Frequently asked questions

What is so special about New Hampshire Oil Undercoating(NHOU) ?

NHOU is a fluid (jelly like), drip-resistant, solvent-free, non-toxic, super lubricating metal conditioner infused with "active" rust inhibitors that creeps and penetrates – all in one formula! It is not a sealant that traps moisture, nor is it messy and drippy. Its active rust inhibitors last up to 12 months. Available in clear so you can actually see it preserving the original “factory new” appearance. Or choose our popular "Back-N-Black" that offers the same protection but will substantially improve the appearance of a rusty undercarriage. It will not dry out, chip or peel off and its lubricating benefits continue indefinitely. This product was developed by people who know the business (New Hampshire Chemists). It is specifically designed for automobile undercarriage protection. Oil-based rustproofing is the most effective way to treat rust and corrosion. Our oil is formulated to displace moisture and deprive the surface of oxygen. When you take either out of the equation, oxidation cannot occur, so as long as product is present rust is held at bay. NHOU is formulated to migrate and creep. This is especially important in the hard to reach areas of a vehicle (rocker panels, door panels, cab corners, cross members) that are prone to rust. These surfaces are generally unprotected (lack paint), hold moisture and are very thin.

What is NH Oil Undercoating made from?

NHOU is a combination of virgin "resolute" oils, proprietory active rust inhibitors that double as thickeners. It is a food safe grade oil, which means you can consume it in small quantities. Of course I’m not encouraging you to try! However we had a customer call last last year whose pet dog did just that. The only adverse reaction was loose stool! There are no solvents or detergents. Our rust inhibitors are green and environmentally friendly. Our NH Back-N-Black has a biodegradable tint, otherwise it's the same as the clear version.

Will it void my warranty?

Absolutely not! NHOU prevents rust and makes the vehicle work better and last longer. While the manufacturers probably won’t admit it, they just have to love NHOU because it will reduce the number of corrosion related warranty claims they are obligated to pay. It also saves customers the time and aggravation associated with claims against warranties.

Is it toxic, or does it smell?

All of our products were developed with the environment in mind. It is a product that is not subject to TSCA or is not controlled by WHMIS as it presents no health or flammability hazards. There is a slight "Cherry Chap Stick" odor for a short duration that will dissipate.

Do you clean the car first?

We perform a dry cleaning using compressed air and metal spades. Our goal is to remove dirt, heavy scale and loose failing factory coatings. If your vehicle has excessive mud due to off roading we recommend you have your undercarriage washed at a car wash 48 hours prior to your NHOU appointment.

Can it be done if the car is wet?

No. If it is going to rain the day you are to have your NHOU applied we will need to reschedule.

How soon can I wash my car?

You can wash your vehicle immediately after the treatment. Unlike other preventing methods, it will not trap moisture. It literally pushes it away, leaving behind a corrosion fighting lubricating film. We do recommend undercarriage washes as this can reduce the life expectancy of the product.

How is it applied?

NHOU is sprayed with high pressure, airless, atomizing tips which pushes the product deep into the seams, cracks and crevices where corrosion starts. Once applied, the product removes the moisture in these areas and provides a strong adherence to these surfaces, remaining active with excellent “creeping” and self-healing abilities.


You may notice smoke and odor from the underside of the vehicle the first time the vehicle is driven. This is due to a small amount of overspray vaporizing on the exhaust system. It is harmless and should cease quickly.


You may notice a grinding noise when braking. This is due to a small amount of over-spray collecting on the brake lining. This is not a safety hazard and will cease after a few stops.

How long does it last?

NHOU is recommended to be reapplied once per year if: - Its a daily driver, over 8k miles per year, driven in salty conditions or visits salt water boat ramps. - If the vehicle is secondary, and is not subjected to the conditions listed above then 1.5 - 2 years might be possible. - Do not, for any reason, wash the undercarriage of your vehicle once NHOU is applied. Make sure if you visit a car wash that they are NOT including a undercarriage rinse. This will severly reduce the life expectancy of the NHOU. Our product is more powerful than the effects of water, oxygen, salt and brine combined! You will not rust so long as our product is in place, so please don't rinse it off.

How long does it take to apply?

The New Hampshire Oil Undercoating takes about 1.5 hours to apply. You are welcome to wait for it on our comfy couch with WiFi or drop it off and return later in the day.