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2020 Outback Limited 2.5i
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106 Posts
You've got me beat in overall gas mileage, nicely done!
Thanks! And I just had my best tank at 36.8 mpg! I've been working from home but had to go into work every day last week. With the warmer weather, summer gasoline, and lack of traffic, the fuel economy improved nicely.
 

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2020 Outback Onyx XT
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3,631 Posts
7-11 sells gas? We have 7-11's but none of them that I know of have pumps.

The one 45 minutes away is Exxon, I think. The store isn't branded Exxon (Top Star or something) but there's Exxon stickers on the pumps. I do get out there every couple weeks and fill up there every time I do. I also know of a Sunoco branded station about the same distance, but in a different direction and I almost never get over there. I also have 3 costco's all about an hr away.

I'm in Wawa vs Sheetz territory and those 2 absolutely dominate the gas station scene. And they keep on building more and expanding the existing ones. Rutters and Turkey Hill have a presence too, Rutters is growing fast in the area. Plus a lot of grocery stores sell gas.

I'm pretty sure Sunoco is the regional distributor that sells to all of the above. But that doesn't mean it has Sunoco additives.
The one near me is a 7-11 and Philips 66 joint operation:

485711
 

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2020 Outback Onyx XT
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124 Posts
...They all advertise that they buy gas from the Exxons and Sunocos of the world, and then add detergents.

I believe, but am not sure, they are put in when the gas is on the truck, as ALL brands fill their truck from the same place in a given area. Yes, Sunoco might use Exxon gas here, and somewhere else, Exxon uses Sunoco. And Wawa is using the same thing.
That's because most gas stations only have two tanks - one for regular and and one for high octane. Then at the pump you might have four choices so they mix them together. Anything that has any from 2nd tank is marked as premium..
Fact:
I did not read this entire thread. I only read the last page or two.
Fact:
@pcray1231 and @Stuff are both right, at least for many stations in Missouri.

My wife, for nearly 30 years, has been the office manager for a family owned company. That company owns 5 convenience stores. The also sell and deliver bulk propane and fuel for residential, farm and commercial use, even to other gas stations. Three of their stores are branded BP, one is branded Amoco, and one is "unbranded". (For the record in case anyone did not know or forgot, BP bought out Amoco many years ago, but they are bringing the Amoco branding back.) Most of their fuel is picked up by their own tanker trucks and drivers at the depot. During especially busy times of the year, think planting/harvest season, they may have some of the fuel delivered by contract haulers. (Yes...they sell a ton fuel in the boonies of Missouri.) The fuel is loaded on the truck and then the additive package gets added to the truck. The base fuel of any given octane is all the same regardless of who the buyer is or where the final destination is. As stated before, only the additive package is different.

I cannot remember the details for each of their stations, but in most cases, they do actually have separate tanks and pumps for each octane of fuel. That said, at least one does exactly as @Stuff says and they have two tanks. One base octane, one premium, and then they have a pump that pulls and mixes from both for the mid grade. The only real difference is at one station the premium fuel has no ethanol in it.
 

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6 Posts
Subaru recommends 87 octane or higher in this engine. This is my first Subaru. I am used to running premium in my cars (German recommendation). Because I'm still in the break-in period (which is a whole other discussion about how to do it, and for how long?), I am not spooling-up the engine/turbo, so it's hard to tell performance-wise. I've started by using mid-level (89 octane) Chevron gas. What do you do with your 2.4L turbo, and why?
 

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'20 Outback Onyx XT AGM/'04 Forester XT
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397 Posts
There a two thought camps on this. Some say that there is no benefit in running anything higher than 87 since that is what is recommended. Others that have had turbo Subaru's before run 91 or higher since that is what was previously recommended by Subaru and 2.4T owners are guinea pigs since this is a new engine. :) There's an ongoing thread here about it somewhere.

When Cobb Tuning was developing an AccessPort for the Ascent (it also has the 2.4T), they noted that there was some pinging on 87 but didn't provide any further comments. The owner's manual says some pinging is normal.

Here's the thread:

 

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Also some food for thought is the station you fill up at. @Robert.Mauro and I had a lengthy discussion on the Ascent forums (uses the 2.4 also) about the detergent and additive packs for the gas stations.

