20,000 Mile Oil Change Interval?

[Al]

2022 Forester-33,500 Miles on Odometer. After 10K miles on my current oil change, I just sent in an oil sample-Mobil1 5W-40. I had previously done a 5K mile UOA with 5W-30. Ran a 2K short Oil cycle and then my current sample with 23K miles on the vehicle. The filter is a 7317Titanium and I placed strong magnets around the filter.

I was reading some SAE Papers from early 90's that gave results of UOA's 20K miles and above for Diesel tests. For Gasoline I had only Papers dealing with VE Sequence testing. Diesel OCI's range in the 100K mile OCIs are normal.

With all the knowledge on the BITOG board its clear that a 20K uoa is not going to affect longevity of engine life. Why do I see so few of UOAs in this range? Fear of loss of warranty? The fact that "Auto Engineers know best"? Habit? Just curious.

 

[buster]

Some GDI engines beat up oil pretty good.

 

[Rand]

With all the knowledge on the BITOG board its clear that a 20K uoa is not going to affect longevity of engine life. Why do I see so few of UOAs in this range? Fear of loss of warranty? The fact that "Auto Engineers know best"? Habit? Just curious.

Subarus are not a good candidate. The GDI motors are fairly rough on oil and all the quirks of being a boxer engine.
They previously spec'ed the fb25 7500miles, it was reduced to 6000... and that was before GDI.

I have to believe if there were NO concerns they would try to raise that to at least 10000 miles.

My winter oil comes out like black water at <4000 miles and smells of gas but not excessively.
In the summer I try to run 5000 or 6000 oci's

With the proper oil and long highway miles I am sure their numbers are conservative.
otherwise just about right IMO.

 

[Al]

Subarus are not a good candidate. The GDI motors are fairly rough on oil and all the quirks of being a boxer engine.
They previously spec'ed the fb25 7500miles, it was reduced to 6000... and that was before GDI.

I have to believe if there were NO concerns they would try to raise that to at least 10000 miles.

My winter oil comes out like black water at <4000 miles and smells of gas but not excessively.
In the summer I try to run 5000 or 6000 oci's

With the proper oil and long highway miles I am sure their numbers are conservative.
otherwise just about right IMO.

My experience is different than yours. I did multiple 10K oi lchanges on my 2008 Forester and my daughters. Mine was still on the road at 280 K miles when my granddaughter sold it. Both were switched to 40 wt oil. Hers got wrecked at 140 k miles. Also my Forester is on 5W-40 oil. I would not do this with 20 wt. oil although neither will I say it could NOT go the distance.

UOA's on here and on subaru boards demonstrate that Subaru engines are very easy on oil.

 

[MParr]

Diesel engines in over the road trucks can easily do 20,000 mile oil change intervals. They have much larger sumps than passenger cars. If you want to risk it, have at it.

 

[SwampSurvivor]

Subarus are not a good candidate. The GDI motors are fairly rough on oil and all the quirks of being a boxer engine.
They previously spec'ed the fb25 7500miles, it was reduced to 6000... and that was before GDI.

I believe they dropped the change interval because too many people ran their FB20 and FB25 out of oil on the longer run. The GDI engines don't have the oil consumption issues that the early FBs had.

Granted, longer drain intervals on a GDI engine with timing chain(s) is probably not the best idea.

 

[twX]

I was reading some SAE Papers from early 90's that gave results of UOA's 20K miles and above for Diesel tests. For Gasoline I had only Papers dealing with VE Sequence testing. Diesel OCI's range in the 100K mile OCIs are normal.

There are some good studies for gasoline engines. SAE 870043 is a GM study that seems to be the basis of their oil life monitoring system. Maximum OCI was determined to range from 4k km to 16k km, based mostly on trip length. That was with an API SF oil of mediocre quality. SAE 932838 is another GM study that's a bit more recent.

A more modern study that includes GDI engines, 2013-01-2607, looks at statistics regarding when an OLM on some vehicle models recommends that the oil be changed. It ranges from 6k km to 40k km for vehicles in a mild climate.

It seems that your average vehicle can go 10k miles safely, but many can't, and 20k+ mile OCIs require conditions to be close to ideal. It's a matter of risk vs reward. Extending an OCI from 10k to 20k miles introduces a lot of risk without reducing the operating costs of the vehicle very much.

By not following Subaru's 6k mile OCI requirement, you're risking a warranty denial for a $5k+ repair job in order to save $150 on the cost of oil changes over the warranty period. If you're lucky, you won't need the warranty or it won't be denied, but you may still end up with a less healthy engine if you extend the OCIs too much. Is it worth it?

 

[Rand]

My experience is different than yours. I did multiple 10K oi lchanges on my 2008 Forester and my daughters. Mine was still on the road at 280 K miles when my granddaughter sold it. Both were switched to 40 wt oil. Hers got wrecked at 140 k miles. Also my Forester is on 5W-40 oil. I would not do this with 20 wt. oil although neither will I say it could NOT go the distance.

