Idle wonderings - SCR retrofit?

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Active Member
Jul 26, 2021
CLS 250
I don't drive in London except occasionally to Heathrow, at which point I'm either on expenses or I'm spending so much on a holiday that £25 is a drop in the ocean. But I'm wondering if you could retrofit SCR to an engine such as the OM651 250 CDI in my CLS estate.

It's late 2013 and apparently they had SCR from 2014 on, which I think is still the same engine, so theoretically one could add the exhaust parts, the injector and tank and convince the engine ECU to do its thing. Alternatively there's a company in Germany offering third party upgrades for 3000 € and apparently Mercedes Germany are willing to pay for it! Presumably only if you live there though.

Please - no ULEZ moaning or politics, I'm just curious as to the technical feasibility. And yes it probably is cheaper to simply replace my car with a compliant model of similar age and mileage. I'll swap for a C or E estate if anyone has a Euro 6 one? :)
I guess that apart from the technical aspects of the 'upgrade', and the notorious poor reliability of the Mercedes SCR system, and whether the cost is justified given that you only occasionally enter the ULEZ, the big issue would be persuading the powers-that-be to change the official classification of your car in order for the whole exercise to be of any value.
Value? For 3,000 € I could pay the ULEZ charge enough times to fly once a month for eight years :)
It will still be a EURO 5 car regardless of what you do to it.
I want to make sure I heard it right - you want to retrofit AdBlue to your car......? My advice is seek professional help. How long have you had these self harming thoughts? :doh:
On second thought, you can always add the system, get the car certified as ULEZ compliant, then use STAR to delete it. Technically possible, but as Dr Johnson (played by the late Robbie Coltrane) says in Blackadder Season 3: It "is like fitting wheels to a tomato: time consuming and completely unnecessary".
I also am not overly keen on spewing toxic fumes everywhere I go, but I appreciate that's not a popular idea on a car forum :) Anyway it's moot as it's not possible.
Engine swaps with individuals who have compatible engines and are willing to trade can be an option, but it's essential to consider compatibility, expertise, legal regulations, and costs carefully.
Electric vehicles which are the only alleged zero emissions vehicles are not zero emissions. They chew up tyres rapidly because of the weight. They may be classed as zero emissions but they create far more emissions in their manufacture than do ICE cars. And word is starting to spread about the likelihood of spontaneous combustion of the batteries producing highly toxic gases - if you see smoke starting to come from one, run for the hills! Their fires cannot be extinguished because when the battery goes into thermal runaway it creates its own oxygen.
John Cadogan on youtube has done several videos recently, and he is a car dealer who will sell you one if you insist, but it's quite scary. I had one for two years, never again.
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My range after two years and 8000 miles was 35 miles, in winter with rain / snow / heater / headlights / wipers. Absoloutely everything is electric remember, steering, the lot.
So I got rid of it and have recently bought a lovely reconditioned cherry red-with-lots-of-chrome W123. No computers, in fact no electrics that Faraday wouldn't understand.
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ULEZ exemption: classic car drivers find loophole to avoid paying emissions fees | Auto Express
If the ULEZ zones of UK major cities start to significantly fill up with 40 year old "classic" BANGERS expect that particular regulation loophole to be firmly closed or at least regulated out of Daily use / Commuting!:(

That's odd.

Anyone who can afford to buy a 40 years old classic / historic car, surely can afford to buy a ULEZ compliant vehicle? The start at around £1,000. And that before considering the £2,000 scrappage grant.

Either the Express is just chasing clicks, or I'm missing something here.....
£2k doesn't go very far towards a new electric car, and you wouldn't want to buy a used one needing a new £5,000 battery. I read somewhere that Volvo are making buyers of their electric car read and sign an agreement that they realise that it will not become carbon neutral until it is 7 years old. My Nissan Leaf needed a new battery (£5k) after two years and 8,000 miles because I had been a naughty boy and plugged it in when it was already 80% charged. That, Sir, invalidated the battery warranty. Did they tell me not to do that when I bought it? Guess. Anyway it's so full of computers that it shouldn't allow you to recharge it when it is already 80% charged.
I am happy to have bought a shiny beautiful restored 40 year old Mercedes to replace it, for less than the cost of the Leaf battery.

As for the Express article, there's no scandal in the Royal Family, or in Parliament, so what else have they got to talk about?
...My Nissan Leaf needed a new battery (£5k) after two years and 8,000 miles because I had been a naughty boy and plugged it in when it was already 80% charged. That, Sir, invalidated the battery warranty. Did they tell me not to do that when I bought it? Guess...

Sorry to hear that.

I think you may have a case against the dealer & the manufacturer under the Consumer Rights Act 2015 (though it's probably too late for that now?).
Found this:

"One of the most important rules of Nissan LEAF battery maintenance is keeping the battery charge between 20% and 80%. Letting your LEAF's battery die regularly or charging it to full capacity regularly will cause your battery modules to degrade faster"


But that's not official Nissan instructions... is there an official handbook that says that?

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