[Drivingforfun]

Another silly curious question

I read increasingly smaller intervals of people recommending ignoring manufacturer oil change mileage and changing more often; every 10,000, 6,000, 4,500 miles etc… just read someone today who claims to change every 1,500

Assuming time and resource waste is not an issue, what would be the optimum interval…? Is more frequent always better or is there a point where it’d do more harm than good, like changing the oil after every trip?

No reason for asking, though I’m aware some race cars probably go tens of miles between services so perhaps a slightly relevant question

[Mark07]

I don't know about the most optimum interval, but for the average (non-high performance) driver, I'd be amazed if there was a tangible benefit having an oil change beyond the annual service.

[TC1474]

@Drivingforfun I used to do a lot or work with Total and so I got the opportunity to learn a lot about how modern oils work in comparison to the oil produced say 50 years ago.

Anyway, what surprised me talking to the boffins was that modern oils don't break down like they used to, and these days oil will do the same job at 500,000 miles as it did at 50 miles.

However, it is the filter that needs to be changed, and obviously levels need to be kept right to avoid overheating and the physical burning of the oil which causes the deposits to form which create the blockages and debris in the filter.

I have also heard a similar account at Castrol who I have also worked closely with in the past, so it wasn't just a one off, and in fact an old friend of mine used to road test engines over many thousands of miles without an oil change to prove the point and there was no difference in how the engine wore.

The manufacturers usually give recommended oil change intervals because that is how they make their money, but the reality is that changing often is not a requirement and I was told that in some cases changing too regularly can actually cause damage.

[olduser]

I would expect a slightly used filter would be a better filter than a brand new one.

It is difficult to know when an oil filter is blocked because there is a filter bypass system to keep the oil moving should the filter be blocked or frozen.

I read somewhere, the American Army ran a group of vehicles without any service at all, compared to a similar group with full manufacturers service, comparing their life time usage and cost.
The un-serviced vehicles came out miles ahead, literally, and had a longer life at lower cost.
But what they call a long life may be much shorter than cars are run.

[Rolebama]

Oil contamination is linked to usage. Short journeys with cold engine will contaminate oil faster then long runs with a hot engine. The oil itself will still be fine regardless, but will pick up contaminants. Unburnt fuel, carbon and a smidgeon of swarf, even in relatively tiny amounts will render the oil next to useless. I used to have a friend at Shell who would check oil in the event of engine warranty claims. More often than not he would declare the oil good for another 20,000 miles or more if it wasn't for contaminants. He would occasionally stick his neck out and say that the oil filter has passed it's due date, allowing unfiltered oil to circulate, most commonly causing shell bearing failure. When I worked at a garage dealing with Vege engines, we would receive similar reports denying warranty claims.
The point is that changing the filter is more important than changing the oil.
FWIW I change my filters at around 7/8,000 miles, and oil at 15,000 or annually.