UOA's on here and on subaru boards demonstrate that Subaru engines are very easy on oil.

The EJ series is not the FB series
Also specifically The 2019+ with GDI are what I was talking about. Its your vehicle but the risk/reward is low IMO.
Esp. considering they reduced the sump from 5.75qt in my 2011 to only 4.4qt now in the 22.
I'll keep doing my $12 syn oil changes.
Also suggest a CVT drain and fill and gear oil in both axles. at your mileage. IF doing it yourself the gear oil is fairly easy and the valvoline squeeze bag makes quick work of the refill. I would suggest 4 ramps and a breaker bar for the first time loosening the plugs they can be TIGHT.
The initial gear oil change comes out gross looking.

 

[nicholas]

2022 Forester-33,500 Miles on Odometer. After 10K miles on my current oil change, I just sent in an oil sample-Mobil1 5W-40. I had previously done a 5K mile UOA with 5W-30. Ran a 2K short Oil cycle and then my current sample with 23K miles on the vehicle. The filter is a 7317Titanium and I placed strong magnets around the filter.

I was reading some SAE Papers from early 90's that gave results of UOA's 20K miles and above for Diesel tests. For Gasoline I had only Papers dealing with VE Sequence testing. Diesel OCI's range in the 100K mile OCIs are normal.

With all the knowledge on the BITOG board its clear that a 20K uoa is not going to affect longevity of engine life. Why do I see so few of UOAs in this range? Fear of loss of warranty? The fact that "Auto Engineers know best"? Habit? Just curious.

A lot depends on driving style and environment....
I'm in freezing cold Canada...it takes me 4 years to drive 20k miles.....no way am I keeping oil in there for that long.

 

[The Lube Guy]

Some GDI engines beat up oil pretty good.

It's not so much the GDI engines, as it is the "driving style" of the owners. You have to treat a GDI engine a little bit more like a Diesel engine without forced induction, and you will be fine. Short tripping a vehicle with a GDI engine is a big no-no, amongst other things.

 

[Al]

Thanks for the comments. The only "Reward" is just looking at the UOA's and verifying that what I am doing. Makes sense environmentally at a savings of effort by me.

No concere about warranty issues. They don't exist for me. I welcome them trying to deny any warranty.

I really expect great UOA results. I plan on doing the same on my '18 Forester. It will t ake the better part of 3 years to put 20K miles on it. It only has 40K miles on the clock now.

 

[cptbarkey]

2022 Forester-33,500 Miles on Odometer. After 10K miles on my current oil change, I just sent in an oil sample-Mobil1 5W-40. I had previously done a 5K mile UOA with 5W-30. Ran a 2K short Oil cycle and then my current sample with 23K miles on the vehicle. The filter is a 7317Titanium and I placed strong magnets around the filter.

I was reading some SAE Papers from early 90's that gave results of UOA's 20K miles and above for Diesel tests. For Gasoline I had only Papers dealing with VE Sequence testing. Diesel OCI's range in the 100K mile OCIs are normal.

With all the knowledge on the BITOG board its clear that a 20K uoa is not going to affect longevity of engine life. Why do I see so few of UOAs in this range? Fear of loss of warranty? The fact that "Auto Engineers know best"? Habit? Just curious.

This will be an interesting UOA to see the long term fuel dilution effects, if any.

 

[Yolo]

I know I’m late to the party but if I was doing 20k mile oil changes on my vehicle I’d most definitely be using HPL engine oil.

I don’t because I’m in warranty and also because I enjoy working on my truck - so even past warranty, I’ll be doing 4-5k OCIs. Big city traffic is tough on equipment.

 

[goingplacesanddoingstuff]

20k is probably a lot easier to achieve safely if all the miles are highway.

 

[Cary]

2022 Forester-33,500 Miles on Odometer. After 10K miles on my current oil change, I just sent in an oil sample-Mobil1 5W-40. I had previously done a 5K mile UOA with 5W-30. Ran a 2K short Oil cycle and then my current sample with 23K miles on the vehicle. The filter is a 7317Titanium and I placed strong magnets around the filter.

I was reading some SAE Papers from early 90's that gave results of UOA's 20K miles and above for Diesel tests. For Gasoline I had only Papers dealing with VE Sequence testing. Diesel OCI's range in the 100K mile OCIs are normal.

With all the knowledge on the BITOG board its clear that a 20K uoa is not going to affect longevity of engine life. Why do I see so few of UOAs in this range? Fear of loss of warranty? The fact that "Auto Engineers know best"? Habit? Just curious.

