Best Undercoatings of 2025

“I sprayed nearly the entire underside of my truck, and it's holding up really well after about two months. I even coated my fenders to prevent rusting. It definitely sticks, as I've pressure washed the underside three times, and it hasn't budged. Just a heads up, it’s tough to remove from boots, so I recommend wearing a mask during application.”

“As an auto dealer, I frequently choose this product for undercoating. It’s a fantastic deal and perfect for protecting trucks.”

“I’ve used this product multiple times, and it’s a solid undercoating option. It covers well and is easy to work with. The great pricing encouraged me to buy five cans!”

"I've used many undercoatings while restoring classic cars, and this product offers the best bang for your buck. It has good adhesion, and while I believe 3M's undercoating is the best, this one is considerably less expensive. My classics have impeccable undercoating, protecting them from rust and grime."

"I applied this undercoating on my 2015 Jeep Wrangler JK after treating the rusty spots with a rust converter. It gave a rubberized black appearance that adds extra protection. I recommend using at least two cans for full coverage, and it works well even on surfaces that aren't fully visible."

"I appreciate Rust-Oleum's great products, and this undercoating spray is no exception. It sprays evenly from various distances, making it easy to achieve good results. Just remember to shake the can well before use!"

"I've used this product to undercoat my 2014 Ram 1500. I applied it to the cab mounts, frame rails, and wheel wells. As of January 15, 2022, I don't see any signs of rust. I ordered it again for a new truck arriving in March and plan to apply it similarly. My previous experience shows it dries nicely and isn't sticky after a day. It even offers some sound deadening. Compared to other brands, 3M is the best for even spraying. I'm confident it will perform well."

"This product is great for coating my truck's chassis and frame. It took about 12 cans for my short bed pickup. After cleaning the chassis of oil and rust, I applied two layers, and I'm impressed with its strength after 24 hours. I trust 3M products, but I always prioritize safety. Be sure to wear a mask, glasses, and gloves as the odor is strong."

"I find this product to be excellent, but it doesn't go very far. I recommend ordering extra cans to avoid running out. Expect some overspray and occasional dripping."

"I strongly recommend this product. It's strong, easy to apply, doesn't chip, and bonds extremely tightly. I bought an extra gallon to ensure it was as thick as I wanted for my old Chevy frame, and it hasn't let me down yet. I saved a ton of money by doing it myself, and I think it turned out even better because I took the time to cover every crack and crevice."

"Overall, this worked mostly as expected. I was pleased with the results and would use it again, but there are a few things to keep in mind. The coverage isn't great. The instructions suggest 2-3 coats, which might work for small projects. I ended up purchasing a second kit for a second coat. Unfortunately, there's no economical way to buy more without getting another gun. While the gun is mostly well-made, the plastic trigger often slips off the plunger, and the pressure gauge is pretty much useless—just an on/off switch."

"I used this to undercoat a vintage car. The product is made from asphalt and resembles what was used in the 1930s. It applies smoothly and with low overspray. However, the solvent caused peeling on certain paints, so I recommend testing a small area first. The odor is strong, so using it outdoors is best. The coverage was lower than expected, so I suggest buying extra. The provider sprayer worked well for me."

“I highly recommend this product and the Woolwax spray gun kit! I coated my truck and van with 1-1/2 gallons. It looks great and holds up well. I plan to do it every year.”

“This stuff is perfect for slowing down rust. I use it on all my vehicles. This time, I only bought one gallon for touch-ups. I apply it heavily, and it takes about 2 gallons for a full-sized truck. I’ll buy it again!”

“This is a must-buy! The big jug is a great deal. I’m using it to coat my running boards on my Chevy Trail-Boss. My friend’s running boards look brand new after months. It protects and looks professionally done.”

"I used this product on my 2024 F150 rear fender wells and it worked great! I managed to cover both wells with just one can. I applied a light coat for paint protection before adding plastic fender liners. If you're planning to use it solely for fender well protection, I recommend one can per well. The spray nozzle is just perfect for the job!"

"I applied this product to the inner fender wells of my pickup, trusting the good reputation of 3M. I was pleased with how nicely and evenly it applied, and it dried quickly, allowing me to add a second coat in about 10-15 minutes. It doesn’t drip, which is a big plus for me! The finish is a smooth, slate gray, and I’m optimistic about its performance, although I haven't yet tested its durability in tough conditions. I have half the can left, which is a good value for the price."

"After spraying this on the trailer frame and substructure, I found it to be very tenacious. I'm curious to see how long it will last. Overall, I feel confident in my purchase."

"I applied this product with minimal mess and no smell. The black finish made my chassis look new again while preventing rust. I recommend getting a hand pump for easier filling—it goes a long way on multiple vehicles!"

"I protect the frames of my rental golf carts with this product. It works great and makes the undersides look brand new. Just a heads up: it doesn't dry, so I have to be cautious while working underneath. I'm always happy with the results!"

"Living in the Midwest, I drive old vehicles, and this product helps combat road salt and rust effectively. It sprays nicely from the WoolWax gun and covers very well. The smell isn't too strong, and after a few months, it pretty much vanished. I had enough product from the 5-gallon bucket to do complete coverage on three full-size pickups!"

"I've been using this undercoating for two decades. It can be quite messy and never comes out of clothes, but it’s incredibly effective. I coat surfaces whenever I replace parts, and it has virtually eliminated rust jacking for me. I did extensive prep work and applied it thoroughly, and after five New England winters, I see zero visible rust."

"We used this product to refinish our livestock trailer. After proper preparation, we applied it undiluted with the recommended equipment and were pleased with the results. We used almost 2 gallons for the frame and supports, and the product was already drying on a 70-degree day. It’s a sticky mess, but cleanup was manageable with some gas or paint thinner. Overall, we are satisfied and will definitely buy it again."

"I discovered this undercoating through a YouTube video. It’s extremely thick and adheres well to surfaces. For the best results, I applied layers with two hours between coats and waited up to 24 hours for curing. This product gives off strong fumes, so be cautious in closed spaces. It looks nice with a high-gloss finish and seems resistant to dents, although it can scratch. I would rate it higher if the drying time was shorter."

"I won't purchase this again. The spray started off well but then began sputtering. Even with a heated garage, all six cans I tried sputtered within a minute."

"I’m going to stick with my original undercoating brand, as this one just didn’t meet my expectations."

"I found it easy to apply. The tip popped off occasionally, but it was simple to put back on. I also have a spray gun, but I found this just as effective. It worked well on my car, although my coverage wasn’t as wide as with the air compressor."

"Initially, I was skeptical about the aerosol version compared to the pail. However, Woolwax has proven to be a high-quality product. It penetrates crevices better than thicker non-aerosol options. I did receive a damaged sprayer, but Kellsport resolved it quickly without hassle."

"I've switched from Fluid Film to Wool Wax, and it’s a superior product. It applies thicker and is less likely to wash off. I used it on multiple vehicles and found it very effective. The smell is noticeable, but it fades over time. Living in the Rust Belt, this is an essential item for maintenance."