodiesel in engines with rotary fuel injection pumps (Ford, GM, Perkins, Mitsubishi, etc.), although I do not know the precise nature of the problems.
Swedgemon
Somewhere in Kentucky
GM-90 6/1