My Ford Mondeo is 13 years old. Generally the underside of the car is pretty good. The originally protected areas appear to still be in excellent condition and the protection applied when new is still sound and in very good condition.

However, what has suffered over the years are all the unprotected parts. Things like track control arms, subframes, etc. If you were really fussy about your car, which I'm not, then I would guess it would probably be a good idea to protect all these too. Mind you, a considerable amount of dismantling may be necessary in order to be able to do a perfect job.

I actually spoke to my MOT tester about this a couple of weeks ago. He confirmed the underside was in pretty good condition for a car of this age. When I mentioned about the rust which had formed on the unprotected parts he replied that they all go like that - There are no structural problems with any of them whatsoever, they just don't look very nice!

Never heard of Owatrol Oil before, but have looked it up now.

Interesting it can be mixed with oil based paints, that has interesting possibilities for chassis painting after derusting.

Wonder if its a similar product to ACF50 (similarly not cheap but quality products tend not to be), which i am now using via a spray bottle because it doesn't cover any visible rust so much as soak into it so allowing you to keep an eye on it.

The problem with car underbodies is abrasion and heavy water/salt spray, but it becomes obvious if you take an interest in what is happening underneath where the heavy abrasion and possible weak areas will be on your particular vehicle so you can give those sections a frequent blast...in my own case i initially coat the undersides and cavities) with suitable Bilt Hamber's underbody waxes, then if abrasion areas become obvious i spray with ACF50 twice a year, that method appears to be working well...the heavy abrasion and weak points on Prado/Landcruisers are both ends of the inner sills outside of the separate chassis rails, plus the chassis itself in the area and at the rear of the car, no deterioration visible since i've been using the above method, which is good because those sill areas can perforate if left.

Edited by gordonbennet on 17/10/2019 at 10:10

Owatrol is very different to ACF 50 (which is also a good product)

I sometimes use ACF50 squirted into sills and door/boot/door bottoms as it's very good at penetrating seams and thoroughly rustproofing them whilst it's at it. but on suspension parts etc it does seem to wash off after a while.

After using ACF50 I sometimes follow up with Dinitrol injection wax (on it's own Dinitrol is good but doesn't soak between seams etc)

Owatrol is very different and looks like engine oil (it isn't though) and paints on well and soaks in - it then sort of dries into a resin-esque finish and stays around even after being battered with the great British weather. It's popular with Landrover owners - it was a Landrover nut/ enthusiast that introduced me to it. Try buying a small pot to start with - it goes a long way as well.

Edited by Big John on 19/10/2019 at 22:56