Very good post Justin!

 

here is something to think about.
I have friend who owned a 05 diesel, he put 400,000kms on it it was used 8-10hrs a day every day, it was used for intown courior work, He changed the oil without fail every month as he put on 5000kms(3000miles), at 400,000 kms the engine failed (broke the rings in one cyl) now I doubt this was an oil related fail, more likely a mechanical failure, he paid approx 100$ per oil change as he did not do them himself

so 400,000kms divided by 5000kms = the number of oil changes done which is 80.
80(oil changed) X 100$ (cost of oil change)= 8000$ thats alot of money to "protect" an engine which failed not due to an oil related issue.

so spending 8000$ on oil changes seem poorly spent if you ask me as that 8000$ could buy a new engine, which is better a running 400,000 km engine or a truck with 400,000on the odometer but a new engine under the hood?


so to compare:

my truck was used for the same work but I did extended drain with oil samples taken to help decide what is the proper interval (oil samples cost approx 20$)

my oil change with amsoil is approx 110$ and I change it every 30,000kms
at 6months I log 30,000kms and 1000hrs of engine run time

so same math

400,000kms divided by 30,000kms = 13 oil changes
that means I spent 1460$ for my oil changes so I saved approx 6530$


Amsoil says their oil is good for 85,000kms or 650hrs or 1yr which ever comes first WITHOUT having it sampled, all the above being said I could have extended my changes even further as the samples kept comming back saying oil was still good for continued use!.

I used my truck for my income, so oil changes are a tax/business write off, you would think it would be in my best intrest to do more oil changes...but its not.

My truck is now used for personal use as I dont courior any more so I've reduced my oil changes to once a yr, and I ignor the mileage because I'll never even get close to the recommended change interval (but I still sample it just the same)

I did not buy my truck new as my friend did, mine had 297,000kms on it when I started using it for courior work, it now has 520,000kms on it, so the moral of the story is its a personal choice which is better to use, and this is an arguement that will never ever be decided, only advice I have is wether its syn or dino oil have it sampled and base your oil interval from that.

 

Another great point nickg. Not to get off topic but I have said the same thing about how much money guys dump in their fuel tanks investing in fuel additives trying to save their injection pump. Its crazy. Spending double, triple, or quadruple the amount of somethings replacement doesn't really seem like the right thing to do but no matter, its all up to whomever owns the truck and what they feel better doing. I'm not here to chastise anyone for using synthetic.....just the guys who still think that they need to change their oil every 3000 miles.

 

Even in an absolutely terrible duty cycle, you're throwing away perfectly fine oil at 3000 mile ODIs with almost any oil.

Even if you're getting 10mpg with wicked heavy hauling, that's still a 6K mile ODI using my 200gal/gal rule.

Sort of related to this:

Why are the recommended intervals for the Dodge application so short? My '02 came with a 7500 std/3750 "severe" oil drain interval from Dodge.

Let's say you do all hwy miles and won't follow the "severe" schedule. 7500 miles on 3 gallons sump capacity is 2500 miles per gallon of sump capacity. Most of us can get about 20 on the hwy.

This means Mopar is taking my "200gal/gal" rule of thumb and making it 125 gal/gal.

Now let's apply that same reasoning to an ISX getting 6mpg and see what ODI you get. 125gallons of fuel*11gallons sump capacity*6mpg= 8250 miles!

There's not a trucker on the planet that would change the oil on a big rig at 8250 miles! The cost of oil changes would put him our of business.


Yet, this is the very LONGEST that Mopar would have us go on a factory CTD of a year like mine? Since almost anything qualifies as "severe" according to Dodge, I should be changing my oil every 3750 miles.

Yet, normalizing for MPG and oil capacity, this would have me changins ISX oil every 4125 miles.

I don't think there exists a duty cycle bad enough to need to change an ISX's 11 gallons after only 4125 miles.

The Mopar recommendations seem a little ridiculous.

They make a lot more sense to me when the changed them for the HPCR to 7500 severe/15000 normal.


JMO