Thinking of getting my MR2 professionally undersealed is it worth it?

[Tomr2]

Hey everyone,

I've been looking at getting my MR2 undersealed. The car looks mostly rust-free at the moment — just a bit of surface rust on the control arms and a few other suspension parts. I'm thinking of having it professionally treated with DINITROL®, mainly as a preventative measure before it gets any worse.

I'm not planning on using the car much over winter, but I'd still like to protect it properly so I don't have to worry about corrosion creeping in over time.

Has anyone here had this done on their MR2 (or similar car)? Would love to hear your experiences — good or bad — and whether you think it's worth the cost.

A few things I'm curious about:

How well has it held up over time, especially through wet UK winters and road salt?

Any issues with peeling, trapped moisture, or needing rework later on?

How much prep did the shop do (cleaning, rust conversion, removing panels, etc.)?

If you've got before-and-after pics, even better. Thabks

[Joesson]

Not liking the idea of thick underseal coating that tend to conceal what may be occurring beneath I have tried in the past Waxoyl. This I found very temperature sensitive to apply and later that warm/ high temperatures caused it to melt and drip off onto the driveway.
No knowledge of Dinitrol.
I used Bill Hamber aerosol product on the inside the rear and front cross members of my 2 and where I did spray externally that held up well, but it never/ seldom saw rain.
As with many things you research and pay your money.
Here is something to add further thought/ confusion:


https://before-n-after.co.uk/waxoyl-or-dinitrol.html

[Carolyn]

Heavy underseal would put me off buying a car.  You never know what's underneath it.  Also I've seen cars where water has got trapped behind underseal and done real damage.

I much prefer to get the car up once a year and wire brush any rust, then treat with a good rust convertor, such as Bildt Hamber Hydrate 80, then spray over with paint that somewhat matches the colour of the car.

[Jay]

Have been using Lanoline-based spray on the fleet for a few winters now with decent results (lanoguard, Lanoshield, etc).  Really handy to apply and you can see through it. 

[Tomr2]

Thanks All this is very helpful insights I had originally planned the wire brush,rust converter and close colour match paint technique I have the Toyota aerosol spray which matches body the not the underbody so much, but not that it matters too much as most people will never see it!

[Tomr2]

Have been using Lanoline-based spray on the fleet for a few winters now with decent results (lanoguard, Lanoshield, etc).  Really handy to apply and you can see through it. 

How have you found it in hot weather I have heard it melts and things stick to it

[Joesson]

@Tomr2

Not forgetting that corrosion can typically start inside enclosed sections as I mentioned above. Particularly the rear cross member. Not so much mentioned the front cross member and I've not seen the inside of the sills mentioned, although I have heard of them rotting.

[Jay]

How have you found it in hot weather I have heard it melts and things stick to it

Haven't had that happen so far, it hardens to a wax like state.  Not saying it's never happened but would imagine you would need a specific set of circumstances for it to occur. 

Standard practice is to give it a top up every year so a quick spray every MOT seems to keep them right.

[cptspaulding]

I had the dinitrol treatment done many years ago. The car has since left these shores so I've no idea how well it's done since then.

It was done fairly local to me & the guy who did it was fastidious in hs work. I paid the extra £50 for the photos which showed various parts of the car through various stages of the work. I was happy in the knowledge it was done properly. My mechanic hated it for obvious reasons.

LIke I say I was happy in the knowledge that it had been done properly. I've since seen a number of posts on J-Spec's FB page with messy, rusty examples of it not being done properly. So either do it yourself or have confidence in the person doing it if that's the route you intend to go.

[Tomr2]

I had the dinitrol treatment done many years ago. The car has since left these shores so I've no idea how well it's done since then.

It was done fairly local to me & the guy who did it was fastidious in hs work. I paid the extra £50 for the photos which showed various parts of the car through various stages of the work. I was happy in the knowledge it was done properly. My mechanic hated it for obvious reasons.

LIke I say I was happy in the knowledge that it had been done properly. I've since seen a number of posts on J-Spec's FB page with messy, rusty examples of ot now being done properly. So either do it yourself or have confidence in the person doing it if that's the route you intend to go.

Thanks that's interesting to know, it would be intriguing to know how it has faired

[Enjay]

I got my MR2 and my MX5RF done by Preserve & Protect in Johnstone (Glasgow) about 8 years ago.  The guy was thorough and really knew both his products (Dinitrol) and was clearly a car enthusiast too.

The process took days.  He took off all of the bits (wheels, arch liners, plastic nappies etc).
The entire underside was steam cleaned.
The car was examined for any obvious problem areas and, had there been any, they would have been treated.
Appropriate areas were masked off.
Then there was the application of the Dinitrol (I forget how involved that was, but I saw them doing it on a car when I arrived to pick mine up and they were being very thorough.)
The application was guaranteed for 5 years and came with free 1 yearly inspections where any problems would be touched up for free.

I don't live near particularly near Glasgow, so I dropped the car off one weekend and picked it up the next.

8 years on and the underside still looks good and there has not been a hint of a problem for corrosion related issues with my 25 year old MR2.

So, yes, if you get a good, authorised Dinitrol dealer (vendor/applicator/wizard) to do it, it can work out very well.

Edit: I should have said, that I did get photos (and videos) sent to me during the process, so I know that they were doing everything they said they were doing.  Unfortunately, I can't find any of them at the moment.