I work at a Valvoline lube shop, and while we carry most major brands of oils, we recommend using Valvoline to customers that aren't sure (or don't care) what to use. Now, the company has us hang all these posters that preach how much better SynPower is than Mobil 1 ("...offers 4x BETTER wear protection than Mobil 1!"), and to use MaxLife (conventional or syn) in anything over 75k miles, but I'm not really one for harping on a product just because I have its logo on my hat. First of all, is SynPower really that much better than Mobil 1? What about Amsoil? We also carry a few varieties of Quaker State full-synthetics, and they all cost the same. Customers typically choose the Valvoline products because the company usually has a rebate going on ($15 mail-in rebate currently), but should I be recommending a different brand? Next, MaxLife. Now, everyone at the shop runs this in their vehicles, and we've all noticed marked improvements in rear main seal leaks (as have most customers). What kind of additives are responsible for this? Valvoline claims longer engine life, reduced deposits, and improved mileage. Is any of this attributable to it being a synthetic-conventional blend? In a related question, what advantage (if any) is there to running a blend like MaxLife or DuraBlend? Finally, like most oil change places, we set reminder stickers to 3k miles or three months, whichever comes first. Usually, only one in twenty customers come in under that time, which I don't really see a problem with. I'm under the assumption that the 3k/3 mos thing is to get people in four times a year (at least) as opposed to once or twice. My question is, with synthetics that can easily surpass that mileage, can a standard oil filter keep up with it?