Hello.....Have watched this site with great interest and have learned MUCH. I thought I knew oil 'till I came here. I have been using Shell Rotella T 15-40 conventional in all my vehicles over the last several years with no problems. I tend to have high milers, as I am a decent mechanic, and like to save $$ for my other interests, as opposed to big car payments. I recently was able to buy out a bunch of Castrol Syntec 5-50 for 5 bucks a gallon. I put it in my high mileage Ford Truck, and also in my 550 hp 440 mopar street/strip car. Since buying the Syntec, I have read some unsavory stuff about it on this site. I got it so cheap, and I have about 20 gallons of it, should I be concerned. I don't mind changing my oil often, and I have WIX master installer filter status, so I get my filters for about $3 each, so my cost for an oil change is about $9 in my truck, $8 in my minivan, and still only $15 in my 10 quart holding 63 Dodge. Should I use the stuff up, or is this stuff so bad should I get rid of it?? The Old Dodge is a Michigan Summer car that sees 90% street-10% strip duty, that I shift at 6200 RPM. I change the oil in the 63 every 300 miles, or after a really hard day at the strip. Is Syntec really poor oil, or is it a poor oil for the $$, or just not as good a synthetic compared to Mobil 1, Amsoil, Schaeffers, etc.., but still a fair oil compared to most conventionals, etc.. HOW BAD IS THIS STUFF????? At $5 per gallon, would you use it??