I believe we determined that Shell 93 is the best premium and the Costco 87 is the best regular.
 

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2020 OB Limited, Titanium & Magnetite Grays
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1,345 Posts
Top tier gas is mostly the same until there is objective data to the contrary, so buy Top Tier at the best price (Costco but not Sam's because it is NOT top tier). A consideration is when living at high altitude the gas octanes have been decreased but for a turbo the standard recommended octane, 87, should be used when available.
 

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Correct, there is a baseline additive number to qualify as top tier, but Costco’s 87 and Shell’s 93 have the “most” additives exceeding the baseline.
 

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2020 Onyx
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12,657 Posts
I use shell v-power 92 (that's the best available in my area).

My reasons are these:

The aforementioned "normal" knock that I want to avoid, which may pull timing just a bit.

Decreased potential for LSPI (which is not spark timing dependent)

Increased detergency for the GDI fuel injectors

Decreased potential for ring-land failure

I'm NOT doing it for "increased power" or "better fuel economy"

It's purely a defensive measure for me, like the reasons why I choose to go with 3k oil change intervals on a turbo motor with potential for fuel dilution of the engine oil, soot accumulation in the oil. I'm just doing overkill.

I didn't want to share this publicly, but this is my second Onyx XT. My first one had what seemed like sudden catastrophic engine failure after owning it for one week. It literally could not be driven. My dealer gave me a loaner, then after a week, arranged to get me a new replacement car without me even asking for it. Nobody else has had this experience that I am aware of, but it's made me gun-shy about this engine. I'm babying it with regard to fuel and oil, but otherwise I just drive it normally, not afraid of going full throttle up hill for example.
 

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I’m glad you had a good experience in what would have otherwise expected to be a lousy situation.

Regarding the 2.4 engine, it is my opinion that if you fill up at a top tier station you shouldn’t need to add some type of fuel system additive like Techron to your tanks; but this has no effect on carbon buildup on the intake valves. Oil has a lot to do with carbon buildup and I think your 3000 mile oil change is an excellent idea. Specifically, the NOACK values of oil are an indicator and measurement of volatility and proneness to vaporizing which is what cakes on your valves. Regarding LSPI, it appears that the next iteration of oils - SP - is being specifically formulated to combat that.


Aside from increased operating cost I don’t think the 93 would be detrimental to the vehicle - but every once and a while I hear stories or articles about the fuel not burning completely which allegedly results in unburned gasoline either doing an EGR cycle or going through your exhaust system.

If I end up going for an XT I might seriously consider doing a DIY 3000 interval - even if that means I leave the filter on and just drain the oil out and refill it. At dealer prices of $65 by me for oil only, I’d be looking at a potential increase of $130 per year.

Also, just something to also think about, new variants of engines have had their share of issues across all manufacturers. The Forester (2019+, 2.5 FB25DI) had some issues when first produced relating to the PCV failing due to shoddy supplier components and it grenaded a bunch of engines. They recalled it. My Forester was built in December of 2019 and was not included in the recall so they got a handle on it quickly.

The two vehicle related things that keep me up at night on these cars are the CVT and fluid change interval and the direct injection carbon buildup. I don’t mind the carbon as much because that is a relatively cheap fix but the CVT typically costs more to repair than the value of the car. If the Mrs. was more on board with an EV I would prefer to go that route (though I would have a new type of boogeyman keeping me up at night..)
 

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2010 Subaru Outback Premium 2.5i w/AWP 6MT
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450 Posts
Also some food for thought is the station you fill up at. @Robert.Mauro and I had a lengthy discussion on the Ascent forums (uses the 2.4 also) about the detergent and additive packs for the gas stations.

I believe we determined that Shell 93 is the best premium and the Costco 87 is the best regular.
Yep, pretty much.
 

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2010 Subaru Outback Premium 2.5i w/AWP 6MT
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450 Posts
and the direct injection carbon buildup
I want to have my engine scoped one day. If any FA24F is going to have carbon buildup, it's likely to be mine... not that I abuse the heck out of it regularly or anything. :LOL::ROFLMAO:

I gotta save up for it, or start a gofundme or something, lol.
 

