I have a little 25L Draper compressor in the garage, 2HP 240V thing. I lent it to somebody for a while and they said it kept tripping out (overheat) on sustained use and I now find that there is next to no oil in the compressor unit...

I have never ever had to top one up before - others I have used never ever lost any hence the fact it has not been checked for, er, probably quite a while

So what sort of oil should you use in a small compressor like this?

The only oil I can find locally in a quick inspection after lunch, is a Clarke "compressor oil" which on close inspection of the small print on the bottle looks like being a straight SAE40 engine oil. The book for the compressor has long since departed and I can't find anything helpful on Google which just wants to tell me how many different oil-free compressors Draper make haven't come up with anything on here either.

Any thoughts please? Is it critical or do they all use pretty much the same? I hope the compressor itself isn't f**ed as it sounds to have trouble starting when there is over about 50psi in the receiver, and it used to just spring into life immediately, but I hope that having the correct oil level in it will help! It sounds fine once it is running though.

Is "air tool oil" the same stuff? I already have some of this at home but maybe it is completely different stuff to the oil for the main unit?

Ta

What's in the tank shouldn't matter, as the pressure switch should dump the pump outlet to atmosphere when the tank is up to pressure, allowing the compressor to start with no (minimal) load on it next time.

The SAE40 compressor oil i have is much thicker than the air line oil i have.

Its one of these or a near equivalent model

http://www.justoffbase.co.uk/Air-Compresso...Draper-DA25-230

Must admit I was switching it on and off not waiting till it had filled to working pressure and tripped off, so maybe that was why. When I bottom out what sort of juice it needs I'll check it again, though I know our big 270L workshop compressor at work chugs a bit when it starts up with air in the tank. Maybe that isn't working properly then! It's done that for the twelve years I have been here though.

Boggy - I use SAE40 compressor oil.

I don't think airline oil is the same thing - I wouldn't put tool oil in the compressor, unless it was an emergency(!)

Al

If you used the plunger on the top of the pressure switch to turn it on and off, that would have dumped the air, if it's working correctly.

if you turned it off at the plug, the fill pipe would have remained at pressure, which would cause the pump to start under load.

Cheers Al - so you reckon the Clarke SAE40 would be OK then?

Mental note to self to check more often than when I bought it and never again

Seems happy on the SAE40 engine oil, thanks folks

the diesel driven compressors we used to use for shotblasting used hydraulic oil in the hydrovane compressor i have a clarke comp at home and i put hydraulic oil in this chris

Hmm having used it for a while it still seems to have trouble starting even from the same starting pressure as its always used. Not sure if this is down to the oil or the fact it ran without oil for a while.

Ho hum, better budget for a new one some time then

Note to self: do not lend expensive items of workshop equipment to people

mine has the same prob as yours if i use it with an extension lead ,prob the amps it draws on start up as it has no soft start ,chris

Mine is plugged into the same socket it has always been powered from but only started doing this after I lent it out