All A/C compressors need to be lubricated in some way, whether they’re pumping freon or air. Most compressors are lubricated by the liquid freon that they pump. The York, on the other hand, has a separate oil reservoir that it uses to lubricate itself. This is the primary reason that York compressors are so popular for onboard air setups.

Non-York Compressors

Most compressors require oil to be injected into the air intake with an inline oiler available from any air tool supplier. After passing through the compressor, the oil is then filtered out of the air supply on the exhaust line before it reaches your tank or tires. Most air tool suppliers should carry oil/water separators. Some separators also have a drain that will allow plumbing the filtered oil back into the oiler intake, which eliminates the need to manually empty the separator and refill the oiler periodically.

York Compressors

The standard York has an oil fill/check hole in the center of each side of the compressor body. They’re plugged with a bolt with a 1/2″ hex head and sealed with a rubber O-ring. The York I got from a Ford had one of those holes permanently plugged (that side was unreachable in the factory mounting location), so only the right side hole was usable. When fully filled, a York used as an air (not A/C) compressor requires 8-10 ounces (237-296 mL) of oil. The type of oil isn’t critical when pumping plain air w/o freon; regular old 10W30 or ATF will work fine (I used ATF). A trigger-type oil squirt can seems to be the best way to add oil when necessary. To check the oil level, I recommend using a dip stick as described on page 7 of this section of the York service manual. It’s a PDF file, so you’ll need to have Adobe’s Acrobat Reader installed in order to view the file. You’ll need to rotate the crankshaft to get the crank journals out of the way of the dip stick. When using the right side fill hole like I am, you want the crank’s woodruff key to point upward.

[ I’ll be updating this page eventually with updated info. Until then, check out the York oiling modification page. ]

The oil fill/check hole on a York is on the left side (as the compressor sits upright with the pulley facing you), about half way up the side. It’s plugged by a standard 1/2″ hex-head bolt. Nick Leiterman quoted from the International Harvester truck service manual for the ’78-’80 Scout II:

The compressor can be operated in any position from horizontal left to horizontal right. It can be operated clockwise or counterclockwise.

The manual describes how to make your own dipstick. It recommends making it from 1/8″ steel rod. For horizontal mounting, it’s just a straight piece, because the filler hole is at the top. For vertical mounting, it’s bent to a 78 degree arc with a 4-3/4″ radius, with a 1-1/2″ straight section on one end and a loop for a handle on the other end. Most people approximate this design with a bent coat hanger. The manual also says you may need to rotate the compressor crank shaft slightly to permit entrance of the dipstick.