If it is just bug spots(spots), then TSP and bleach in water. Trisodium-Phosphate with the bleach and laundry soap will clean almost anything safely off vinyl siding with no damage, unless you use too much TSP(it is a powder)can be bought at any Lowe’s type place or a small paint shop.
If it is guts from going splat, this cleaner will work safer, but slower, than the solvent type cleaner that Kyle mentioned.
It also kills and helps prevent mold under the lapped siding.
8 years of professional painting and repainting,