I have an Elna Carina SU 66.
A good resource for all things Elna is found on groups.yahoo.com.
Yahoo group elnaheirloomsewingmachines will answer many of your questions. Most of the people in this group are experienced Elna mechanics or collectors.
I doubt that the problem with your machine is that it needed oil. While it might need oil, if it stopped, or won't form stitches anymore, it is more likely that it needs a gear replaced or some other mechanical adjustment.
I purchased my Carina in 1983 and recently had it factory serviced by Elna. Contact email@example.com
for a dealer close to you to get yours repaired. It will cost under a $100 plus parts. Considering what new machines cost these days, it is well worth the investment. If you don't know what you are doing, you can cause further damage. These are quality machines. Newer models can't come close to the stitch quality.
BTW, any of those sewing machine oils will be perfectly okay in your Air Electronic.....If your machine did not come with it's original manual, there are plenty of places online where you can get one for a few dollars. It will show you how to oil the machine. It only needs a tiny drop in one particular location on the bobbin case. This machine does not need every nook and cranny drenched in oil. One drop...in one little location...that's all.