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Why Is My 453 Listed As A 451?

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PremiumNo Difficulty Mod ID1801 Creditevilution For453 EQ453 Fortwo/Forfour Link Copy to Clipboard

Your 453 Is Listed As A 451 In The Documents

453s in most EU countries had 451 on the ownership documentation. WTF!

Photo by Giampiero M
Smart did this because Mercedes were dodgy wankers trying to get around stupid “green” rules.

The EU had mandated that all new models built after 2012 had to comply with certain air conditioning regulations. Smart claimed that the 453 was just a facelift 451 to get around these regulations because it was an existing model.

They managed to get away with that for many years but eventually started using the less effective (and more flammable) R1234YF air conditioning gas when the laws changed. Mercedes, amongst a few other German manufacturers were dead set against using this new gas (because it was shit) so they dragged it through the EU courts for as long as they could so they didn’t have to comply.

Eventually the EU successfully changed the law* so that all cars built after January 2017 had to use refrigerant gases with GWP lower than 150. The traditionally used refrigerant in car AC systems was R134a and that had a GWP of 1300 (later amended to 1430) so it was no longer suitable.

New Law

*(MACs) (Directive 2006/40/EC).


Global Warming Potential.

GWP Values

It’s worth noting that the higher the GWP, the more effective that suitable gas is for cooling in AC systems.

Carbon Dioxide – 1 (baseline for GWP values)

R12 – 8500 (never used in smarts)
R22 – 1810 (never used in smarts)
R32 – 675 (never used in smarts)
R134a – 1430 (used in all smarts up to January 2017)
R1234ze – 7 (never used in smarts)
R1234yf – “less than 1” (used in all smarts after January 2017)


It’s flammable, doesn’t cool as efficiently, costs a lot more to produce, costs way more to buy, required special hoses and ran at a 40% higher pressure than the previous r134a.