Originally Posted By: mongo161
IMO.....If the filter is in "By Pass" mode.....the filter will stop very little if nothing at all. IMO....Most vehicles are in the by-pass mode on start up and some are in by-pass mode until the engine and oil reach operating temps. Hard Drives.
Mongo, I think you are under some misapprehensions about bypass operation.
Indeed, cold starts are the most likely time for bypass but it isn't a given if you run the correct oil viscosity and keep the revs low while the oil is warming up. And bypass isn't a full open or full shut deal. The valve opens by degrees according to DP (differential pressure). If the valve cracking pressure is 8 psi and the DP reaches 8.5 psi, then the valve will open a tiny bit. Most of the oil is still flowing thru the filter but the overpressure is flowing past.
Bypass is usually a fairly momentary period. The valve pops briefly. Also most oil in most engines is relatively clean (look at an average UOA and see), so a little bypassed oil is not a problem in the big picture.
How much the valve opens is directly related to DP. Most oil filter spec sheets list only the full open spec. Puro, to their credit, lists a range, in which the low number is the valve cracking pressure and the high is the full open.
The filter on my F150 is rated at 8-16 psi. I have a differential pressure gauge on my F150, and have been monitoring the gauges for 10K miles and nearly 2 years. Even though my engine has 10W30 oil (rated for 5W20) and gets cold started in a winter climate (NW Ohio), bypass events are few. Even fewer if I work hard at keeping the revs low when the oil is cold. With the 10W30, once the oil reaches 150-160F, I have very little chance of reaching bypass unless I rev up to 5,000 rpm. BTW, the filter has 15,000 miles on it.
A typical cold start, when the engine flares for cat light-off, I might see 6-8 psi... right up against the cracking pressure. As soon as the engine comes down to idle, it drops way down to 4-5 psi. Driving off, If stay below 3000 rpm, DP never reaches 8 psi and by the time oil temp makes it to 185 or so, DP is 2-4 psi depending on the rpm. Again, that's with a filter that has 15K miles and oil that is at least one grade thicker than spec'ed (that is a test). Thinner oil and a less loaded fiterl would equate to lower DP. I am due for an oil change now and 5W20 is going back in, as will a new oil filter, and we'll see how the baseline changes. DP should drop a LOT! Once I have a baseline with a new MC filter and 5W20, I have a stack of filters I was sent to test for DP with the filter in a new state.
As to magnets, I suspect they work but I have not seen any data to show what we are getting for our money. Lots of money. UOAs are inconclusive... the iron doesn't change much at all and neither does a particle count. I have magnets on a couple of my tractors and the before and after UOAs and particle counts were inconclusive. Much of what I have seen elsewhere is also inconclusive in that regard.
My thinking is that what the magnet is catching and makes for such whizbang advertising images is the mostly the same stuff the filter would catch normally. Yes, magnets can get very small and submicronic particles as well, but the smallest particles have little effect on engine wear.
The magnets do have an effect on filter life. Every particle the magnet catches is one pore in the media that won't get blocked. Not sure if that's worth the money in most cases.
I think the best venue for these things is an engine that naturally sheds a lot of iron, such as an old school flat tappet engine and/or engines with Morse chains. A Chevy smallblock for example. Some diesels. Many modern engines use roller cams or rockers, which shed very little metal, and they use external timing belts instead of internal chains, so their iron contamination is very much lower. That would significantly reduce the benefit of having the magnet and detract from the ROI
