18 February 2026 · 4 min read
R134a vs R1234yf - Why Your Car's Aircon Gas Matters
If your car is from 2017 onwards it almost certainly uses R1234yf, not the old R134a. Putting the wrong gas in damages the system and voids the warranty.
Aircon regassing used to be straightforward. Every car ran R134a, every machine took R134a, every garage on the high street could do it. Then EU law changed and the industry moved to R1234yf for new cars from around 2017. That changed the game and a lot of garages have not kept up.
Why the gas was changed
R134a is a strong greenhouse gas. R1234yf has roughly 1/1000th the global warming impact. From an environmental angle it is a massive improvement. From a workshop angle it is more flammable, costs four to five times more per kilogram, and needs a different machine that physically cannot be cross-contaminated.
Why you cannot just put R134a in a newer car
- The oils are different. Mixing them turns the lubricant into sludge that clogs the expansion valve and kills the compressor.
- The system pressures are different at the same temperature. Wrong gas runs at wrong pressure, the system never gets properly cold, and the compressor works harder.
- Manufacturers void the aircon warranty if the wrong gas is detected.
- Service ports are deliberately different sizes so the wrong machine physically does not fit. But cheap adapters exist, and they cause problems we then have to clean up.
What a proper regas actually involves
Recover any remaining gas safely and weigh it. Vacuum test the system for 30 minutes to make sure there are no leaks. If it holds vacuum, refill with the correct gas and the correct weight of refrigerant oil. If it does not hold vacuum, find the leak first. Refilling a leaking system is throwing money away because all that expensive gas goes straight back into the atmosphere within weeks.
Which one does my car take?
Easy way to check. Open the bonnet and look at the underside of the bonnet itself. There is a sticker that says either R134a or R1234yf and the exact weight to refill. If the sticker is missing or unreadable, send us the registration and we will look it up.
We have machines for both, fully serviced and calibrated. Book in, drop the car, and we'll give you a timescale for cold air and a leak-tested system.