Perfect C Concentration and Texture

Yes, increasing the concentration of Perfect C (Tetrahexyldecyl Ascorbate) from 3% to 5% in an oil-based formulation is likely to make the formula feel slightly thicker.

Perfect C is an oil-soluble ingredient. When you dissolve more of an ingredient in an oil base, it generally increases the viscosity or thickness of the resulting mixture. While the difference might not be extremely dramatic depending on the specific oils used in your formula, a 5% concentration will typically have a perceptibly thicker feel compared to a 3% concentration.