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2005 Forester Automatic
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Discussion Starter · #1 ·
OK, I am getting more and more in love with the 10k mile OCI that my Prius recommends. Plus used oil and filters are a bad thing for the environment. And they cost.....

So I have been reading about extending the OCI with synthetic oils in my 05' Foz. Factory OCI is 3k miles, but that is with original spec'd oil that was far poorer quality. I also tend to add a quart every 2k miles due to some modest oil consumption.

I am using Mobil 1 High Mileage 5w30 Synthetic. So if I pushed the OCI to 6k miles, I would actually be dropping about 2 quarts of fresh oil in (at 2k and 4k miles). I'd probably never get even to 6k miles, as I still would like to change the oil 2x yearly (Spring and Fall), and I don't put 12k miles on my Foz anymore.....

I doubt there is any "factual" data, and I recognize that I am going to get opinions here. So what's your opinion and how do you support that opinion?
 

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2019 Crosstrek 2018 Forester XT
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Just go with a good dino oil like Pennzoil yellow bottle and since you are using that much oil (which is not great for the environment) you can easily go 10K miles. The EJ is very easy on oil.

Optionally you could go with at least 2 bottles of 5W40 with the 30 wt.

Just to prove it to yourself do an oil analysis at7500 miles..you'll see.

Dino oils are not your father's diono oils. They have great additives. They resist thermal breakdown almost as well as synns.
 

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1999 A/T - 235,000 mi. WA state
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Well Herman, you're really on top of this - and I mean it favorably. Do what you decide and let us know in a year and 2 how it's working.


I use my car mostly in the winter, for bad weather short trips, and I change oil frequently. The cost of the oil changes is minor in my opinion.
 

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'17 Impreza Hatchback CVT
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Of course, your Prius engine isn't running 100% of the time either!

Just pointing that out for fairness - my other car is a Gen II Prius :grin2:

Personally, I find the 6mo/6K interval required to maintain the warranty on my 2017 Impreza is just crazy given that the synthetic oil that is required is one of the more highly engineered high tech fluids out there! :frown2:
 

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2017 Forrester
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10k OCI are a bad idea. Especially if you are using 0-20w oil, as the newer Subaru’s do. I know that evryone wants to extend out the intervals, but I really think it is a bad idea. If you are using a heavier oil, i think that it is less risky, but i still would not recommend it. 0-20w oil is a problem. If you read a lot about it, you will find that problems are beginning to show up. I too had a Prius. I was talking to the service manager at my local dealer about oul changes. He said Toyota has talked about problems with 0-20w oil and especially with 10k OCI. He said he is seeing more Toyota problems in engines with 70 to 100k miles than ever before and in talks with Toyota they are seeing it too. Whether it is due primarily to the 0-20w oil or to 10k OCI, is debatable but i think it is a combination of the two. As far as I know, the US and Canada are the only countries that use 0-20w oil. Subaru’s, Honda’s and Toyota’s in the motherland (Japan) use 5-30w oil. The US and Canada pressure the auto makers to use 0-20w oil and give them rewards for doing so. 0-20w does improve mileage a little, and with that being the Fed’s buzzword, it is pushed quite hard.

I use 6k OCI on my Forester, even using fully synthetic oil. I use 5k OCI on my Audi, even using a top brand fully synthetic oil. I know what you read from the oil companies about extended oil intervals, I see the ads too. But i find a lot of information and a lot of experts that disagree. I suppose you could tell me it is just people that want you to buy more oil, but I don’t think so.
 

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Extending oil change interval on older engines with synthetic oil?

