Undersealing?

[krisasthecolour]

Hi guys, recently acquired a lovely low mileage late 2017 Nismo and I intend on keeping it for a long, long time. I was wondering if anyone had undersealed their 350 or 370 to protect against the salt on the winter roads? I know it's a must-do on JDM imports, but mine is a UK release and I've read differing opinions on whether undersealing is worth doing or a waste of money? 

 

Any and all opinions appreciated 👍 

[Keith D]

I don't use underseal as it can dry and crack.  I jet wash and then use Bilt Hamber Dynax.

[Stutopia]

The product you use is the tricky part - but wether or not you should protect Japanese cars from UK roads (JDM or otherwise) to me is an absolute no brainer - YES!

 

My 1998 Mk3 Hilux is like new underneath (which is good because every single panel is dented and scratched  ) because someone protected it years ago and maintained it.

[krisasthecolour]

On 26/06/2026 at 11:13, Stutopia said:

The product you use is the tricky part - but wether or not you should protect Japanese cars from UK roads (JDM or otherwise) to me is an absolute no brainer - YES!

 

My 1998 Mk3 Hilux is like new underneath (which is good because every single panel is dented and scratched  ) because someone protected it years ago and maintained it.

Thanks Stu (assuming your name is Stu haha). 

I don't suppose you've any recommendations on what style of underseal to get done ie: products etc? I gather if it's done poorly it can cause more harm than good?

[Stutopia]

I am far from expert, I took my MX5 to someone to take care of it, on the basis that before any underselling is done, it had to be prepped first. Wirebrushed off the surface rust, rust convert anything else, into the cavities etc, then it gets sealed after.

 

You're right to be cautious, I know a garage who see a lot of jap stuff and they have said since a lot of people DIY'd undersealing during the pandemic when they had lots of time and nothing to do, they've seen an uptick in rotten subframes with protection on top.

 

I am assuming that given yours is relatively new, it shouldn't be too bad underneath right now, but I would suggest you get a look under there and then either bone up on the process if you're doing it yourself, or try and find a good provider who talk you through what their process is. You can never be 100% sure, you have to trust your judgement.