Originally Posted by tom falco

tj that is correct The big Q had a problem with their VII chemicals. In truth it really was not their fault. One of their vendors sold them some Parifin wax VII additives and all hell broke loose. It has been corrected but the guys in the KNOW like us wont trust the oil any more and that is understandable. Hay sorry westman just one of those days. The reason we are having valve train noize is not known yet. Our Mobil rep will be in town during the week and he will see what is going on. Right now its a mistery to us but we confirmed it. Like you so rightly pointed out westman there should be no logical reason for it. But here is what we were told by the reps. Even with synthetics the VII spread should be as low as possible for the climate you drive in. All oils are flow tested and rated at O* and 212* Example a O-30 would flow at O when the temps are at O* and flow at 30 at 212* So if your oil temps are below 212 and they should be what is the viscosity?? its not 30 maybe only 25 at 150* oil temp. Remember multi weight oils are VARIABLE. So always try and stay with tight oil spreads. Example a O-30 at 106* is only a 15 but a 10 30 at 106*is a 20 vis. What happens the oils are viscosity temperature modified or STRETCHED. This is a good thing but it can wear out and stop doing that. That is what happened to Quaker. The VI kept on stretching to a massive number and turned to thick sludge. Think about it like a rubber band if you stretch it to farr and to long it breaks. Also diesel oils have more acid reducing chemicals than gas oils. This is because of the sulphur in diesel fuels. Now its a different story with low sulphur diesel fuels. Like i said oil is like socks we all wear them but they come in different colors. Also changing oil is the best solution for engine life. Basically the more you change it the better. (To some extent) Oil suspends dirt and no filter can remove all of it. Remember every oil system has a bypass valve that bypasses the filter from time to time. If the filter is to restrictive it bypasses. There again another balancing effect on an oil system. The best way to have good filtering is to increasing filter material surface area and micron flow(physically bigger filter or a filter with more pleats etc). The better the filter the easier it cloggs and bypasses. I did tests years ago with different micron rated filters and found out that to much filtering can and does open the bypass valve. Hope this helps Tom