I used this spread sheet to decide that Shell Rotella 5W40 Synthetic was an economical choice to use in my truck. Because of my driving conditions my owners manual indicates that I should change my oil every 3,000 miles. I believe that I can very safely run the synthetic 5,000 miles and my oil analysis bears this out. If you view the spread sheet below you will see that I actually save a couple of dollars annually by switching from dino to synthetic and going from 3 to 5 thousand mile oil change intervals. I do run a bypass but I suspect that the results would be the same with oem filtration. I believe that I get all the benefits of synthetic oil without any additional cost.
The issue of extended oil drains seems to excite folks on both sides of the issue. I am neither for or against extended oil drains. I do not run extended oil drains myself (unless one considers 5k an extended oil drain) but if I was going to consider extended oil drains this spread sheet would be how I would measured the cost benefit. I feel that extended oil drains are not worth the risk considering the relative cost of a tank full of diesel compared to changing my oil twice a year. To each his own though...
The Frantz setup I have cost $200 and they last decades so it should be the last one I ever need. I will move it from truck to truck to truck as I get new vehicles. I figure I will be willing/able to use it for the next 30-35 years. If I use it for 30 years and spread the cost over that period, it will cost me $6.67 per year to own. Now for the operational expenses. I change the TP every 5k and drive 12k per year. I buy the "expensive" TP from wefilterit for $1.56 per roll. I use 2.5 rolls per year, which means the "filters" cost me $3.90 annually. Of course I do use a little more oil due to what the bypass holds (about a quart per oci) so I use 2.5 extra quarts per year at $4.00 (Rotella syn and yes I know I am wasting money on the syn ) per quart. So extra oil usage costs $10 annually. Now if we total this up the bypass filter costs me $20.57 per year to own and operate. Another way to look at it would be that it costs me the same as 6 gallons of diesel or 1/6 of a tank of diesel on an annual basis. The bypass does have a cost but hardly impractical. I would imagine that over a period of 30 years the Frantz will save me quite a bit of wear. I would also imagine that the wear the bypass prevents will translate into tangible benefits. Now I know that it will be impossible to prove the derived benefits but I do not doubt that they will be there. I know it is heresy to run a bypass without running extended oil drains but I think it makes perfect sense. I pay $20.57 annually to own/operate the bypass and decrease wear. I also have my oil analyzed every oil change and the results are great.
(Feel free to plug in your own numbers.)
To view the spread sheet you have to use Microsoft Internet Explorer.... sorry.....I am a Firefox user myself and I don't like ie exclusive pages like this but I could not figure another way to put an interactive spread sheet here.
If you cannot view the interactive spread sheet click here for a non-interactive version.