1993 Infiniti G20 • 22,700 miles

I know my car is old, but I need it to last me at least another year. I have had lots of work done on it through out the years. Just a few days ago the oil light starting coming on, then the car starting surging when I shifted gears. I went to the auto part store, the guys checked my oil & it was 2 Qts. Low. I put the oil in, it seems better, the light turned off, but it seems like it is still surging a bit. I am getting the oil changed tomorrow, but was wondering what causes the surging.
Also when I first put the car into gear it rumbles before it takes off, while it is driving and idling, the engine is very quiet. Any ideas?
p.S. I know it's my bad for not checking the oil, I Just got use to looking at the sticker for the date, or month, & my mechanic that did the tune up did not put a sticker on the car for the oil, he said he changed the oil & checked all fluids. Going to my regular guy for an oil change tomorrow.
January 29, 2013.

Do you have any check engine lights? Have your mechanic pull the codes and see what is wrong with the car. Also, he could probably go for a test ride with you which would be a lot better then me trying to diagnose what is wrong with your car over the internet. If he can give you some ideas of what might be wrong, I could point you in a direction of how to take care of it in the most economical way.

Jan 30, 2013.