0-20w does improve mileage a little

Is there any reputable source that backs that up ?
Id really love to know if thats fact and if so how much or little.
My guess is its minuscule and the risk isnt worth the gain.
Would be a good episode for Myth Busters. Lol



Sent from my iPhone using Tapatalk
 

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2019 Crosstrek 2018 Forester XT
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10k OCI are a bad idea. Especially if you are using 0-20w oil, as the newer Subaru’s do. I know that evryone wants to extend out the intervals, but I really think it is a bad idea. If you are using a heavier oil, i think that it is less risky, but i still would not recommend it. 0-20w oil is a problem. If you read a lot about it, you will find that problems are beginning to show up.
There is no earthly reason why a quality oil will not hold up in a 10,000 miles in a mechanically sound engine. I have reviewed many hundreds of 10,000 Used Oil Analysis.. Wear metals are fine and so is the oil viscosity and additives. I have performed 3 10K mile oil drains on 2 different 2008 Foresters and did UOA's on both. They were fine even on a Supertech Syn. And the OP's vehicle uses a quart every 2000 miles so if he ran 10 miles that is jlike running 10K miles. Its just not a problem. BTW the one subaru now has 193K miles and is in great shape. The other was wrecked at 145K miles.

Is there any reputable source that backs that up ?
Id really love to know if thats fact and if so how much or little.
My guess is its minuscule and the risk isnt worth the gain.
Would be a good episode for Myth Busters. Lol
I am currently running my 2018 XT on 20 wt. I will just be doing it for cool weather and will only do it for a couple weeks. I have done 9 10 mile trips all under similar conditions Oil temp, speed, and terrain. Mileage averages 35.2 mpg. Of course I don't use boost and won't with the 20 wt. 30 wt averaged 32.3 mpg. So its north of 6% improvement. The FA engine was designed for 20 wt and a Compression ratio of 12.5 the boosted version is only 10.6. and calles for 30 wt. oil. So running with no boost, in cooler weather. No reason to worry. And it will be short term. I did it out of curiosity. :)
 

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2017 Forrester
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There is no earthly reason why a quality oil will not hold up in a 10,000 miles in a mechanically sound engine. I have reviewed many hundreds of 10,000 Used Oil Analysis.. Wear metals are fine and so is the oil viscosity and additives. I have performed 3 10K mile oil drains on 2 different 2008 Foresters and did UOA's on both. They were fine even on a Supertech Syn. And the OP's vehicle uses a quart every 2000 miles so if he ran 10 miles that is jlike running 10K miles. Its just not a problem. BTW the one subaru now has 193K miles and is in great shape. The other was wrecked at 145K miles.



I am currently running my 2018 XT on 20 wt. I will just be doing it for cool weather and will only do it for a couple weeks. I have done 9 10 mile trips all under similar conditions Oil temp, speed, and terrain. Mileage averages 35.2 mpg. Of course I don't use boost and won't with the 20 wt. 30 wt averaged 32.3 mpg. So its north of 6% improvement. The FA engine was designed for 20 wt and a Compression ratio of 12.5 the boosted version is only 10.6. and calles for 30 wt. oil. So running with no boost, in cooler weather. No reason to worry. And it will be short term. I did it out of curiosity. :)

This is exactly what you get on any forum in any discussion about oil. Completely different opinions. Everyone is certain that they are right. I am not going to argue ober this other than to say that from what i have read and have seen, i would not follow a 10k OCI. Period.
 

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<snip>I am using Mobil 1 High Mileage 5w30 Synthetic. So if I pushed the OCI to 6k miles, I would actually be dropping about 2 quarts of fresh oil in (at 2k and 4k miles). I'd probably never get even to 6k miles, as I still would like to change the oil 2x yearly (Spring and Fall), and I don't put 12k miles on my Foz anymore.....
As @JDS pointed out, you will likely get conflicting opinions. Here are a few thoughts that might help you in your quest.

- Perfect a consistent way or habit of checking oil (e.g. drive in the garage, stop engine, wait 10-20 minutes, check oil). It doesn't matter so much how you do it, but be consistent. Preferably, check the oil when the engine is hot. Keep written records.

- Synthetic oils are thin by nature. Viscosity Index Improvers (VII) are added to made them thicker (say, turn 5w-10 synthetic base stock into 5w-30). If the VII wear out, the oil tends to thin back to its original nature. I like and use Mobil-1, but in my experience it suffers from this change-in-nature more than some other synthetic oils, such as Castrol Syntech.

