I didn’t mean to sound abrupt Dave and if I did I apologise, I wasn’t speaking about any one person in general, plant machinery is robust enough to stand up to jet washing regularly unlike a lot of car’s especially older soft top models. Like I said it’s entirely up to the individual how they treat their cars. I prefer to treat my vehicles with a little more reverence. I have spent many years in the car refinishing trade and heavy transport and I to speak from experience and the condition of my 20 year old vehicle stands testament to that.
I too looked at all these devices but was unconvinced about using a pressure washer in areas which I could not see. So I made my own, using a length of scrap timber and an old garden lawn sprinkler. Attach a hose and move it under the car, it works great judging by the residue it leaves on the tarmac after using it. Cost zero!
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…brilliant idea!!..
I have had a Karcher variojet nozzle for several years and do both my MX5 and my Lexus RX450 with it. Brilliant piece of kit and cheap, and a standard Karcher (other brands are available also 
) deliver plenty of power. Just keep hold of the lance with 2 hands!!!
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I cannot understand using a pressure washer on chassis members which have drain holes directly in line of fire ? Surely there is a risk of filling some of these areas with unwanted water?
It is the high pressure that worries me.
cheers
I’d rather displace encrusted salt with fresh water which in the long term should be much less harmful.
Pressure control is important when using washers on cars, the karcher attachment and the K4 washer I use have pressure control settings.
Modern vehicle design and consideration of the de-icing activity in designing and building road structures have both helped to reduce the impact of corrosion. Vehicles and metal structures exposed to salt should be cleaned down regularly to avoid accumulation of salt. The general objective should be: As much as necessary, as little as possible.
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hi, I can understand regular cleaning the underside but using a pressure washer like has been suggested the operator cannot see what they are doing. By all means use a washer but try and see where you are pointing it. Up on a ramp makes it easier but down on it’s road wheels is much more difficult. Just an observation really - I am washed out now.
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Methinks some are overthinking this subject… 
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Nice one… just ordered one… reviews generally good on Amazon.pricey for a small bit of plastic but if it does the job …fine
I use my garden hose with a Hozelok multi spray head wedged between the tines of an upturned garden rake.
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I’ve got this Nilfisk underchassis nozzle and I really rate it despite it seeming a bit expensive at £20. It gives quite a wide fan so covers a good area and isn’t too intense; downside if you have to crouch down with it as it’s on the end of the regular lance and then waggle it about underneath the car so might not be great for older members! It also gets run around the arches pointing up and down. I only usually bother with it in winter to get the salt off. A garage once joked they’d refuse me an MOT as it looked too clean underneath!
The trick with any pressure washer is to spray at a 45 degree or shallower angle so you’re not blasting the dirt in deeper! And not directing at weak points like brake calipers and tyre beads.
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