The longest I've gone before changing my oil was nearly 8k miles. But I try to stick to around 6-7k miles.

Based on the TBN I got in my first oil analysis, I would expect the Subaru branded 0W20 to reliably go about 11K to 12K. However, I'm still changing mine on 7500 mile intervals to stay well within the safety margins and to keep there from being any warranty questions when my engine blows up again.

You can actually increase wear by changing your oil too often. New oil has a period in which the volatiles are being burned out of it. The breakdown of the volatiles results in sludge and deposits. Then you hit a sweet spot of several thousand miles in which the volatiles have stabilized and the detergents in the additive package do their thing of cleaning up any deposits left behind.

If you change your oil too often, the only part of the cycle you get is where crap is being deposited into your motor. Back in the 70s you didn't have much choice because the additive package would run out after 3K to 5K miles. However, now that the detergents have gotten so good, the sweet spot is considerably longer.

That's one thing that makes the UOA so handy. With a TBN added to your analysis, you can see how well your oil is doing, and it provides a lot of comfort around the longer oil change intervals. I usually only get a TBN if I'm using a new oil I haven't used before.

As was noted above, the basic test is $28, but you also have to consider shipping cost. I sent my first sample via USPS in the provided mailer bottle, and the idiots at the local post office stuck it on a shelf for a month because they didn't know what to do with it and didn't actually send it until I got my local postmaster involved. Now I put the whole mailer bottle inside a padded envelope and send it UPS. It costs more, but at least I know it will get there.

Additionally, the way most people take their sample is to hold the collection bottle in the oil stream as the oil is being drained. Obviously you can't do that if you have your oil changed at the dealership. You can get a service tech to collect your sample for you, but you can't be sure they'll get it right and not contaminate it. I solved that problem by purchasing the $35 vacuum pump from Blackstone so I can pull the sample through the dipstick tube before taking the vehicle in for service.

The UOA can help you decide whether you need to do that. Blackstone actually commented on how well the Subaru filters on the BRZ are working at 7500 mile intervals.

That's a totally new one on me. As a lifelong "trust but verify" guy, I'm going to bounce that off a couple local guys who know a WHOLE lot more than I do and will report back. I find it hard to believe that fresh oil is somehow more damaging to your engine than oil that has been utilized for several thousand miles, but hey, I'm open to being edumacated.

Thanks for the response.

Barry

above is my exact situation as well.

it piques my interest reading all the oil analysis reporting okay beyond 10k, i just havent taken that gamble yet.

Some of the diesel truck drivers are running Rotella synthetic 25K or 30K miles without losing any effectiveness in the lubrication (at least according to their UOAs). As long as you have good filtration, modern motor oil can last a pretty long time. Once upon a time the filters were not as good, the oil was not as good and the detergent was not as good, so the volatiles were the least of your worries. Now that conventional wisdom has been upended.

So Cal and 626? The yolo is real for the 626 guys. LOL /s

That's what I've been doing, every 6 months**. But then my research shows me that changing too frequently can be bad bc of the breakin period...

wut?

Switch to Amsoil and you could go to 25k or more on an oil change. The stuff is amazing.


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25k? Got any proof on that?

Why not just stick to 5k intervals? Imo stretching it out is penny wisdom/pound foolishness.

Because even the factory says 7500 is ok. My car is mostly stock so I'll adhere to that schedule.

When the motor has consumed a quart, change it. I keep the level topped off but when the bottle is empty, I change the oil soon after. Consumption increases with rpms, as it should.

Because there is factual evidence you don't need to.

Modern engines, and the fluids that go in them have come a long way. Go look at the oil change intervals on a modern Lamborghini, they use off the shelf oil from Castrol.

They recommend oil changes at up to 10-20K miles, thats more than most lambo owners will ever put on their cars.

Its not about penny pinching, but why change your oil 2-3-4kmi's early if you dont need to?

All I know is that I feel way more scrape / wobble / slap on cold start (30-40*) with old (4000) mile oil more than I do on fresh oil. On ignition you can feel the friction. That's enough evidence for me. I say change it before 5000 miles.