Supposedly, it's important to get the rust-proofing done on a warm, dry day because it's an oil product that will not dry good in temps below 50-degrees or on wet, rainy, high humidity days. It will not dry right and get washed away with the next rainy day.
Ideal rust-proofing application day is 75-degrees, sunny and dry.
www.trucktrendsnh.com ..... a new business in the old Winnisquam Auto garage in Tilton on Route-3 does rust-proofing/under coating, as well as Line-X pick-up truck liner ..... but I have no clue on their price or their ability?
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...... and, central New Hampshire is still 'cruise control country.' .....