air compressor doesnt like cold weather

MY air compressor doesnt like cold weather. This morning ,it was about 40 degs, I had to put a heat lamp on it to get it to start. Kinda annoying. Is there a winter cold weather compressor oil? I see a lot of it is 30 weight non-detertgent. Any ideas?

Thanks I will try that :)

I use SAE20W non detergent year round in my compressors and haven't had any problems. They are all Quincy industrial and pressure fed lubrication.

What tom said about the unloader... moisture or oil residue in the unloader... or anything causing the outlet check valve to stick, will make for a difficult cold start.

I've used all sorts of oils in my compressors, and i've worked with many oils on the reciprocating and rotary screw locomotive compressors i taught on... and i've had plenty of discussions with a buddy who was a service techninian and later an engineer with Ingersoll's industrial compressor group.

from this, I've come to these conclusions:

1) ANY oil is better than NO oil.
2)Clean oil is better than Dirty oil
3) Moisture in compressor sumps is both problematic, and inevietable.
5) Automotive detergents will tend to act as surfactants, suspending crud and moisture, and forcing then up into the workings, rather than allowing them to precipitate and settle into the sump...
6) detergent and viscosity altering additives frequently separate out, and become lighter fractions that partially combust under compression, leaving carbon residue on the valve leaves.

Now... that tends to favor non-detergent oils... and many older compressors were spec'd for straight weight non detergent motor oils, because they were very common 50+ years ago, and many of the compressors then, were mobile units built following a government spec for tactical (combat) service, where the machine's expected service life was not decades or years, but rather, a week or three, ended not by failure, but by the introduction of copper-jacketed projectiles...

Now, there's two classes of'compressor oil' available... the first type is in the big box store labeled 'Compressor Oil'...

then there's the stuff you find at the industrial-type places frequented by steel-toe'd customers...

and there's a couple noticeable differences. The former has a 'brand name' that matches three house-dominant supply of imported sockets and screwdrivers, and comes in a half-pint bottle. the latter has a name of a major petroleum company, comes in a one or two gallon jug, a 5 gallon bucket, or 55 gallon drum, and the per-unit cost is about 5 times' that of the big box brand.   

I'm not gonna say that the big box house brand is 'bad', but i will suggest that there's a significant difference in the target market...
Industrial source is the only choice for someone who has four hundred-thousand-dollar compressors in action 24-7-365 keeping a manufacturing line running.

the big box source is there for a Joe Homeowner that has a few air tools and a tire chuck... where poor oil means he buys an new compressor every 5 years... which is about 800 hours of operation.

I run expensive stuff.   I get it from my industrial buddies, they buy the 55gal drum, and have a half gal leftover every 6-8months or so.

I usually don't change it all... i drain off the goo at three bottom, then restore it to level with new.

What you SHOULD watch for in your compressor, is RISING oil level... that happens because moisture is accumulating in the sump.

now, other things that cause hard starting, in a SINGLE PHASE motor, is a failing start capacitor. many will lose their quality as they reach their end of life.   open the covers, get the voltage and capacitance ratings, and order replacements. change them on an afternoon off...   

cold weather and a long history of dusty operating conditions can make the centrifugal start switch lazy. careful disassembly and cleaning is the long term solution, but pulling the plug and housing it down with some WD-40 will often wake them up.

Corroded wire and connections will limit start current... moisture in the atmosphere will be drawn into stranded wire by cappillary action, causing oxidization of the conductors deep inside the wire. if you feel the wire, and its warm, you've got a problem there... bypass the wire with a known good test wire to prove it out.

Choke her a little hey you never said electric or gas.

So, on serious compressors, the unloading scheme is simple. they'd a line coming out of the last compressor stage that goes to the tank.

at that point, is a check valve as noted above.
on that check valve fitting, directly ABOVE that check valve's poppet plate, is a port for small tube going to the automatic pressure switch.

On the pressure switch rocking plate is a tab that depresses what is essentially the core of a schraeder valve <like your car tire valve>. the schraeder valve is holding back pressure in that little line.

when the pressure switch diaphram is overcome by tank pressure, it acts on the rocking plate which simultaneously cuts off power to the motor, AND depresses the schraeder valve, exhausting air from the line between the pump outlet and the tank check valve.

By doing it right by the check valve, the pressure there falls very rapidly, assurring a secure seating of the check valve.

When tank pressure falls, the rockplate actuates three motor switch AND allows the schraeder valve to close, so outlet pressure builds and overcomes the tank check valve.

This scheme prevents tank pressure from holding against the pistons when trying to start, and prevents static cylinder head pressurefrom leaking past the piston rings, pressurizing the crankcase, and blowing out the crank seals.

the aspect that allows the compressor to come up to speed... is the volume of air space in the line between compressor last stage, and the tank check valve. if the last compressor stage's discharge plumbing volume is say... 1000ci, but the last cyl displacement is 20ci, then you'll have at LEAST 50 Compressor rotations until charged enough to see significant pressure.