No. It is illegal, will not work properly and R12 Freon is not available for the public to buy anyway.
No, there is retrofitting required.
An R12 system must be retrofitted to be made compatible with R-134a.
It's only Freon if it was manufactured by DuPont, but to the important things... Your 89 would have had an R12 system from the factory. You can't use R134a in an R12 system unless you do at least a partial retrofit (evacuate all the R12 and compressor oil, replace the orifice tube, replace the accumulator, replace the hose connections, add PAG oil and R134a).
It was built with R12, can be coverted to R134aIt was built with R12, can be coverted to R134a
R134a
It was built with r12. It can be retrofitted to R134a.It was built with r12. It can be retrofitted to R134a.
Was built with R12, can be retrofitted ot R134a.Was built with R12, can be retrofitted ot R134a.
The simple way is to remove the R12 and install R134A. by a kit with that will have a hose, R134A with oil. The new oil may plug your leaks. or go to Mexico and cross the border and buy R12 in 12 oz cans The border guards may take your R12 cans when you come into USA. or Drive your car into Mexico and have them fill your system with R12.
To convert a 1990 Miata's air conditioner from R12 to R134a, first, you need to recover and properly dispose of any remaining R12 refrigerant in the system. Next, replace the receiver-drier and any O-rings with R134a-compatible versions to prevent leaks. Then, evacuate the system to remove moisture and contaminants, and finally, recharge it with R134a refrigerant, typically using approximately 75% of the original R12 charge. It's advisable to have this process done by a professional to ensure proper handling and system performance.
Would have been built for R12, can be converted to R134a.
R134a.
Freon R12 refrigerant is so very expensive that I recommend you have the A/C converted to R134a. But first you must have the leak repaired. The shop will then remove any R12 left in the system, flush the system to remove the old oil, install fresh oil that is compatible with R134a, and charge the system. If there is any R12 left they may pay you to recover it.