Originally Posted By: TiredTrucker
There are differences, for sure, Festiva, but AP9 left the comment wide open. He said there is no way 25,000 mile OCI's are any kind of good irregardless of engine, oil, sump size, anything. So, my comment was indeed valid. He set the standard for the debate, I commented accordingly.
Sure, one can always come up with anecdotal examples of long OCI's someone is doing. That wasn't the point. I was stating that those OEM's themselves are recommending over 25,000 mile OCI's as a counter to AP9's argument. And they recommend those intervals on regular, off the shelf conventional oil, no bypass, none of the other stuff you mention either. Just simple drain and fill intervals with stock full flow filter. And many of those running over 25,000 mile OCI's are not using much more than about 2-3 quarts of oil in that time frame. And that on 13-15L engines. So make up oil isn't changing the dynamics much on 10 gallon sumps. That is equivalent to having to add 1/2 quart to a auto in 25,000 miles.
Either way, it is all just fascinating anyway. I only go to just under 10% left on the OLM on my pickup irregardless of the oil or filter. I have no interest at all in trying to establish some new OCI record. It is only 6 qts and a filter. Even if I was using Amsoil and their 25,000 mile claim. I just never felt the need to take them, or anyone else, up on it. Not sure why anyone else would either except just out of curiosity. My curiosity has never been that piqued.
i know what you said is right, i just didnt want anyone else thinking they could do that in a car...
yes, even oem oci reccomendations for light duty diesels like f-350's are a fair bit longer than a passenger car, i just made that point to show that people can and have gone much much farther than reccomended on regular oil. just that i think you do need to top up in that time to do that. on a large diesel when they calculate how long they want to reccomend for an oci they wouldnt take any oil burning into account right? i think the 25k mile oci reccomendation on large diesels is the same as the 3 or5k oci's light cars have or used to have. safe for any reasonable application and you could probably go longer.
my curiosity was piqued when i found out honda reccomends 16,000km oci's with 32,000km filter change intervals on conventional oil. i thought there was no way you could do that if you wanted your engine to last longer than the warrenty. now im getting oil analysis and trying to see how far it can go
Originally Posted By: AP9
Yes I did paint with a broad brush there; however, for automotive internal combustion engines, I stand by my statement. Diesels for class 4-8 trucks are a whole different animal as they have vastly larger oil sumps (50+ qts in some cases), and I think everyone should be on board with the concept that more oil capacity translates to longer usable life, yes? But how many car or light truck engines can you name with sumps greater than about 8 quarts? A lot of things can happen over the course of 25,000 miles, and the majority of us are not just cruising along at constant low-load RPM for that full 25K.
Synthetic vs. conventional is almost a moot point nowadays, considering current Noack volatility and shear stability requirements outlined in API SN.
thanks for clarifying, but still, if your doing 25,000 miles (40,200km) in a year it has to be mostly highway driving. if you tow, race, drive in cold weather, mountainous areas or dusty areas you are in severe service which amsoil reccomends 15k for i believe.
so to qualify for their 25k you cant put any decent load on your motor, do any cold starts with it or drive where its dusty. and it has to be mostly highway miles. so most of the bad stuff in your 'a lot can happen in 25k' is irrelivant i think.
i would disagree with your synthetic vs. conventional statement. conventional is good enough for 99% of cars or big rigs on the road. i have 425k on my car engine that has been beaten on hard, raced, overheated, started in very cold winters down to -42c, seen a lot of gravel roads, towed and hauled heavy stuff and revvs at 3k rpm at highway speeds which is mostly what i drive with it. all on conventional oil. didnt burn a drop until last winter and i think that was because all the porcelin came off a spark plug and fell into the cylinder and scored it up. anyway, synthetic has better properties for more than just volitility and shear. if you drive a lot and dont want to change your oil every 3 weeks its the way to go. if all you do is race or tow close to your max weight rating and dont want to change oil every few times its the way to go. other than that if your going to change your engine oil at the manufacturers reccomendations there is really no reason to use synthetic that i can see. all the oil has to pass the same test so its good. but the kid that got 100% in math will probably make a better math teacher than the kid that got 51% even though they both passed. but if all you want is a secratary either one will do just fine.
