Rinse undercarraige in winter or no?

Someone on youtube suggested that if you have already rustproofed the frame and under-body with surface shield, fluid film, etc - road salt picked up later on does not come in contact with the metal. So rinsing it with pressure, say, after a snow storm, doesn't really help, it just works to weaken your rustproofing.
What do you think?

 

Here in Colorado I’m not going to bother with fluid film etc. I use the undercarriage sprayer for my pressure washer after each mag chloride-worthy storm. YMMV, I suppose mine will too!

 

I don't overthink this type of thing. I FF or Woolwax mine before each winter and wash like normal (1 a week through a wash with brushes!). It will keep everything rust free enough that way for the 10 or so years I'll have it.

 

I fluid film in the fall and don't wash it until spring. Fluid film can be washed off with a pressure washer. My underside still looks great. Might do Cosmoline next fall though for a more permanent/longer lasting coating.

 

I have been using a house gutter spray wand attached to my garden hose to easily reach under the frame and dilute the salt off of everything. Works great and fast even in the cold weather. I've seen too many vehicles parked somewhat long term with salted undercarriages and the damage occurs quicker then you might think. It is not high pressure - so it won't blow your protectant away - kinda like driving in the rain.

 

Love the replies from folks that aren't contributing to the OP's question.

I woolwaxed mine this year but have avoided hitting those parts with a pressure washer.

 

I wash every time my truck gets salty, Im not concerned about it rinsing away the fluid film because I put the film on to protect areas that dont get rinsed very easy. There are spots on my truck that are covered in fluid film, and spots that are bare. The spots that are still covered I know dont get rinsed very well by the car wash, so the fluid film protects there.

 

I rinse my undercarriage pretty much every time i drive on salty roads.

Never had issues with rust on my pick ups.

 

Vermont here, I FF late fall and try not to wash the underside until spring. I will wash the outside, which needs to happen the next warmish day.

 

I use Woolwax which is a bit thicker than Fluid Film. It's pretty difficult to wash off but it can be done. A couple of undercarriage washes won't hurt but I'd reserve it for the heaviest of salt though.

So far my truck is 5 years old and has less (if any) rust than I see on a lot of newer GM vehicles in my area. Yay for the rust belt!

 

I use CRC Marine (cosmoline) which is very resistant to washout. I take mine through an automatic touchless car wash with underbody spray when the temps go above freezing a few times each winter.

 

I think general atmospheric moisture is important not just how much road salt there is. Do you live near the ocean? If so I think you need to rinse a lot. Desert- much less so even if there is snow.

 

In the winter, I do auto carwash with the power under-spray.

In the summer, I get the wife to do it.

 

Your wife washes the undercarriage of your truck?

 

I use NH Oil, I have had it applied twice. I was instructed not to rinse underneath which seems to have worked well, zero rust issues. The salt here is terrible, it destroys undercarriages.

 

If it isn't rust proofed rinse it often as you can, especially in New England.

 

Is she out wearing a bikini while she does it...

 

I use a watering wand with a swivel head to do a low pressure rinse.

Something like this:

https://www.lowes.com/pd/Orbit-Max-8-Pattern-Wand/1000168323

 

I have that in my Amazon cart. I think I might have enough fluid film for one more season but cosmoline is good stuff. Nasty, but good stuff.

 

I'm looking at surface shield. It says it can last up to 2 years, and the reviews seem pretty good.