Compressor oil

[Seadog]

Piston compressors run very hot (as do all compressors, I suppose). They will burn the additives. Put your hand on the cylinder head after a few minute's running

 

[premmington]

+1 I do the same, every couple of weeks or so depending on heavy use, will open the external drain valve and just run it steady for a while until its good and hot...

I declare you no fool

No they need to get hot - get the moisture out!

 

[northwest]

Yes, obviously any specialist compressor oil is bound to be expensive but I was talking about your run of the mill standard piston compressors which the OP mentioned.

That is fair comment.

 

[premmington]

That is fair comment.

Wet sump on a Reciprocating air head (piston pump) does not hold much oil at all - I would just buy the right stuff. I reckon a litre bottle would see any DIY pump two oil changes (not really sure of exact volume?).

Big rotary air heads with oil coolers hold a lot of oil - most have a metal oil filter that spins on like a car.

 

[8ob]

The head gasket went on my abac compressor a good few years ago, gave it a treat and changed the oil at the same time. That only got 10/40 because thats what is here and its still going strong, that said its not running all day every day.

Bob

 

[cheb]

Anyone tried running their compressor on Castrol R, just for the smell of course?

 

[chris pruteanu]

I would use a quality synthetic oil 5w40, 10w40 will do just fine...As for burning off the additives, i smell a rat, most petrol/diesel engine run as hot if not hotter than any compressor and to closer tolerances yet the live fine day after day... I have fully syn castrol edge 5w40 in my abac compressor, runs well, doesnt skip a beat and its working daily for a few hours ! Modern cars are putting their engines under tremenduous amounts of stress, their oils are designed to withstand cold climate as well as hot weather so a quality multigrade will do them a favor...

 

[Farside]

In black and white in the owner's handbook, my Italian compressor maker says to use a 5w40 synth car oil. If I really want to, I could buy some of their branded stuff, at four times the price.

 

[chris pruteanu]

Correct, and a car engine endures much higher shear forces than a compressor and much higher combustion chamber temperatures, the temperature guage only measures the oil after it has cooled in most engines and this is an average temperature.



Many now do, and this is becoming the norm in smaller compressors designed for DIY use.

Just imagine the thermal stress the oil is subjected in a 1.8T VAG engine, it has to cool red hot turbocharger from a high speed motorway/autobahn drive and it has to withstand many cold start cycles while keeping whatever carbon deposits it dislodges in suspension until it gets filtered by the paper media of the oil filter...No way a sae20 can be better than a decent quality multigrade synthetic oil hence why i always used good oil even in high mileage engines, it protects a lot better ! Now about 10 or 15 years ago i sent my late father a clarke 50L direct drive compressor, which has been run almost continuously for spraying cars and which was filled from me once with castrol 5w40 oil...Its still working fine although it doesnt gets much use lately as its 110v and i have a larger, more powerful compressor as a replacements. A few years ago i was chassing a non start issue (traced it to a faulty unloader brass valve) and took the head off to see if piston its worn ! Absolutely no carbon deposits although the reed valves had a bit of overspray in them and no wear whatsoever. The piston bore was in spec, no play in either conrod/crank or piston and everything looked as it should ! My opinion is against manufacturers specs and go with better quality oils if possible, one time i asked a bmw tech for a strainer on a zf 6hp gearbox and oil to do a gearbox oil change, his computer said that gearbox is filled for life ! I said that gearbox life will be a lot longer if i changed the oil ! How he laughed of me...now they con you into changing oils every 30k or so in their gearboxes...

 

[daleyd]

My understanding is that the reason behind using “plain” oil in compressors is that the detergents/additives in modern oils keep particles in suspension to aid in getting them through to oil filters, which oil compressors don’t have. Plain oil allows any particles drop out of suspension and settle in the bottom which is possibly more suited to a simple splash lube system without filters.

If it came down to it I wouldn’t be that bothered by putting a modern oil in my compressor, it would probably work just fine. It just happens that plain oil is what’s recommended and it’s cheap so that’s what goes in.

 

[Hopefuldave]

My understanding is that the reason behind using “plain” oil in compressors is that the detergents/additives in modern oils keep particles in suspension to aid in getting them through to oil filters, which oil compressors don’t have. Plain oil allows any particles drop out of suspension and settle in the bottom which is possibly more suited to a simple splash lube system without filters.

If it came down to it I wouldn’t be that bothered by putting a modern oil in my compressor, it would probably work just fine. It just happens that plain oil is what’s recommended and it’s cheap so that’s what goes in.

+1, beat me to it - also why you shouldn't use motor oil in lathes / mills etc which don't have filter cartridges (mine has pumped oil and a "magnetic filter" full of fine mesh which is fine enough for swarf, but not wear particles. and uses ISO5 which is damn thin - I use a 50:50 mix of ISO32 and paraffin).

Dave H. (the other one)

 

[daleyd]

+1, beat me to it - also why you shouldn't use motor oil in lathes / mills etc which don't have filter cartridges (mine has pumped oil and a "magnetic filter" full of fine mesh which is fine enough for swarf, but not wear particles. and uses ISO5 which is damn thin - I use a 50:50 mix of ISO32 and paraffin).

Dave H. (the other one)

Yeah I bought a tub of straight iso 32 for my lathe (denford) - so that’s what goes in the compressor too, and will be going in my mill gearbox. When I saw the sludge in the bottom of my lathe and mill gearboxes you can see why it may be better not to have stuff suspended in the oil, it was pretty manky!