Rick's Free Auto Repair Advice

Add AC oil

How much AC oil to add?

When replacing AC parts, how much oil should you add?

Start with the right AC oil

Car and truck AC systems rely on circulating oil to lubricate the compressor. But just like engine oil, not all manufacturers recommend the same viscosity AC oil for their systems. For example, for R-134a refrigerants there are many different viscosities: PAG 46, PAG 100, PAG 150. A Sanden SD7H15 compressor requires SP-15 PAG oil. Sanden SD5H requires SP-20. Sanden compressors used in GM, Honda, and VW models specify SP-10.

Auto AC compressor oil PAG 46 oil

PAG-46 AC compressor oil

AC compressor oil PAG 46

PAG-46 AC compressor oil in pressurized can

AC compressor oil PAG 46

AC compressor oil with fluorescent dye

If you add too much AC oil

Every time you lose refrigerant, you also lose some AC oil. So it’s common for DIYers go overboard and add more oil every time they add refrigerant. But that’s can be self defeating if you add oil every time you recharge. Too much oil decreases cooling because it coats the interior fins and blocks heat transfer.

When a shop evacuates an AC system, they measure how much oil came out and replace it with the same amount.  But how are you supposed to know? Well, if your system is down a few ounces of refrigerant, you can safely add more refrigerant without adding any oil.

You lose AC oil when you flush an AC system

Many AC component manufacturers also recommend flushing the

flush AC system with AC flush kit

Flush with an AC compatible fluid and flush it.

entire system when you replace a major component, especially if the compressor has failed. Here’s a chart that shows how much AC oil to add after flushing when you replace these components:

Component     Amount Of Lubricant To Add

Accumulator               2 oz.

Condenser                   1 oz.

Evaporator                  2 oz.

Filter Drier                 1 oz

How much AC oil to add to a new compressor?

Some compressor come with oil already installed and others come empty. If the compressor is empty, you MUST measure how much oil drains out of the old compressor and replace with just that amount.

©, 2015 Rick Muscoplat

Posted on by Rick Muscoplat



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