Best way to improve chances of passing MOT emissions?

[Percent]

I have a 2008 Xtrail T31 2.0 diesel. Besides adding engine cleaner to the fuel [and using decent fuel [full tank?] before the test is there anything else I can do to increase my chances of passing emissions for the MOT?

[Condi]

Thrash the tits off it on the way to the MOT station. Italian tune up.

[Percent]

I'll try that. Anything else?

[Belle427]

Just keep it well serviced and use a decent fuel additive a few times a year is all I've ever done really.
Shouldn't need anything else really but giving it a bit of stick now and again will help blow the cobwebs out!

[steveo3002]

make sure servicing is up to date and when they say thrash it , it means THRASH it , not just a few revs through the gears , b0llock it along in say 3rd for a couple of miles at high revs , if its been bumbling around town all year it might need more hard driving , take it to the test center that will test while you wait , not one that parks it in a car park for 4 hrs and will test it luke warm

Edited by steveo3002 on Wednesday 8th February 11:45

[Krikkit]

Being a diesel of that age it isn't much more than a smoke test - if it won't come close then surely you've got a boost leak/overfuelling issue?

[Old Merc]

Condi said:

Thrash the tits off it on the way to the MOT station. Italian tune up.

Yes, I’ve done this for years

[Percent]

Thanks, I'll give all these tips a try, including booking a test which they'll do immediately while it's still hot.

[hairy v]

How did it do on it's last MOT?

[Lincsls1]

I recommend Cataclean.

[Chris32345]

Tank of premium fuel and some fuel additive the week before the test with hard drive before the test went ideally a few days before as well

[Steve H]

steveo3002 said:

when they say thrash it , it means THRASH it , not just a few revs through the gears , b0llock it along in say 3rd for a couple of miles at high revs ,

Edited by steveo3002 on Wednesday 8th February 11:45

Ignore this.

Aside from the risk of imminent detonation you will get more air through the system by using a higher gear and more load for longer periods. If you rev it out in 3rd you will end up throttling back most of the time and achieving nothing.

[Mikey G]

Decent fuel is a huge gain on diesels. Avoid cheap supermarket fuels as much as you can.
I had a remapped Mercedes that would only run properly on branded fuels, supermarket fuels made it smoke like fk. The difference in MOT emissions between Supermarket and branded was a huge gap between a definite pass and a close shave to fail.
I once did a road trip to Germany and had an overnight stop in Luxembourg. Filled up in a local garage not realising it was crap fuel and did a lap of the Ring on one day of the trip. Its the only time I actually 'smoked' a Lamborgini (and a Porsche etc..)

[VanDiesel99]

I'd never run any engine at consistently high revs, even though I have also been advised in the past to hold high revs in say third gear prior to an MOT. I did indeed once do so for about 30seconds before I decided this was overly harsh treatment and if this were really necessary I'd rather strip and clean the Inlet system

I will however give it the beans through the gears on 2 or 3 occasions on my way to the MOT centre, backing off in top on a Dual Carriageway then changing down to arrive at something less than approx 2500rpm, prior to accelerating hard, letting it rev to approx 4000rpm, a little short of the 4500rpm redline; before selecting the next gear (probably 4th)

In general though, the kindest thing you can do for an engine to keep it clean is give it a thrashing through the gears, every few weeks, ensure it regularly gets to temperature and give it plenty of long runs.

I was amused to find that my Missus Polo (petrol) had a significantly cleaner emissions slate at its last MOT, for being driven harder, despite the previously brand new Cat being by this time just over a year old