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Haha, I would kick in a few bucks in the name of “science!”

I don’t mind if I had to scope them but I’ve heard that they’ve been solid. The FXT and WRX have had some issues apparently but they are looking good - though in the US market they’ve only been in the Forester since Model year 2019.
 

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2020 Subaru Outback XT Limited
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74 Posts
I now have 15,000 miles and here is my experience. For the first 1,500 miles I filled with 87 octane. It ran fine, didn't notice anything unusual. I had planned on every 4th tank to put 91 to help keep the injectors clean. After putting in 91 the car ran quieter and smoother both at idle and during acceleration. Went back to 87 and the smoothness went away. Put in 89 for 4 tanks. No change in economy and no smoothness. Went back to 87 for 4 tanks then 91. Car ran smoother and quieter. No change in economy. Side note. Trip Odometer B set the day I bought it. Computer says car is getting 20.4 mpg average. I live in Austin TX.
Recently took a road trip to Prescott AZ via Albuquerque NM, Flagstaff AZ. Same (Shell) gas. Got 25 MPG to Albq NM. Filled up and got 32 all the way to Prescott AZ. Dove in Prescott and got 29 in town. Drove home via Phoenix, El Paso TX. Got 30 to El Paso. Filled up in El Paso and got 25 all the way to San Antonio TX. Same brand, same octane. I was thinking altitude played a part. But Phoenix to El Paso no real altitude change. I will be moving to Prescott at the end of the year. If my economy improves on a daily basis then I will assume there is something with TX gas, like California gas and all the anti pollution stuff they have there. Lived in Cali, SD and SAC for 15 years. Gas there robs economy.
 

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2020 Outback Limited 2.5i
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106 Posts
Are there any good detergent additives that we can add to our fuel?
I assume you are referring to an aftermarket additive. Based on testing I've performed and seen (at my last job), I see no need to put any aftermarket fuel additives in my outback and I'd feel the same way if I had the XT turbo engine. None of the aftermarket additives will affect intake valve deposits and the direct injectors will stay clean with the minimum of detergent.

The only time I've used an aftermarket bottle of additive was once every 5 tanks in a 1976 Honda GL1000 as it had a tendency to build up some carburetor deposits and the aftermarket bottle seemed to help.
 

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2020 Onyx
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12,657 Posts
I assume you are referring to an aftermarket additive. Based on testing I've performed and seen (at my last job), I see no need to put any aftermarket fuel additives in my outback and I'd feel the same way if I had the XT turbo engine. None of the aftermarket additives will affect intake valve deposits and the direct injectors will stay clean with the minimum of detergent.
Sorry to bring this up again but the detergent treat rates seem to matter:



From Fuel Tanker Driver Here

That's why I recommend top tier at a minimum and for myself choose the premium with the highest treat rate of detergents, out of an abundance of caution. A dirty GDI injector contributes to fuel dilution in the oil - a double whammy.
 

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2020 Outback Limited 2.5i
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Sorry to bring this up again but the detergent treat rates seem to matter:



From Fuel Tanker Driver Here

That's why I recommend top tier at a minimum and for myself choose the premium with the highest treat rate of detergents, out of an abundance of caution. A dirty GDI injector contributes to fuel dilution in the oil - a double whammy.
I actually made that chart when I worked at BASF. I'm not sure how it leaked to the internet but that's not my problem anymore. This chart is in regard to differing treat rates of the same additive, BASF's Keropur AP-205-20, in retail gasoline. It is not an aftermarket treat rate. Most aftermarket bottles treat at a much higher rate, perhaps around 180 to 500 ptb (pounds per thousand barrels). Every gallon of gas sold in the U.S. has a minimum amount of detergent. Based on 12 years of experience testing retail and aftermarket additives in more than 100 different engines and vehicles, no one needs to add an aftermarket bottle of additive to retail fuel. There's just no benefit. That chart was created so fuel marketers would know which claims BASF could support with data should they want to make the claim that "our fuel cleans up intake valves" or whatever they wanted off of the chart. I know the tests behind each of those claims in depth because I designed and ran those test programs for BASF.

