Currently i'am running an air compressor with shell corena p100, is it adviseable to use caltex RPM compressor 100? What factors should i be interested in when considering if oils can be mixed.

Cheers

Some factors that I would consider are: 1. The ISO VG of the two types of oil(in this case it seems to be 100) 2. The type of base oil used (I checked out both types and noticed that Shell corena P100 is a Naphthenic and The Caltex RPM oil is a Paraffinic blend) 3. Check into the additive package of both oils to see if they are comparable. I would also recommend sampling the new oil if you decide to go with it. Sometimes certain batches of new oil differ enough to cause a significant change after mixing the two oils. Your oil supplier should be able to tell you if the two types of oil are compatible.

Intel Inside,
I have tried mixing oils, and greases, that were supposedly compatible according to the supplier. On two occasions it led to disaster. There was one small item within the oils that the supplier must have overlooked. The grease episode cost over ten grand. Ever since that time I have insisted that the two fluids be tested for compatability. Having them tested is the only sure way to determine if they can be mixed with no problems. The minor cost upfront is well worth the piece of mind later on, not to mention the savings by avoiding a potential disaster.

My personal recomendation is to NOT mix diferent oils. If you do not have another choice, in addition of what Pinkston posted, I sugest prepare 5 diferent mix samples and evaluate it in the lab. The 1st one 20% oil A and 80% oil B, the 2nd one 40-60, 3rd 50-50, 4th 60-40 and 5th 80-20. This will give you a better idea on what is going to happen in the system.
Once again, my recomendation is to NOT mix diferent oils.

The previous owner interchanged between the following oils:

Shell Corena P100
Caltex RPM Compressor 100
Castrol PD 100

However they were having issues with oil consumption and crankcases blowing up. Is this a possibility when mixing oils?

I have also talked to a Caltex technician and he indicated that it should be ok to mix them, however lab tests would need to be conducted to be sure (6 months at least).

Are there any websites or technical information available that might act as a rough guide for compatible mixing.

Mixing is not a great idea, unless you have a crisis. If sumps are small simple drain the oil and fill in the new grade.

From the details provided by Pinkston, Shell Corena is napthenic in nature and is in a probability, a refrigerating compressor oil. Caltex product may not be for refrigerating compressors, similiarly Castrol Aircol PD is for use in compressors other than refrigeration.

Ref compressor oils will need to have low pour and low floc point values and base oil preferably napthenic in nature. However, additive packages will be less or low in such cases.

Suggest you go into the history as to why Corena was recomended/used in the first place.

Hussam Adeni

My preference is to change out the oils completely. Napthenic oils, as stated are usually used in freon-type compressors, and are still used in some Ammonia systems even though Group II Ammonia oils provide better performance. The napthenic oils normally have such a low VI that they thin out too much in the high temp zones of the compressor. Aside from basic compatability, you should consider two other items:
1. Are both oils either acidic in nature or basic? If one is basic and the other acidic, in the presence of moisture (from compresion of the air) you will get additive precipitacion.
2. Seals: Naphtenic oils will generally swell seals more than paraffinic oils due to their hier content of aromatic hydrocarbons. In ASTM D 471 tests:
Buna-N seals will generally expand 1.3% in Napthenic, contract 3.6% in Paraffinic, contracting 4.2% when paraffinic is used after naphthenic.
Neoprene seals swell 45.2% in Naphthenic, but only 5.4% in Paraffinic, contracting 15.1% when changing from Napthenic to paraffinic.
The Neoprene seals soften 5.2% in paraffinic, 32.7 % in Napthenic, but harden 22% when replacing naphthenic with parafinnic.
--SO I believe the best time to get rid of Napthenic oils is when you change out the oils and can replace the seals.

I would be considering if the oil viscosity is compatable, other factors also to consider would be are the viscosity grades the same.
Are the additives in both oils the same or compatible.
The mixing of oils where possible should be avoided, contact your lube supplier for compatability, or seek lab results to put your mind at rest and save $$$.

What affect would adding MoS2 (Molybdenum Disulfide) to any of these type of oils have. How long would it be effective for?

Thanks All the posts so far have been very informative