I would change the battery cables grounds form the battery.
As well as making sure the alternator is producing 14 volts at shut down otherwise they seem to kill the battery easy.
Get a new mechanic.
If after replacing the second so shortly he should have diagnoised it properly befoer letting you leave with another alternator.
Sounds like a wiring problem. CHeck your grounds and how good your battery is.
you have 3 sensors 2 on the engine are the same the one after is slightly different.
You may have had one changed before and they may have cut and spliced a new harness on.
Get someoen to look at what the particles are then make a judment.
A new engine can be easily attained for less than 5000 installed to add another 10 years of life
As am i , nice to see a oil thread with everyone on the same line.
Mobil 1 is basic protection while redline ,royal purple and motul are much higher end ones.
Don't they have high mileage synthetics?
High mileage oils usually just have more seal conditioners and viscosity thickeners which can be done with any oil including synthetics.
It would be cheaper to get your refinished than buy new stock ones.
Your stock ones as any 95 and newer LS has a higher X factor to be able to clear big brakes. Thus they have a higher price tag so 4-600 would be hard to get in good condition.
After so many years ,i have finally learned what the damn strut rod is .
Now i have to go and change mine as i was never sure exactly how it figured into everything.
Just to clarify .
Tanabe is Greddy's Japanese trade name which is more well known states side. A greddy dealer is much easier to find as there are no Tanabe dealers here.