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The Land Rover LR3 service manual specifies:

Compressor oil : Denso ND-8 PAG oil

I'm scratching my head trying to figure out whether the following oil, which seems equivalent to ISO VG 32 would do as a substitute. The A/C shop selling it says that this is what most customers use for R134a applications:

Suiso SL 32

Based on this chart, it looks like the oil should work with piston compressors designed for R134a, but ...

... According to Denso, ND-8 is equivalent to PAG 46, which would suggest that the viscosity isn't what it should be:

Denso Chart

  • So, why not contact the experts at Suniso - big button on lhs when I clicked on your image... – Solar Mike May 12 '18 at 20:37
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If it says Denso ND8, you need Denso ND8 (ND oil 8). I would tell you that what you need is nothing but PAG oil of ISO 46 VG viscosity grade, known as PAG 46 (be careful: PAG 46, not PAG46 YF, which is meant for R1234 refrigerant and contains a different additive package), but, if you want to be 100% sure, make sure that only original Denso ND8 oil makes it into your system (no equivalent products, only the original one).

Be careful with oil viscosities. If your compressor is rated for ISO 46 VG oil then lubing it with ISO 32 VG oil isn't a smart idea.

In addition, Suniso SL32 is an ester oil, while what your system needs is PAG oil (careful how you handle these oils because, if you're not using Double End Capped PAG oil, they're both hygroscopic). PAG and ester is different chemistry and if the compressor is meant for PAG oil and not ester there's a reason, and this reason is that the compressor is designed for the kind of lubrication provided by a certain oil viscosity and chemistry, so, again, be very careful about what A/C shops tell you. Ester oil is known as POE and POE, except for electric driven compressors and applications meant to convert R12 systems into R134A ones, is mostly used only in buses and coaches featuring very large AC systems and compressors (mostly V piston designs).

Definitely, Suniso SL32 is a big no no, in my own opinion. You would be using a lubricant oil not designed for your compressor. One with a different viscosity grade and a different chemistry.

In addition, remember that if you want to replace your system's oil you need, in addition to removing the compressor and draining any leftover oil from it, to flush the system of any remaining oil (and replace parts which can't be flushed, such as parallel flow condensers, receiver driers and TXVs), the oil needs to be balanced across the system so that the compressor neither seizes due to lack of oil nor it gets slugged during the startup, and the startup has to be done in a particular way. If you're only replacing your compressor without doing any system flush (not recommended) then you only need to measure and replace any oil found inside the compressor and, again, you need to circulate any oil left inside the compressor (so that the reed valves won't get damaged by oil slugging) and then be careful about how the compressor is started up for the first time after this operation. These procedures, however, are best left to trained and licensed professionals, because the risk of compressor and system damage is very high, and handling refrigerants with dedicated recovery stations is always the best choice.

  • Thanks for the detailed answer. I am interested to know why you say that ISO VG 32 is a poor substitute for ISO VG 46. From what I can gather VG 32 has a lower viscosity, which isn't necessarily a bad thing from a mechanical perspective unless a certain oil film strength/thickness needs to be maintained – Zaid May 13 '18 at 10:33
  • Whoever designed your compressor intended it to have a certain lubrication at certain temperatures and has successfully tested it with a certain type and viscosity of oil. By using a different oil chemistry and viscosity you're lubricating the compressor in a way that is different from the one that the designer expected so you don't know if your compressor will overheat and seize or not. And i suppose that your purpose is not doing research on a batch of AC compressors, but having one compressor reliably cool your car. So you don't want to accept the chance of a lubrication failure. – Al_ May 13 '18 at 10:40
  • Just as a follow-up, I found a shop selling both Denso ND8 and PAG 46. The former was 5 times the price of the latter! I ended up going for the PAG 46. – Zaid May 30 '18 at 6:38
  • I hope it was double end capped PAG46 at least (if not, let it catch as little air as possible!). For peace of mind, if i were you i would have spent my money on ND8. You know, a seized compressor is much more money. – Al_ May 30 '18 at 9:40
  • @Zaid Out of curiosity, how is it going with the PAG 46? – Al_ Jul 21 '18 at 18:06

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