You are mixing a lot of issues and then jumping to conclusions. Briefly:

1) You cannot compare OCI for over the road diesel trucks, designed with huge sumps and filtration systems for 50k intervals with a gas powered daily driver.
2) One size does not fit all. A car with 2.0 liter, turbocharged direct injected, 300 horsepower engine with a 4 quart sump driven only on short trips is going to have a far different interval than something with a lowly stressed 3.5L V6 port injected putting out 200 horsepower with a 7 quart sump and driven only on long trips on the highway at 70mph.
3) You make a huge leap going from finding a 10k interval works on your car to trying a 20k interval. What did the TBN look like at 10k? What was the fuel dilution? If in fact you are going to try running your oil to 20k, I would suggest you pull samples every 2,500 miles past 10k and monitor, so you can see where the drop-off occurs.

I am a fan of running longer intervals than most here. I run 10k on most of my vehicles and have for 20 years (on synthetics). That said, once you are beyond the manufacture's intervals, you really do need to work your way up with testing to see what the safe limit is, and even then, should leave some cushion.

 

[Al]

You are mixing a lot of issues and then jumping to conclusions. Briefly:

1) You cannot compare OCI for over the road diesel trucks, designed with huge sumps and filtration systems for 50k intervals with a gas powered daily driver.
2) One size does not fit all. A car with 2.0 liter, turbocharged direct injected, 300 horsepower engine with a 4 quart sump driven only on short trips is going to have a far different interval than something with a lowly stressed 3.5L V6 port injected putting out 200 horsepower with a 7 quart sump and driven only on long trips on the highway at 70mph.
3) You make a huge leap going from finding a 10k interval works on your car to trying a 20k interval. What did the TBN look like at 10k? What was the fuel dilution? If in fact you are going to try running your oil to 20k, I would suggest you pull samples every 2,500 miles past 10k and monitor, so you can see where the drop-off occurs.

I am a fan of running longer intervals than most here. I run 10k on most of my vehicles and have for 20 years (on synthetics). That said, once you are beyond the manufacture's intervals, you really do need to work your way up with testing to see what the safe limit is, and even then, should leave some cushion.

Yes comparing a 12 gallon sump of a diesel engine to a 5 quart sump of a car. is not very valid but it is still extended drain in the order of 10K miles.
Both the turbo FA20 and NA FB25 sumps are 5 quarts. I have yet to see a low TBN on a UOA. I will check it at 20K. I will pull a sample at 15K miles. I may or may not get it read. Pulling the sample is insurance in case the engine has a problem be tween 15 and 20 K miles. Depending if a Sample looks good at 20K I will go to 25K miles.

 

[Glenda W.]

I would love to see your uoa’s during the process to 20k. I have a 2018 Outback 2.5 non gdi. I can’t keep the oil in grade past 6000 miles. I believe the long timing chains are hard on oil. My next fill is with Amsoil SS and will see how it holds up.

 

[Lavrishevo]

Worst idea ever. I’m at a loss why people do this. You are a 1000% better using cheap oil and regular 5k OCI’s vs boutique oil and extremely long intervals. A UOA will not show what is happening with slugging and carbon buildup around the oil rings on the pistons. This will eventually cause that ring to seize and start scoring the **** out of your cylinder wall. This video was geared towards Toyota Lexus owners, but the same thing applies to Subarus. Not to mention how hard a turbo is on oil in general. OP, I seriously suggest you watch this video and reconsider your strategy. This guy is a well-known master mechanic makes a lot of really good videos.

 

[buster]

Worst idea ever. I’m at a loss why people do this. You are a 1000% better using cheap oil and regular 5k OCI’s vs boutique oil and extremely long intervals. A UOA will not show what is happening with slugging and carbon buildup around the oil rings on the pistons. This will eventually cause that ring to seize and start scoring the **** out of your cylinder wall. This video was geared towards Toyota Lexus owners, but the same thing applies to Subarus. Not to mention how hard a turbo is on oil in general. OP, I seriously suggest you watch this video and reconsider your strategy. This guy is a well-known master mechanic makes a lot of really good videos.

It's not that simple though. While some engines won't tolerate longer intervals, some will. The higher end boutique oils like HPL, Amsoil and Mobil 1 are built to handle longer drains and will keep rings clean. The solvency and dispersant/detergent package built into the oils like HPL/Amsoil are what keep pistons clean.

 

[Lavrishevo]

It's not that simple though. While some engines won't tolerate longer intervals, some will. The higher end boutique oils like HPL, Amsoil and Mobil 1 are built to handle longer drains and will keep rings clean. The solvency and dispersant/detergent package built into the oils like HPL/Amsoil are what keep pistons clean.

In theory, and it is somewhat engine specific, but why risk it? Particularly Subaru engines that are known for fuel dilution. Not to mention voiding your warranty. Risk mitigation. Oil is cheap, especially for enthusiasts who often do it themselves. It’s unfortunate that marketing often trumps reality. I use higher end oil, but absolutely stick to 5k OCI’s even if I could go longer I know my engine will last longer, particularly high mileage. I know my internals will be sludge free. I had a WRX for a bit and know how hard these motors are on oil.