Maybe you need a new belt?? Not sure, but maybe when it turns and heats up, it stretches just enough to make it sluggish? Time to take it to the "hospital".

I have used the same bottle of singer machine oil for the last 10+ years and have used oil and lub from my Singer 221 that was 80 yrs old and they were still good. I would say afterward, they sing like a singer.
I have also used the oil with no problem on older Kenmore's, Juki's, and Brother's with out a problem.
I hope this helps a bit. A lot of good information has come your way from so many others. If the oiling and simple maintenance doesn't work it may be time to take it in for a tuneup and see if something else is not right.

The goop is definitely lubricant - don’t remove it unless you replace it with fresh lubricant. Not sure about the grove in the picture. The vintage group should be able to tell you if that is normal or a problem.

Just be aware that it is important to use the type of sewing machine oil recommended for your machine...there are different types. Ideally it would be good if you could find a reference for your machine and maybe under restoration. I have read that sometimes older machines need to be "cleaned" with one type and then have another type applied....I am not a sewing machine repair person. Just know you have to use the specific type of oil for your machine. Sewing machine oil can get old. I had a bottle that turned from clear to yellow and got a little bit cloudy....I tossed it.

Has anyone noticed this post is from 2012?
Brands of sewing machine oil are not different unless they contain additives like tri-flow. Sewing machine oil is about the same viscosity and refinement as gun oil. Sewing machine oil is sewing machine oil.

bkay

I attended a long-arm class in a quilt show a couple years ago. The instructor was a machine repair & maintenance fellow for machines, large and small, and noted quite a few areas that can easily get overlooked and which can give you tension fits, etc. if ignored.

Among the many items he mentioned was that of using ..oil. He said the test is the color. Good (new, fresh) sewing machine oil will be almost clear. As it ages, it begins to turn yellow. The ..oil will get gummy pretty fast and not do your machine(s) any favors.

I immediately checked my oil when I got home and, sure enough, I had a couple that were yellow and one that I had purchased fairly recently. It was crystal clear.

I've tried to watch it since then and my machines (including a couple decades-old Kenmores) just purr. In fact, they're much quieter than the newer machines.

Hope this helps. Happy quilting!

Jo Belmont- I just read the same thing. I just don't remember where!

Lots of good tips here. I don't have anything new to add, but I agree that it might be the gears. Look in the gears and see if there are any hard particles that are jamming them up. You may have to clean the gears and replace with fresh lubricant. The gears may be located in a couple of places...below the machine, or up in the arm.

I also second throwing away any old oil you might have and buying new. It does lose its viscosity over time. Check your manual to see what kind of oil they recommend.

The loose belt idea was a good one and also a possibility.

~ C

My research indicates sewing machine oil should only be kept 5 years. Oil found in old machines should not be used. I understand it breaks down chemically after too long.