- Mineral oil tend to be thicker by nature - VII are added to thin them down at low temperatures (say turn 20w-30 mineral oil base into 5w-30). Logically, if the VII quit working, the oil becomes thicker. That said, Castrol makes some truly excellent mineral oils which should easily hold up for a 10,000 mile OCI.

- If you think about the two paragraphs immediately above, you might decide that a blend of synthetic and mineral oil would have advantages. The one gets thinner over time, the other thicker.

- A reasonable goal of your testing might be to find an oil or oil + additive combination that will hold up for 10,000 miles with only minimal oil added (say, 1 quart or less during the whole OCI). Do that and you've accomplished something.

- If you can't reach nirvana (or even if you can), you might want to experiment with oil additives such as MoS2 or boron (Liqui-Moly has experimented with and markets both, but there are other big players in this area). From personal experience, Mobil-1 + Liqui-Moly Anti-Friction MoS2 is an entirely different beast than straight Mobil-1. The same should apply to other synthetic oils + additive, but I have less experience with them. There are also off the shelf oils that contain high amounts of these additives (e.g. Shaeffer's Supreme or Conklin Convoy).

- 10,000 mile OCI? An M54 cargo truck as used in the late 1960's through early 1970's could go 100,000+ miles on an oil change - and do that with some S.O.B. shooting at you. The oil was usually changed at the depot during a rebuild and not changed again until the truck got rebuilt again, at the depot. Think about that late at night.

I know Bimmer owners who get all teary eyed thinking about their 10,000 mile OCI. When confronted with this situation, just laugh . . . they won't know whether you're laughing with them (or at them).

---- Addendum 12/31/2018 ------

Here are a few more thoughts on an extended oil change interval:

- Consider adding an air-oil separator - particularly one which returns the separated oil to the sump. On your vehicle, you are really interested in oil that passes the rings and gets burned - not fumes in the crank case. Some cars are worse than others, but from a usage standpoint, oil that fumes in the sump simply throws off your usage numbers. An AOS is the fix.

- If you are going for a, say, 10,000 mile OCI, consider changing the oil filter at 5,000 miles. Subaru filters are rather small and, due to their location, there's no easy way to install a larger (longer) filter. Detergent oil is supposed to catch and hold in suspension carbon particles (by products of combustion). I would guess the OEM Subaru filter has enough capacity for a 10,000 mile OCI . . . but I would still change the filter at 5,000 miles to be safe. Add a cup of oil when you change the filter (to replace the oil that is lost in the change).

- Consider a by-pass filter. Industrial equipment and over-the-road trucks routinely use them. Passenger automobiles don't need them for relatively short OCIs. But just because you don't need a by-pass filter does not mean it would not be beneficial. Sadly, they are a costly add-on accessory. If the car maker included one from the factory, the added cost would be minor. With a by-pass filter and a few other tweaks, a passenger car could go 100,000 miles or longer between oil changes.
 

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Discussion Starter · #10 ·
Thanks for all the food for thought. Some of you seem to think that I was advocating a 10k OCi for my 05 NA Foz. Not in the slightest. And as for the 10k OCI for a Prius, I generally chicken out at around 7500.

What really drives this question from me, is that changing oil gets harder every year I get older. The vehicles that I drive that have the lowest maintenance needs look nicer all the time..... And avoiding environmental damage is a nice perk.... Having the stealership change the oil is an option, but the time spent would be easily 30 min more than I spend doing it personally. And having a Jiffylube equivalent do it is too much random,....

I drive a Leaf most days. No OCI. The old Foz is a dear friend, especially in bad weather. But the oil filter puked oil all down my sleeve last change and I realized how much I hated doing oil changes!!!
 

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2019 Crosstrek 2018 Forester XT
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This is exactly what you get on any forum in any discussion about oil. Completely different opinions. Everyone is certain that they are right. I am not going to argue ober this other than to say that from what i have read and have seen, i would not follow a 10k OCI. Period.
Its called discussion. If you can't deal with an opinion different from your own that's ok.
@cdherman. I understand where you are coming from.

