Tar dissolves best in non-polar solvents, which is a fancy way of saying you need an oil-based or petroleum-based product to break it down. Water and soap alone won’t touch it. The good news is that several effective options are probably already in your garage or kitchen, and the process is straightforward once you pick the right solvent for your situation.
Why Tar Is So Stubborn
Tar (whether it’s road tar, roofing tar, or bitumen) is a complex mix of hydrocarbons. The lighter fraction, called maltenes, dissolves relatively easily in petroleum-based solvents. The heavier fraction, asphaltenes, is made up of dense, high-molecular-weight compounds that cling hard to surfaces and resist lighter solvents. This is why a quick wipe with soapy water does nothing, and why even effective solvents sometimes need time to soak in before the tar lets go.
Because tar is non-polar, you need a non-polar solvent to dissolve it. Think of it like the old chemistry rule: like dissolves like. That’s why every effective tar removal method, from commercial sprays to kitchen hacks, relies on some form of oil or petroleum distillate.
Best Solvents for Tar on Metal
Mineral Spirits and Kerosene
These are the workhorses for heavy tar buildup. Both are petroleum distillates that dissolve tar efficiently, but they behave a little differently. Mineral spirits evaporate faster, which makes them better for quick spot treatments. Kerosene evaporates slowly, giving you more dwell time on thick, stubborn deposits. If you’re dealing with a lot of tar, kerosene’s slower evaporation can be an advantage since you won’t need to keep reapplying. If you buy mineral spirits, the deodorized version costs slightly more but is much more pleasant to work with.
WD-40
WD-40 works as a light-duty tar remover because its base is a petroleum distillate. Spray it directly on the tar spots, let it sit for a minute or two, then agitate with a sponge or cloth. It’s best for scattered spots rather than heavy buildup. WD-40 can strip protective wax or coatings from metal surfaces, so plan to reapply wax or a protective layer afterward if the metal has a finish you care about.
Naphtha (Lighter Fluid)
Naphtha is effective on hardened tar and tends to be gentle on painted surfaces and clear coats. It evaporates cleanly and doesn’t leave much residue. For solidified tar on wheels or chrome, naphtha is a solid choice because it dissolves the tar without visibly damaging paint or clearcoat finishes.
Household Oils
Vegetable oil, cooking spray, and even peanut butter can soften tar because their fats are non-polar. They work, but slowly, and they require more elbow grease than petroleum-based solvents. The upside is they’re non-toxic and won’t damage most surfaces. The downside is they leave an oily residue that needs its own cleanup with dish soap, and food-based products can attract insects if you’re working outdoors. Consider these a last resort when you don’t have a proper solvent on hand.
Step-by-Step Removal Process
Start by scraping off as much solid tar as you can before applying any solvent. A plastic scraper, an old credit card, or a dull butter knife works well. Avoid metal scrapers on polished or painted surfaces since they’ll leave scratches. On bare steel or cast iron, a metal scraper is fine.
Next, apply your chosen solvent. For spray products like WD-40, apply directly to the tar. For liquid solvents like mineral spirits or kerosene, soak a clean rag or microfiber cloth and lay it over the tar spot. Let the solvent sit for two to five minutes. Thick deposits may need longer. The goal is to give the solvent time to penetrate and soften the tar rather than trying to scrub it off dry.
Once the tar has softened, wipe it away with a clean section of cloth. Work from the edges inward to avoid spreading the dissolved tar across clean metal. For stubborn spots, reapply solvent and wait again. Trying to force it off with heavy scrubbing just risks scratching the surface.
After the tar is gone, wash the area with warm soapy water to remove any solvent residue. This is especially important with kerosene, which dries slowly and can leave an oily film. If you’re working on painted metal or a vehicle, follow up with a coat of wax to restore the protective layer that the solvent likely stripped.
Protecting Different Metal Finishes
Bare, unfinished metal like steel or iron is the most forgiving. You can use aggressive solvents and metal scrapers without worrying about cosmetic damage. Just dry the metal thoroughly afterward to prevent rust, and apply a light coat of oil or rust inhibitor if the piece will be exposed to moisture.
Painted or clear-coated metal (car panels, coated tools, appliances) requires more care. Mineral spirits, kerosene, and WD-40 all work, but don’t let them sit on the surface for extended periods. Prolonged contact can soften or dull clear coat. Apply the solvent to your cloth rather than pouring it directly onto the surface, and wipe promptly. Always rewax painted metal after solvent cleaning.
Chrome and polished aluminum are relatively tough, but they scratch easily. Use only soft cloths or microfiber, never abrasive pads. Naphtha is a good choice here because it dissolves tar effectively without leaving residue or attacking the polished surface. Avoid steel wool, even the fine grades, as it will leave visible scratches on chrome.
Safety While Working With Solvents
All petroleum-based solvents produce fumes that irritate your lungs and can cause dizziness with prolonged exposure. Work outdoors whenever possible. If you’re in a garage, open the doors and set up a fan for ventilation. Wear chemical-resistant gloves (nitrile or heavy-duty rubber, not thin latex) since mineral spirits and kerosene will dry out and irritate your skin with repeated contact. Safety glasses or goggles are worth wearing if you’re scrubbing overhead or dealing with splashing.
Keep solvents away from open flames, sparks, and heat sources. Mineral spirits, naphtha, and kerosene are all flammable. Rags soaked in these solvents can spontaneously combust if balled up and left in a pile. Lay used rags flat to dry outdoors, or store them in a sealed metal container with water until you can dispose of them properly.
Choosing the Right Method
- A few road tar spots on a car: WD-40 or naphtha, followed by a wash and wax.
- Heavy tar buildup on tools or equipment: Kerosene on a rag, with extended soak time for thick layers.
- Tar on chrome or polished surfaces: Naphtha with a microfiber cloth.
- Nothing else available: Vegetable oil or cooking spray, with patience and dish soap cleanup.
- Large-scale or industrial jobs: Mineral spirits in bulk. Buy the deodorized version for indoor work.
Commercial tar remover sprays sold at auto parts stores are typically mineral spirits or similar petroleum distillates in an aerosol can, sometimes blended with citrus-based solvents (terpenes) for extra cutting power and a better smell. They work well but cost significantly more per ounce than buying a can of mineral spirits. If you’re only dealing with a small area, the convenience may be worth it. For bigger jobs, a quart of mineral spirits and a pack of microfiber cloths will save you money and work just as well.