1. Uneven application overlap (“lap marks”) Sealcoat is applied in passes — either by squeegee, spray, or brush. If each pass doesn’t overlap consistently with the last, you get visible lines where one layer is thicker than the next. This is the most common cause of streaking and it’s 100% about technique, not material quality.

2. Sealer applied too thick or too thin in spots Sealcoat needs to go down at a consistent thickness across the whole surface. Low spots collect extra material and dry darker. High spots or areas rushed through dry thinner and lighter. Both show up as streaks once cured.

3. Sand or filler not mixed evenly Most commercial sealer is mixed with sand for traction and durability. If that sand settles or isn’t remixed properly during application, some sections get more grit (and a different texture and shade) than others.

4. Surface wasn’t cleaned or prepped evenly Oil residue, dirt, or old sealer left behind in patches changes how the new coat bonds and cures in that spot. Even a small oil stain that wasn’t pre-treated can telegraph through as a lighter or duller patch, even under fresh sealer.

5. Weather during application or curing Sealcoat is sensitive to temperature, humidity, and dew point. If part of the driveway sealed earlier in the day, and part sealed later as conditions shifted, you can get a visible line between the two. Wind can also cause faster drying on one section versus another, creating uneven color.

6. Sealcoat applied over an area with underlying cracks or patches If sealcoating is applied over alligator cracks or old patch repairs weren’t addressed before sealing, the sealer sits differently over those areas — thinner over raised patch material, pooling in low spots — and shows up as a visual inconsistency later.