I spent my life as a Maintenance Supervisor/Engineer in a large generating station. I have seen every lube failure known to man. And more importantly other engineers did Root Cause Analysis..so the exact cause of the failure was known. With maybe one or two exceptions (heavily loaded worm drives)I can say that in the 30 years I have never seen one failure proven bc the lubricant failed. If there is adequate lubricant the the component/engine will not fail-as a practical matter

Don't worry about oil change interval. Just keep the lubricant near the top and you are good to go. The only issue "could" be an inherent problem with the engine. That is why it may prudent to do a $30 Blackstone oil analysis.
 

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Its called discussion. If you can't deal with an opinion different from your own that's ok.
Thanks mom.

No, my point is that i see more angry, self opinionated discussions over oil than even over politics. I just don’t have any interest in getting sucked into that hole.
 

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Is there any reputable source that backs that up ?
Id really love to know if thats fact and if so how much or little.
My guess is its minuscule and the risk isnt worth the gain.
Would be a good episode for Myth Busters. Lol



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It would. Great idea actually. I have seen comparisons where the 0-20w oil does get just a tad better mileage. For an auto maker of course, when you multiply that tad by the number of cars they make, it becomes significant in the percentages. For the individual owner, I don’t think it is significant at all. It is similar to the auto start/stop debate. How much gas does that really save? Depends on the driver and on how long and how often the engine shuts down. But with the route and type of driving that the EPA route uses, it saves a tad amount of gas again. Across a whole production line that adds up and the incentives that the EPA gives the auto makers for that makes it worth it to them. It is one way that the Feds are able to direct tne way that the auto makers go. The same with 0-20w oil. Without the incentives i honestly doubt that any auto makers would use it. The fuel savings are not worth the potential engine damage. I know that this isn’t discussed a lot, but you can find some pretty technical discussuions on it if you look around. I read from a lot of people that change to 5-30w oil as soon as the warranty expires, or earlier in a lot of cases.

Now, i want to add that if you look around you can find sources that will say that 0-20w oil is perfectly safe and will not cause engine damage. There really is no consensus and i don’t think there is any way to “know” for certain. You just have to do your own research and follow your own findings.
 

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2019 Crosstrek 2018 Forester XT
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Now, i want to add that if you look around you can find sources that will say that 0-20w oil is perfectly safe and will not cause engine damage. There really is no consensus and i don’t think there is any way to “know” for certain. You just have to do your own research and follow your own findings.
I would add though that the auto designers and builders have designed their equipment to work with 20 weight. Larger bearing surfaces and smaller loads.

The lack of consensus is based on arguments between parties that have not designed the engines.
 

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Discussion Starter · #16 ·
I would add though that the auto designers and builders have designed their equipment to work with 20 weight. Larger bearing surfaces and smaller loads.

The lack of consensus is based on arguments between parties that have not designed the engines.
I agree with this statement very much. To suggest that engine is always protected better with a heavier weight oil may be very very wrong. Tolerances today are much tighter, passageways smaller, and the engines are designed to run with a film of modern oil that was never possible 20 - 30 years ago. Today's oils are so much better, especially in an engine designed for them. An engine designed for thin oil may not be able to even benefit from heavier oil and worst case scenario, the heavier oil may not pump or flow as well as the lighter oil.

But my original post was not aimed at discussing viscosity issues, though those are also valid, especially when an engine is being asked to run at the extremes of its design. So people racing in a desert or starting an engine in Fairbanks have very valid reasons to deviate from the manufacturers viscosity recommendations. Probably not the rest of us, in a relatively modern engine.

Thanks again for the civil discourse, and I welcome more of it. Happy New Year!!
 

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As a newbie Foz (& Scooby) owner, I really appreciate the knowledge and opinions shared in these discussions, particularly as my next oil service is due!!
 

