Both of my son’s cars (1996 Explorer and 1998 Taurus) need their AC recharge. In both cases, they slowly lost refrigerant (over 2 plus years). I’ve charged systems before but am wondering if you need to put one of those cans of R134 mixed with oil when you’re recharging, or just the R134 can by itself ?? I’m assuming that both have small leaks because the last time they were charged was a few years ago (by a mechanic).

Yes, it’s a good idea to add a bit of oil. Whenever refrigerant is lost oil is also lost with it as the oil under pressure becomes a fine mist. Sometimes you may see an oil/dirt residue that has accumulated at the spot of a leak due to this oil mist.

If I was recharging my system, I would use the refrigerant with oil in it. However, I wouldn’t recharge the system without finding and fixing the leak first.

I have recharged using a stop leak additive for a slow leak. I had to recharge every year and now it is 2-3 year intervals.

Even if it was a small or slow leak, I would still get it fixed. Recharging the system doesn’t address the contamination that is getting into the system.

It is so hard to figure out how much to put back in. Perhaps OK4550 has noticed, do you think the oil residue left by the oil used in an R12 system is easier to see that the oil residue left by a R134A system? several techs I worked with say the oil trail is not so obvious with the R134A systems. For this OP ,you should look at new driers also.

The oil mist is not that noticeable but over time the dust in the air (plenty of that in OK) settles into the oil residue and can make it pretty noticeable.

I wouldn’t bother adding oil unless you have a major leak and/or have had to top it off many times. Most of the oil is likely still in the system. I wouldn’t bother with those oil charge cans either—I’m no expert, but I think over adding oil would be almost as harmful as not having enough, and I doubt you’ve lost much. You usually need to add oil only when major service is done. It’s a sealed system and it doesn’t use oil like a car engine does.

It’s doubtful that contamination is getting into the system—the system is under pressure and is leaking out. The fact that it is under pressure makes it pretty hard for anything to get in unless you lose all pressure.

I would go with the oil. It’s probably leaked out with the R-134, but I would try to find the leak beforehand (you can buy a dye tracer kit for relatively cheap, plus it makes a fun weekend project). Also, the oil can help to deal with some of the moisture in the system. I would be willing to bet that the compressor’s life shortened because some moisture is bound to have found its way into the line; the oil will help to somewhat counteract that. Also, you may want to consider replacing the drying bulb. -Techniker

Charging an AC system - Do I need oil too?

Maintenance/Repairs

Joseph_E_Meehan June 23, 2010, 7:37pm 5

It might also be a good idea to pull a vacuum before refilling.

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Charging an AC system - Do I need oil too?

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