Synthetic oils maintain viscosity longer than regular oils.
I have used various oils in my Celica GTS for 20 years with 350K miles, as long as they are on sale cheap. Have seen no problems or differences between oils. Car runs smooth and strong pretty much like new, Cylinder compression about 220 now in all cylinders, close to new.
Over a few years I was busy and lazy, did not change oil, only adding and driving high speed on low oil. At 250K miles. Cyl 1 and 2 lost compression, 190 200 210 230. Engine idled rough. Shops said internal engine wears, could not fix, had to swap in reman engine $5000. I troubleshoot, added GUMOUIT in cylinders, soaked them over night, revved up engine next day, exhaust pumped out lots of white smoke, evidence of burned varnish on pistons, rings and valves. .Compression restored to 215 220 224 225. Engine ran smooth again. I further flushed engine to clean out internal varnish with MOTOR MEDIC GUNK. Dumped oil was black and thick like tar. Valve head was clean and shiny after flush, no sign of any varnish or sludge.
I use Walmart SuperTech full synthetic 5-30 or 10-30, supposedly guaranteed for 20K miles, about $25 for 5 quarts, probably the cheapest oil. Engine runs smooth and strong, very little oil loss, like half quart, between 10K to 15K change intervals.
if your engine is over 100K, suggest you flush engine with the oil change. I flush with half strength GUNK every oil change to keep engine clean of deposits and sludge.
Last edited by CAPTAINSOLO; Oct 1, 2022 8:42pm.
