I am an amsoil dealer (just for myself) I like it but you do have to read the . fine print on oil change intervals, etc. type of filter (amsoil) or bypass filter system.
I switched over my van at 180k and did not have any oil leaks- but I did start using some oil about 1qt per 1000 miles- got 216k on it now and still runs strong.
1997 f250 4x4 sclb, auto, 3.55's, 191k, diy intake w 6637, ccv mod, pyro, boost, trans gauges, 3" dp to 4" single exh. super chips for now. scangauge
I've been running Amsoil dual by pass for years in my '95 Powerstroke and it works just fine. It is a little more troublesome to get their products, but overall I've been happy with the results. With dual by pass, I run 15K...change filters and send oil in for analysis, to date the analysis says to keep running, so I then run another 15K then change both filters and the oil, no matter if the analysis says it's ok, I just figure 30K is far enough and start from scratch again. Works for me, and has saved on alot of oil changes over the years, but I've never done a dollar for dollar research estimate, but I do know the oil stands the test of time, as the analysis keeps coming back as being "ok".
There tranny fluid ran like absolute dog crap in my brother's E4OD...To the point it was clunking and hot enough we pulled over and had the truck towed 90 miles home...Got home and replaced with some valvoline and has ran great (~1 year) since...I know i'll get a bunch of crap for it, but I think amsoil is a lot of hype
1997 F-250 - SCSB - ZF-5, 4x4, 4.10, 17* HPOP, Tymar Intake, TWildman Tunes, SD IC, 4" Straight Exhaust, Dana 60 w/ 3.5" RSK and SD Springs all around on 35" BFG A/Ts - SOLD
2009 - 6.4L - Crew Cab/Long Bed - FX4 - 4" Pure Performance X-Factor Lift - 325/60/20 Duratracs -- FOR SALE