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2019 Crosstrek 2018 Forester XT
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As a newbie Foz (& Scooby) owner, I really appreciate the knowledge and opinions shared in these discussions, particularly as my next oil service is due!!
I started this discussion over at bitog:
https://www.subaruforester.org/vbulletin/newreply.php?do=newreply&p=7485175
The discussion centered on using a 20 wt. oil of my 2018 Forester XTfor a short period of time driving 2 set courses multiple times under the same conditions. Once I determine the mileage per gallon I will dump half the QSUD and add 0W-40 Mobil European formula and drive the next 6 months with it..checking mpg and then doing a used oil analysis at the end.

I won't say much more on that other thread as there are a number of people there that feel its their duty to show how intelligent they are and how ignorant I am. Fine. That works for me.

The blog listed below indicated how 225 oils fared in load tests. I selected the QSUD in part based on that. Valid or not I reasoned that the oils here are API certified (for the most part) so it seemed reasonable to select an oil ion the upper 10% . So check it out and select your oil based on your own determinations.

https://540ratblog.wordpress.com/

Happy New Year from the U.S.
 

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Is there any reputable source that backs that up ?
Id really love to know if thats fact and if so how much or little.
My guess is its minuscule and the risk isnt worth the gain.
Would be a good episode for Myth Busters. Lol
I can confirm this (works for a vehicle manufacturer). Based on some slides I've seen at work, a thinner oil will account for a 0.XX% fuel economy gain, give-or-take b/c our engines are not very comparable to a Subaru engine. It's not a huge gain, but it's low hanging fruit for engine manufacturers because, in theory, you don't have to change any other components to run a thinner oil (although the statements above re: Toyota show this isn't really the case).


I am currently running my 2018 XT on 20 wt. I will just be doing it for cool weather and will only do it for a couple weeks. I have done 9 10 mile trips all under similar conditions Oil temp, speed, and terrain. Mileage averages 35.2 mpg. Of course I don't use boost and won't with the 20 wt. 30 wt averaged 32.3 mpg. So its north of 6% improvement. The FA engine was designed for 20 wt and a Compression ratio of 12.5 the boosted version is only 10.6. and calles for 30 wt. oil. So running with no boost, in cooler weather. No reason to worry. And it will be short term. I did it out of curiosity. :)
Trips that short (10 miles in cold weather) mean you are running a "severe" duty cycle and should be doing frequent oil changes anyway. Severe duty really beats the snot out of your oil.

As far as your 6% difference in mileage numbers, I would take that number with a grain of salt. Not just because your experimental setup is flawed, but because I have seen the actual numbers published by Shell, etc., and the difference is much lower, >1% from a thicker viscosity to a thinner one.

Some things that can affect FE numbers:

Winter vs. summer fuel
Weather conditions (air temp, humidity, altitude, etc.)
Road conditions (wet, dry, windy, hills v. flat etc.)

I'm not trying to be a jerk, just pointing out that your testing shows a much greater benefit than any lab/field testing I've ever laid eyes on.
 

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As far as your 6% difference in mileage numbers, I would take that number with a grain of salt. Not just because your experimental setup is flawed, but because I have seen the actual numbers published by Shell, etc., and the difference is much lower, >1% from a thicker viscosity to a thinner one.

Some things that can affect FE numbers:

Winter vs. summer fuel
Weather conditions (air temp, humidity, altitude, etc.)
Road conditions (wet, dry, windy, hills v. flat etc.)

I'm not trying to be a jerk, just pointing out that your testing shows a much greater benefit than any lab/field testing I've ever laid eyes on.
I totally get what you are saying and I am surprised myself.

But my testing is pretty defined and exact. I run 2 similar courses in outside temperatures between 35 and 45. The oil temp is always between 185 and 192F. The loops are very rural and so the times and speeds are repeatable. The trip length is 9 miles and the trip length is 13 minutes. I realize it is not "real world driving". But it very closely shows the contribution of oil thickness. I have decided to keep the oil in at least another 100 miles to pin it down even closer. Then I will re-run the course many times (again) with 30 wt oil.

Like I said I am very surprised.
 
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