Veteran & Classic Car Club of W.A.

Air Compressor Oil

  • 22 Jul 2022 5:07 PM
    Message # 12857294

    Stuck in the shed on another rainy day my thoughts drifted onto a bit of  maintenance on a couple of compressors I had been using (and then pushing down the back out of sight). Problem was which oil to get to do the oil changes. The paperwork said the old Arlec (yes they did make compressors last century) needed 15w40 synthetic but the newer Black Cat needed 5w50 synthetic.  I made the mistake of contacting a Compressor joint who said ISO68 was the go and couldn't translate that into my speak of engine oil specification. Do I just buy two different synthetic engine oils or some "special" compressor oil or just have a Bex and a lie down. Warren.

  • 23 Jul 2022 2:10 PM
    Reply # 12858452 on 12857294
    Anonymous member (Administrator)

    Hi Warren, As they say, oils ain't oils. I assume we are talking reciprocating compressors here. You do not want detergents in your compressor sump so generally most engine oils are not suitable. No combustion going on so you don't need or want detergents removing things. Synthetic oils  are "cleaner" having low levels of sulphur and carbon so you don't get these precipitating on the valve gear of the compressor. Bear in mind you will also get some carry over into the compressed air so you can end up with precipitation of things like sulphur in your regulators when the pressure is dropped.  Low foaming is highly desirable also.  Compressors tend to operate at high temperatures when used extensively  - they are air cooled so have limited ability to stay cool in hot weather and Charles' law says they are generating lots of heat internally. Hence the higher the top end weight number the better to maintain lubrication.  A low ish weight for your multigrade is nice when the machine is cold.  If you have to use engine oil then the 5W50 synthetic is probably OK for home use but if the compressor is doing a lot of work I'd go for a purpose formulated compressor oil.  Hope this helps, otherwise perhaps two Bex and a longer lie down whilst you think about it.  Cheers. 

     

  • 24 Jul 2022 11:45 AM
    Reply # 12859090 on 12857294

    Hi Andrew, Yes oils ain't oils (as we were told on the old Castrol GTX ads on TV). The compressors in question are reciprocating as well as a little challenging when it comes to this oil thing. Am going to go whole hog and buy some for purpose compressor oil (Penrite I think). All I have to do now is back off the Bex a bit..getting a bit twitchy. Thanks for the help. Warren.  

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