Two for the price of one.

My 7yo / 84K mile diesel S-Max failed its MOT at the w/end for high metered smoke. The tester has said it’s probably because it doesn’t do enough long distance high speed runs, and that’s fair, it’s not had a proper run for a couple of weeks (commute is either traffic or a 60mph limited dual carriageway). So they’ve sold me a bottle of magic liquid, told me to give it an italian tune-up and take it back.

The ‘old’ MOT is good until 8/6 but where it’s failed where would I stand on a roadside check/ANPR camera. You’re allowed to drive to and from repairers and home and the testing station to get it fixed but my ‘fix’ involves a bit of charging around in 4th gear. Does the MOT now show as fail and how quick is the ANPR system updated?

Second Q, are these injector / fuel system cleaners any cop? Worth spending out on a bottle a month, do they increase efficiency, etc?

For the cost of a bottle a month you could just buy the premium Diesel which I would have more confidence in.

fair point too….. every tank or every fourth or what?

Don’t know, never been that interested in cars.

Yes, your car still had a valid mot. But you could be driving an unroadworthy car and in theory be prosecuted for that, highly unlikely though

Yes, your car still had a valid mot.

With the new computerised systems…..no it doesn’t flags on anpr systems pretty much straight away. Twas in the news the other week a number of folk getting caught out by this.

The tester has said it’s probably because it doesn’t do enough long distance high speed runs

I’m sceptical about that suggestion tbh. It’s possible, but it could equally be another sensor giving false results resulting in too much fuel or not enough air.

nasty things aftermarket cleaners, it’s just a solvent with a weak detergent in it. As said above just use better fuel, stick to Shell/Esso/BP types and every now and then go for super duper optimax, excellium etc. They have far better technologies in them for keeping valves and injectors clean.

You’re better off looking at other issues as well, such as piston rings, are you getting through a lot of oil??

No, hardly burns any oil.

Honestly, just fill up with the premium stuff (i.e. VPower, Esso Synergy Supreme, BP Ultimate) and give it a good run as it will take a while to clean out, it will also help clean out the EGR. I’m assuming it’s got DPF as well, could have a load of shite in there not burning off properly..

Put your reg number in here to check your mot status

https://vehicleenquiry.service.gov.uk

Not sure on the detergent but my old Renault was much better after an “Italian tune”. Fuel tank down to the light, fill with posh diesel, get engine up to temperature then basically get some revs into it. Don’t even need to go fast, normal dual carriageway speeds in a lower gear do the job. A few hard accelerations do no harm either.

When my pug 205 used to fail the smoke test, 10 mins on a road/motorway in 4th at 70 had it go back to pass with flying colours. There’s a lot of soot accumulation in diesels when predominantly used at low revs and bimbling round town.

You don’t need to drive it. As long as you’re happy that you’ve kept up with all the maintenance just rev the bejesus out of it when its stationary for a while. The trouble with diesels is the particulate filters get blocked by owners doing short trips/driving like they have Miss Daisy in the back seat. You have to drive it like you stole it sometimes. Im an authorised examiner/nominated tester and used to do this to every diesel before test with no ill effects. Try it – if you get a massive cloud of soot, thats your problem 🙂