Now I know this has been covered a lot, but no one could ever really answer the question I have. Figured I'd ask here since we have our own oil expert on board. I know the change interval in the manual says 7500mi. My situation in a bit different being my truck only sees ~ 5000 mi. a year. It is a work truck and I usually only use it to pull trailers and haul. It does not see a lot of highway driving either. I use Rotella 15-w40 and change twice a year or every 2500 mi. Can I change only 1 time a year and be safe? Should I go to synthetic if I only change once a year? Our mech at work is old school and still believes in the 3 month 3000 mi. thing. Some of the vans there may only have a few hundred miles on but still get changed every 3 month. I believe that is over kill as oil has improved a lot over the years but I don't know. Is 1 year too long? 6 months too long? What would you do?

So this might be stupid on my part but after doing head gasket I still haven't changed my oil, put almost thousand miles on it since. I now have 3500ml on the oil. I don't believe water ever got in oil and I do have a bypass filter. So I'll be changing it this fall when I get around 5k on oil. It is still half clean on dipstick, I do know if I put it in a bucket it will look black. Smells ok too. Screwed up part is I got 20 gal of new oil and like 8 filters, I guess I'm wired like that. 

20 gal lol.

i have over 100 of travellers 15/40 and over 60 valvoline 15/40. and around 30 valvoline 5/40.

and roughly 35-38 of 5/30 supertech for my wifes car. i stocked up on the older CJ-4+ stuff when i had a chance. now i mix it about 50/50 with the newer CK stuff.

Why.. cuz i'm an odd one.

and as i said before, i change my oil's once a year. roughly 8-9K miles.

my next investment is a oil burner stove/furnace to heat the garage.

14 hours ago, dave110 said:

They make a little digital 12vhour meter for lawn & garden equipment that only costs like $25. I often thought of wiring one up in the truck but never got around to it.

But my question is TIME. 15 k miles takes me 3 years to accumulate. IDK, seems too long.

I may just do this. Do they give a recommendation on time too, or just mileage?

Just based on the number of miles on the current sample. I have every change tested, but only basic test which is $28.

13 hours ago, Killer223 said:

now i mix it about 50/50 with the newer CK stuff.

Probably not a good idea, but I've done it myself on other vehicles 

Why is it not a good idea? the CK is "backwards" compatible... so the way i see it i'm adding some of the good ol oil to the newer not so good oil, in order to make a half way decent oil.

this is the oil i run

https://www.tractorsupply.com/tsc/product/traveller-premium-all-fleet-15w-40-diesel-engine-oil-1-gal

 

no issues. we ran this in the tractors onthe ranch for years n years. the old massy still going strong.

 

I run that in my skid steer as well. I should probably just use it in the truck too, but I like that Rotella smell.