At my job before working at BASF, I also tested additives. We were hired by a fuel retailer to find used cars with dirty valves and fouled port fuel injectors. We borescoped over 100 used PFI cars and found none with an amount of intake valve deposits worth cleaning up. We also pulled swapped out port fuel injectors on over 20 vehicles and flow tested them, they were all fine. None were fouled. Every used used PFI car I've ever borescoped, which is probably over 200, never had any significant intake valve deposits. In order to show a clean up, we'd have to use a severe fuel or a doped severe fuel to create intake valve deposits in order to show a cleanup with an additive.

Of course, GDI intake valves are a different story but nothing in the fuel is going to clean up a GDI intake valve because the fuel never hits the back of the valve. We did evaluate GDI fouling on several older high mileage cars from the mid to late 2000's and some of them had a small amount of GDI injector fouling. Nothing that would cause problems though. Later model years of the same cars, that had updated injector design, showed very little to know direct injector fouling.

I'll also add that there is no standard test for GDI fouling so each additive company (BASF, Afton, Lubrizol) are doing their own thing. TOP TIER is working on a test but it's not complete. The CEC folks in Europe also have a partially complete test.

After 12 years of testing gasoline and additives, I buy the cheapest gas I can find whether it's LAC or not. Seeking out Shell or Exxon fuel and buying Premium isn't worth the extra cost. Now, I don't own the XT. If I did have an XT, I'd probably try a tank of premium every now and then but wouldn't make a habit of it and would be more concerned with the oil that I used. Turbo coking is a problem so I'd be sure to use a DEXOS2 approved oil as that oil has to pass pretty stringent turbo coking test.

However, as with anything, go buy whatever you want! If it makes you feel better and reduces stress, then go for it!
 

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'20 Outback Onyx XT AGM/'04 Forester XT
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I actually made that chart when I worked at BASF. I'm not sure how it leaked to the internet but that's not my problem anymore.
It's actually on Magellan's web site:


jholmes8 said:
Of course, GDI intake valves are a different story but nothing in the fuel is going to clean up a GDI intake valve because the fuel never hits the back of the valve. We did evaluate GDI fouling on several older high mileage cars from the mid to late 2000's and some of them had a small amount of GDI injector fouling. Nothing that would cause problems though. Later model years of the same cars, that had updated injector design, showed very little to know direct injector fouling.
When Subaru's DIT first appeared in the WRX people started having walnut shell blasting based on pictures of very minimal intake valve buildup. Some are also doing it as preventative maintenance based on those pics as well as what people are saying on forums. In most cases, I don't recall if people have mentioned real drivability problems with having CEL's/MIL's. Most comments are based on butt dyno feel. None of the pics of Subaru intake valves with carbon buildup that I have seen are nowhere the level of buildup on VAG's or BMW's from several years ago. Not even close.
 

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2020 Outback Limited 2.5i
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It's actually on Magellan's web site:




When Subaru's DIT first appeared in the WRX people started having walnut shell blasting based on pictures of very minimal intake valve buildup. Some are also doing it as preventative maintenance based on those pics as well as what people are saying on forums. In most cases, I don't recall if people have mentioned real drivability problems with having CEL's/MIL's. Most comments are based on butt dyno feel. None of the pics of Subaru intake valves with carbon buildup that I have seen are nowhere the level of buildup on VAG's or BMW's from several years ago. Not even close.
Just pointing out that you highlighted my text on GDI injector fouling, which is different from GDI intake valve deposits, which you are referring to. In regards to GDI intake valve deposits, I have seem some valves on test engines that look like these from an Audi but the engine still operated fine with no hesitations or stumbles:

488470


The engine in question was a GM LHU (2.0L GDI-T) so forced induction has a way of not caring about some valve deposits. The air will get through as its under pressure.

And I agree, the early BMW's and VAG's were terrible. More recent engines and OEM's have done a better job of eliminating oil mist, reducing EGR, etc. so that the deposits aren't so bad. Minimal buildup on a WRX GDI-T engine isn't worth cleaning unless you are racing and need every last bit of power.
 
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