# Auto A/C R-12 vs 134a Q

**URL:** <https://boards.straightdope.com/t/auto-a-c-r-12-vs-134a-q/532682>\
**Category:** Factual Questions\
**Created:** [March 16, 2010, 7:11pm UTC](https://boards.straightdope.com/t/auto-a-c-r-12-vs-134a-q/532682 "2010-03-16T19:11:47Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![kanicbird](https://avatars.discourse-cdn.com/v4/letter/k/5f8ce5/32.png) [@kanicbird](https://boards.straightdope.com/u/kanicbird)\
**Post date:** [March 16, 2010, 7:11pm UTC](https://boards.straightdope.com/t/auto-a-c-r-12-vs-134a-q/532682/1 "2010-03-16T19:11:47Z")

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Back in the R-12 days IIRC a car took (3) 12oz cans or so to fill totally from empty, now I just noticed with 134a that it takes about 1 can, 11-16 oz is on the label under the hood. Has there been any advances in the amount of refrigerant used, or is that less is needed for 134a or something else?

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**Author:** ![Gary\_T](https://avatars.discourse-cdn.com/v4/letter/g/3ec8ea/32.png) [@Gary\_T](https://boards.straightdope.com/u/Gary_T)\
**Post date:** [March 17, 2010, 4:27am UTC](https://boards.straightdope.com/t/auto-a-c-r-12-vs-134a-q/532682/2 "2010-03-17T04:27:40Z")

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Several factors are involved. Larger cars have bigger systems than smaller cars. For a system of a given size, its R-134a capacity is about 80-90% of its R-12 capacity. There have been advances in efficiency leading to less refrigerant needed. Chances are what you’ve observed is due to a combination of these things.