Toyota Repair: Losing oil without an oil spot in the parking space, 1991 toyota tercel, toyota tercel

Question
Hello!
I have a 1991 Toyota Tercel automatic transmission car with just over
55,000 total miles. I'm the original owner and due to a disability I drive it
mostly short distances. Just over two years ago I had some regular
maintenance work done. I was informed when I went to pick it up that they
had 'replaced' the head gasket. They also replaced the freon in te A/C
and when I questioned why the work was done without telling me first, he
said it was needed. I couldn't debate the need for a head gasket because
I have limited understanding of most of the engine. I was concerned when
he said the freon needed replacement each year because it gets "gunky."
I asked how a gas in aclosed system got gunky and he asked if I was
saying he lied. I said unless he could show me in a book about this
maintainance that I wouldn't pay. I lost the gasket battle. Now I am having
to add oil (the best I can recall) every four months or so or the oil light
goes on. There is no obvious signs of oil leaking and I have a personal
parking space where I live. I have noticed 'smoke' coming from the
exhaust pipe, especially when I first turn it on when it has been sitting over
night at least. I cannot tell if it happens when I turn it on after that when
coming home but I think I smell it. It isn't as dramatic when I look in my
mirrors. I just had it inspected teetered and it passed the exhaust test for
TX requirement. (I was asked to pay first making me wonder how they
knew the car would pass.)  Obviously something is wrong and honestly, I
don't trust taking my car to someone without being able to ask appropriate
questions or recognizing if I am being taken advantage of. That has
occurred in the past at the dealers repair division. I also do not have a
trustworthy mechanic…I guess that is obvious!  What do you believe is
wrong and is it real bad and potentially costly? Thank you for your time
and have a nice holiday season.  

Answer
In most states, including Texas, it's against the law to do any repair work without customers prior authorization, no matter if it's "needed" or not but that's in the past and not much you can do about that now, I have problems with any mechanic that refuses to explaing why a repair or maintenance procedure is needed, at that point all credibility is gone.  I understand that it's not easy anymore to find someone really trustworthy, I get horror stories online all the time. The a/c system needs no attention unless it stops working, if there is a leak then it should be fixed but if there is no leak the freon should not leak out at all and no annual maintenance is required.
The oil usage on your tercel is probably due to leaking valve stem seals, this is common on these engines, there is usually blue smoke from the exhaust right after starting it in the morning and then goes away, the solution is to replace the valve seals, this can be done without removing the cylinder head. Unfortunately this is very labor intensive and can run close to $1,000 at the dealer. Best of luck to you.