Personal preference...
I used Castrol 20W50 in all my vehicles for many years--changed to 10w30 in the winter...never had an engine problem...
Then I quit my job to work on my own,and money wasn't so plentiful--and my trucks sat more than they got driven for the most part...I started using Wal-Mart "Tech 2000" brand cheap oil,probably made by Quaker State or some other big brand name...I havent had any problems with them running the cheap stuff--but again,I dont drive long distances or even go far at all anymore lately...had I been using them to do the 130 mile commute to work each day like I did in years past- ,things might have been different..
I think its most important to change oil often,rather than what brand----I usually have to drop the oilpan,and replace the timing chain and gears and oil pump in most of my trucks after I get them(I put motors in most of them)--,and if I see lots of sludge,I just run cheaper oil...but 99% of my engines looked nice and clean inside,so I now use the 15W40 diesel oil I buy in 2 gallon bulk jugs from Wal-Mart,or a local heavy truck supply place in ALL my engines,gas or diesel..its cheaper in bulk,and better oil to boot..
It keeps the motor much cleaner than regular oil,and I notice if the motor uses a bit of oil between changes,it uses less of the 15W40 than even 20W50 for some reason (probably a higher "flash point" on the diesel oil)...I also change the filter EVERY time,and I used to use the 2qt filters--but I felt they were overkill for a normal street driven truck--if I towed or it was 100 degrees all summer here,I'd use the 2qt. filters..(extra qt.of oil,and the big filter helps cool the oil--but its overkill for my needs)..
I think synthetic is too costly,and unessasary in older trucks driven on the street..I dont trust mixing synthetic in with whatever its been run on for years!--I fear sludge getting loosened up and passing thru everything--and they say synthetic will leak more and burn more than dinosour oil,if your motor uses oil....I'd use it in a newer vehicle with low mileage--IF I had the money too!--but "regular" oil is pretty good nowadays..its good enough for my trucks..again,if I towed or drove my truck hard,then perhaps I'd consider synthetic oil...Right now I can hardly afford the "cheap stuff"..
P.S.--I dont trust many of the "miracle" oils like Prolong,Slick 50, etc--only car I used Slick 50 in had noisy lifters from that day on!--and it ate a cam lobe shortly thereafter...I did use "Tufoil" and did notice a bit more power and gas milage in my van--but the 250 six had noisy lifters too,dont know if I can blame the teflon in the tufoil for that..I'd only add Lucas motor treatmemt or "Motor Medic" to an engine that needs thicker oil to survive..I dont believe in ads for stuff you can drain your oil out,and drive 500 miles with no damage!

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