OCI, not when but why?

PunchT37 · 2026-08-03T21:38:38Z

22 minutes ago, Chuck FB said:

I don't know how far back vehicles had hour meters, be it driver accessible or diag accessible but was wondering if there was any rule of thumb your shop came up with in regards to an hour limit on engine oil regardless of the miles on the oil.

I know with construction or farm equipment its almost always based on engine hours for maintenance scheduling as no other metric really applies other than a seasonal time limit that one self imposes on items like engine oil.

When I was there, most to all did not have an hour meter. They just did 5000 miles on regular vehicles and 3000 on police stuff. The modern oil change monitors should take into account engine hours, weather, etc. I don`t use the monitor on my stuff. I pull the stick, look at it, smell it, rub it between my fingers, etc. That`s my oci.

I have had many engines. Some bracket race. No problems doing things my way. I was in the mechanic business for 30 yrs or so. I still do things the old school way. Don`t care who laughs at me.

Understand, I was in the main shop. We didn`t do oil changes or tires. We had a service station for that. I don`t remember the hours they used for tractors, lawn mowers, etc. Something in my head says 250 hours.

Edited 13 hours ago by PunchT37

KARNUT · 2026-08-03T22:18:08Z

36 minutes ago, PunchT37 said:

When I was there, most to all did not have an hour meter. They just did 5000 miles on regular vehicles and 3000 on police stuff. The modern oil change monitors should take into account engine hours, weather, etc. I don`t use the monitor on my stuff. I pull the stick, look at it, smell it, rub it between my fingers, etc. That`s my oci.

I have had many engines. Some bracket race. No problems doing things my way. I was in the mechanic business for 30 yrs or so. I still do things the old school way. Don`t care who laughs at me.

Understand, I was in the main shop. We didn`t do oil changes or tires. We had a service station for that. I don`t remember the hours they used for tractors, lawn mowers, etc. Something in my head says 250 hours.

We did 250 on our tractors until we switched to Amsoil. We doubled after that.

Grumpy Bear · 2026-08-04T01:45:12Z

5 hours ago, PunchT37 said:

I agree. That`s a LOT of sludge for 12,000 miles. I tossed that out here since this is an OCI thread. There`s tons of people here that do not post.

I used to work on a city fleet. That includes police cars and fire trucks. Lesson is, not to only use the odo for oci. A police car has a ton of hours on the engine for the miles it shows. And, not just idling, directing traffic. They beat on these things.

Course, since it is a Kia, they were gonna use the "100,000 mile warranty" for their OCI.

I knew a guy in the early 80's that bought a new Monte Carlo and ran it a 100,000 miles without ever changing the filter or the oil. Just kept adding. It looked like that inside.

Grumpy Bear · 2026-08-04T02:01:11Z

11 hours ago, diyer2 said:

I did shorter OCI"s for many years without an issue, fights sludge and wear IMO. Recently started using Amsoil, will not do the recommended/advertised miles between changes.

In the 80's 90's I'd run Honda's 7,500 miles between changes using Red Line HP 5W20 and do it for hundreds of thousands of miles with issues. Back in the day it was an SAE 20 with the HTHS of a SAE 30 and SN add load. It was also very polar. Oxidation VOA was over 120. Besides those motors were SPFI and lean burn tech. I could have likely run it longer but never did.

We had a Toyota bought new I ran on Pennzoil's latest and greatest synthetic of the day with "Penthane". A made up word for a very low dose of PAO. Tried 7,500 mile OCI's in that Group III/VI chemistry and the rings tapped out at 90K. Rocker box wasn't as bad as the one Punch put up but it wasn't good either. Also a SPFI motor.

I'm around 3,750 across the board on these GDI monsters and the oil it tapped out by then usually on TBN/TAN crossover and color. Red Line HP Euro.

The AMSOIL SS brochures tell you to follow the OEM values for the service class but that it can be run up to 25K if monitored. I can't imagine what motor could go that distance and not tap out. I've never owned one.

Yes, I know. Lot's of people do. I'm just not going to be one of them.

Chuck FB · 2026-08-04T02:24:56Z

34 minutes ago, Grumpy Bear said:

I knew a guy in the early 80's that bought a new Monte Carlo and ran it a 100,000 miles without ever changing the filter or the oil. Just kept adding. It looked like that inside.

I am guessing that engines of that design back then had a better ability to be abused and survive longer than a new design engine with the long timing chain and the overhead cams and phasers etc. But I would never guess that an engine could go that far and not fail spectacularly or at least die a slow death.

Chuck FB · 2026-08-04T03:33:03Z

1 hour ago, Grumpy Bear said:

In the 80's 90's I'd run Honda's 7,500 miles between changes using Red Line HP 5W20 and do it for hundreds of thousands of miles with issues. Back in the day it was an SAE 20 with the HTHS of a SAE 30 and SN add load. It was also very polar. Oxidation VOA was over 120. Besides those motors were SPFI and lean burn tech. I could have likely run it longer but never did.

We had a Toyota bought new I ran on Pennzoil's latest and greatest synthetic of the day with "Penthane". A made up word for a very low dose of PAO. Tried 7,500 mile OCI's in that Group III/VI chemistry and the rings tapped out at 90K. Rocker box wasn't as bad as the one Punch put up but it wasn't good either. Also a SPFI motor.

I'm around 3,750 across the board on these GDI monsters and the oil it tapped out by then usually on TBN/TAN crossover and color. Red Line HP Euro.

The AMSOIL SS brochures tell you to follow the OEM values for the service class but that it can be run up to 25K if monitored. I can't imagine what motor could go that distance and not tap out. I've never owned one.

Yes, I know. Lot's of people do. I'm just not going to be one of them.

Its no wonder you've gravitated to the oil types and brands you have in later years after trying certain brands and one being a specialty oil or at least very hard to come by up here and the other would have been a commonly found oil of the era and the vastly different outcomes as a result to using the vehicles in question the same distance for an OCI . It shows what marketing hype can do without actually having the product to back up the claims and that is no different now with the insane claims that are written on the side of a bottle of oil from some of the off the shelf oils.

What has surprised me and I was already finding this out before I bought my truck with the GDI engine, that this newer fancy technology that seemingly would suggest better fuel economy/emissions with this high pressure spray of fuel is not in reality kind at all to the engine or at least the oils life. Yet they insist on claiming long OCI with this technology just like they did with the port or similar type fuel injection systems when in reality its a step back in oil life to have a GDI system.

I think the mistake your making Grumpy is that your not sending your samples to Blackstone and getting the feel good glowing report that you can run it another 1000 or more miles and then send another sample where they say run it yet another 1000 miles and on and on it goes until your sending in something that looks a lot like road tar and then they may suggest you change your oil within the next 1000 miles