Are you saying dirty oil is slow oil?

 

If you use a quality synthetic oil, you can safely use a 10K mile OCI (After the OEM fill (dino oil) has been changed).

Koz

 

Your oil is dirty with byproducts of combustion after 100 miles. That doesn't mean it's prudent to change it after 100 miles.

Folks, OCI is a balancing act. No engine will run forever. Eventually it will wear to a point where it needs to be rebuilt. OCI is based on service life and repair cost. You'll spend a certain amount of money on maintaining the engine vs. a certain amount of money rebuilding the engine. From a dollars and cents perspective, if your oil retains its ability to perform the basic functions it is there to do, then it is too early to change it. As its ability degrades (and it does from the first mile you put on it) you play a balancing game. How far can I take it without significantly affecting the engine's service life.

If your idea of service life is 100k miles, you could probably get away with oil changes every 15k unless you drive very short distances all the time. If you expect 200k service life, you'll probably want to cut that down to 10k. If you are going for the million mile engine, then you'd better plan on following the manufacturer's recommendations.

You're going to spend a LOT more money for oil with the million mile plan ($6000 @$30 per change - more if you specify synthetic). Keep in mind, very few of us will keep a car past 100k miles. Using a 10k OCI cuts the oil cost in half. Also, if you are like me, your time is worth money. More trips to the shop to get the oil changed is more lost opportunities to make money. My time gets billed at ~$250 an hour, and I waste at least an hour and a half dealing with an oil change done my someone else. Again, another cost/benefit trade off.

Finally, no matter what oil you choose there will be seals and hoses on the engine that will need to be replaced well before the magic million miles, and often even under the best conditions the rings will wear to a point they do not seal well - especially with forced induction - so it's entirely a balancing act.

With all due respect to the guys at BITOG, the truth about industrial engines is they change oil when the accountant says it makes sense. Not when the wear metals "look" bad, but when the cost of continuing to run the oil outweighs the cost of taking the unit off line for rebuilding. I have a friend who has been doing power production with large engines for many years. He laughs at all the arguments about oil people on the Internet have. When you are changing hundreds of gallons of oil on a 1000 hp generator engine, and you know the engine will only last a certain number of hours at a given load before another rebuild, you really need to think about cost/benefit because it directly affects cost/kW-hour. The accounting guys are always looking for a way to reduce that number.

 

This is what I'm thinking... tell me if this is correct...

It's not that people intend to keep their cars 150K, 300K, or 1M miles. It's the thought that a engine that can last 300K will be less likely to break down at 50K compared to the engine that will last 150K.

How much less likely, I don't know. But I think that's really the argument being presented by those who recommend more maintenance vs less. So even though Technique will be out of his car by 50K, the last 10K of those miles could be much more troublesome than the same car but better maintained for the long haul?

 

You could probably run 50k on the original fill and not have a failure. There are people who have done this.

I don't believe the likelihood of an oil related failure increases much from 0 - 50k pretty much regardless of your maintenance schedule. It's when you get to 62k miles (100k km) that you start seeing serious problems (like ring sealing or valve stem seal failure) because the iron content of the oil makes it abrasive enough to cause highly accelerated wear rates.

 

I have read several posts through the years that indicate most engines will fail at approx 40K miles, if the OEM fill is not changed.

There is no need to guess how long you can safely go between changes. Just send samples to have analyzed at different interval, to see exactly what a safe OCI is.

Koz

 

I'm just wondering how often people change their oil on their cars. (Eather by mileage or so many months) for the people who don't drive a lot like me. How long do u go before you change the oil. I think my cars is 7 or 8 months old and only has 1,800 miles. For me to hit 5k might take me 2 yeas. Any info would be nice.

 

i will still go by the mileage. The oil shouldn't turn bad because of time.

 

THe ISX50's have an oil sensor that lets you know when the oil needs to be changed. These engines are efficient enough for 5k intervals with non-abusive driving. I did my first oil change at a little over 1k to remove the new engine debris during the intial break-in period.

 

Oil itself doesn't go bad with time but the detergents/additives do. This may lead to gunk buildup (the dreaded "gelling"?) if oil isn't circulating regularly. Moreover, if you only drive short distances, the byproducts of incomplete combustion (primarily carbon) can build up and make the oil dirtier than if you drive longer distances and let the engine warm up fully ("severe service conditions").

Most service interval indicator systems are based on the amount of gasoline consumed (as opposed to time or miles). Someone who drives hard/fast will use more gas and therefore the service indicator will come on earlier (but not early enough for your purposes).

I would change the oil every 6 months with your current mileage.

 

That was well said and a proper prescription. My props to you. Yes, most are based on fuel consumption. Some vehicles like the Cadilac STS are based on an integrated oil sensor. Amazingly, the system compensates for the better longevity of the standard synthetic Mobil 1 oil. These systems typically do not account for a vehicle sitting in storage where the oil life can easily become shortened.

 

Use a good synthetic and change it once a year!

Koz

 

The oil change warning on the IS is not an oil sensor, nor is it based on fuel consumption. It is based strictly on mileage. The system calls for an oil change 5,000 miles after being reset (and warns 500 miles prior to that) regardless of whether you're putting on easy highway miles, doing taxi duty in the city, or spending all day drag racing.

If you search the archives, you'll find a thread where people have posted their used oil analysis reports. UOAs are inexpensive way to confirm that the oil change interval you're using is appropriate for your specific engine and driving conditions.

 

Regardless, I would never take it to 5k interval, 4k max. I will be switching to synthetic shortly after my comped 15k service. I think there is more to the "IS" system than mileage, my system required a oil change at 4200 miles from the last because my driving conditions warrented it.

 

Well, this is certainly how my Prius works. I haven't had the IS250 long enough to figure out what they put in there but I'm guessing there's a family trend!