Quote:

Quote:

One bottle of STP treats 5 qts. of oil. My system, 7 Qt. pan, windage tray =1 more qt. and an
HP oil filter = 1 more qt. That's 9 qts, and I just add another bottle for GP's. You can't have too much zinc.

I am not saying STP is bad, but remember that the oil in the STP bottle that carries the additives may not be the best oil.



As a matter of fact, you CAN also have too much zinc in the motor oil. Too much zinc increases the formation of sludge and pitting of metal surfaces.

STP is also containing additive called Viscosity Modifier and they are polymers. By using an additional STP bottle, you are also pouring more plastics to the crankcase. Certain aftermarket oil additives are also containing chlorinated paraffin that one type of an active chemical ingredient. It is causing bearing weight loss. The lubricant industry is using a bench test ASTM D5119 to evaluate an oil's ability to control copper/lead/tin corrosion of bearings. Using aftermarket additives you most often improve the chemical corrosion of the bearings. Read the attached pdf file copied from a lubricants professional journal a few years ago

The US Federal Trade Commission has had a few cases against aftermarket motor oil additive sellers

STP Engine Treatment
http://www.ftc.gov/opa/1995/12/stp.shtm

Valvoline Engine Treatment
http://www.ftc.gov/opa/1997/10/valve.shtm

Slick 50 Engine Treatment
http://www.ftc.gov/opa/1996/07/slick.shtm

Dura Lube Super Engine Treatment
http://www.ftc.gov/opa/1999/05/duralub2.shtm

Motor Up Engine Treatment
http://www.ftc.gov/opa/1999/04/motorup5.shtm

Prolong Super Lubricants
http://www.ftc.gov/opa/1999/09/prolong.shtm

Make your own conclusions from the above, but as a lubricants professional and formulator of lubes I would prefer to use high quality lubes instead of making own mixtures with aftermarket additives. You can't necessarily improve an oil by pouring in more additives from an expensive little bottle. As a matter of fact, you even can make things worse. Overdosing STP may not have been the one and only reason for the spun rod bearings, but sure it has had it's own negative reactions to the motor oil