Fo all you heavy for spec oil guys its interesting that Castrol seems to stick to that side of things. Check out the PDS for a few of the products they sell. This is all 5w20 but the 30 has the same affect right at the top end of the viscosity for spec chart. I have a small rear main seal leak and so far PHM has done the best and I attributed it to be slightly thicker or whatever you want to call it so when I noticed Magnetic at almost the top of the CST scale for a 5w20 I thought I might give it a try. for some reason I never hear much about Castrol on here. I have noticed it has started dropping off the shelves at walmart in my area so I guess its just not popular. I really like that they list all the details on spec and that the PDF sheets on their website are all up to date unlike other companies who seem to not care what the spec sheets say. I also noticed that the PQI has them tested very close to whats listed on the spec sheets unlike some others who are much further off.
Regular GTX http://msdspds.castrol.com/bpglis/FusionPDS.nsf/Files/2811CF6C9F4AF94880257EC60063ED84/$File/BPXE-A2ZRHH.pdf
GTX High Mileage
http://msdspds.castrol.com/bpglis/FusionPDS.nsf/Files/65CFC837B6CDD27980257DCE0053FD85/$File/BPXE-9TFCUW.pdf
GTX Magnetic
http://msdspds.castrol.com/bpglis/FusionPDS.nsf/Files/97892B537D9CB6DF80257D79006A17BD/$File/BPXE-9R7F67.pdf
Regular GTX http://msdspds.castrol.com/bpglis/FusionPDS.nsf/Files/2811CF6C9F4AF94880257EC60063ED84/$File/BPXE-A2ZRHH.pdf
GTX High Mileage
http://msdspds.castrol.com/bpglis/FusionPDS.nsf/Files/65CFC837B6CDD27980257DCE0053FD85/$File/BPXE-9TFCUW.pdf
GTX Magnetic
http://msdspds.castrol.com/bpglis/FusionPDS.nsf/Files/97892B537D9CB6DF80257D79006A17BD/$File/BPXE-9R7F67.pdf
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