OCI base on time

[lockguy]

What is it with oci recommendations base on time. For instance, 3k or 3 months for conventional oil? Maybe its 6 months now, i don't know.

does oil actually get old sitting in the engine? oxidation in the engine uses up the add pack? If a good solid conventional oil is good for 5K, why not keep it in for 5k regardless(within reason) how long it takes, 6 months or 1 1/2 yrs...does it matter?

 

[Chris142]

The oil in my truck was as good as new after 3 years. Eventually it will need to be replaced but not 3 months. Like the old days.

 

[Kuato]

+1 There's been a couple of threads on this lately, and as long as you are not taking lots and lots of short trips the oil should be fine. If you're concerned then an UOA will tell if your driving habits are using up the additives or not.

 

[ChrisD46]

Below for suburban , mix of short / medium trips , stop & go daily driver :

Dino 4,000 miles / 4 months
Synthetic : 6,000 miles / 6 months

What I suggest above leans more towards the easy to remember OCI's - but with big city driving (ATL) the OCI's above work well for being close to when the oil needs to be changed .

 

[miniac007]

Depend on the oil you use:

- I used Q8 T1000D and after one year, the TBN fell down, and it is time to change oil. Two years, it was to late...

- I used Total Rubia TIR 8600, and the TBN was very strong after 4 years...

So use UOA to monitor oil TBN/TAN over years and choose the oil aging best...

 

[bigt61]

A buddy of mine just came by driving his old '89 Lincoln Mk 7 (5.0L V8) which he doesn't drive much. I asked him when was the last time he changed the oil? He said 11 years ago just after he bought it! He used M1 10w30. As best as he can remember he's gone about 10,000 miles and added a quart or 2 of make up oil during the 11 years. The dipstick showed full, had no varnish and the oil didn't even look that dark. The motor sounded quiet and smooth. He's going to change the oil soon. He routinely goes 15-20,000 miles on his DD - a 95 Chrysler mini van with 290k miles - he uses SuperTech Synthetic in that and adds 2-3 qt during his OCI.

 

[Quattro Pete]

Originally Posted By: lockguy
If a good solid conventional oil is good for 5K, why not keep it in for 5k regardless(within reason) how long it takes, 6 months or 1 1/2 yrs...does it matter?

I think it really depends on how the vehicle is driven. If it's only longer but infrequent trips, I'd say no problem. But if it means mainly very short trips where the oil can't stay at operating temp long enough to burn off moisture and fuel, then such long OCI in terms of time may not be too good, regardless if it's conventional or synthetic oil.

Take a look at my two PU 5w-40 UOAs in this thread: One was 6K miles and 16 months (2 winters), the other one was 5.3K miles and 12 months (1 winter). Looking at TBN/TAN, the 16-month one took quite a bit more beating, to the point where the lab flagged it as "abnormal".

https://bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=2983142#Post2983142

That longer OCI one had more short trips on it.