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Discussion Starter · #1 ·
A couple questions for our all knowing forum regulars and anybody else that wants to chime in.
Do ANY fuel additives do any good, that is, clean injectors, keep valves clean, keep fuel systems running "better"?
Or is running top tier fuel in the gas tank good enough these days?
If there are any that work, what are they?
I know gasoline is a lot better quality now than when I started driving 50 years ago. Is there cleaning agents in economy gas, even though it's not advertised as such?
 

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Pre-Ascent I used to use King Soopers fuel stations for the discount and convenience. I ended up with more than my share of fuel problems so I stopped purchasing fuel there. I can still use the discount at a Shell station which is a top tier fuel. I only use top tier now and have continued with the Ascent and my other vehicles using the top tier. The Ascent needs 87 octane regardless of top tier or not.

I would not bother with any additional additives beyond what comes with a top tier fuel. I have not found the top tier fuel to be any more expensive than the other type of fuel comparing the same octane.
 

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The Ascent uses Direct Fuel Injection. The fuel is injected directly into the cylinder and does not run by the valve so fuel additives will not clean the valves. They will clean the injectors if it is needed.

Top Tier fuels have additives that are designed to be good enough. Top tier fuel can be found at cheap prices. Costco and Valero are both inexpensive brands that are top tier. My problem is there are not always stations near me that have top tier fuels. So while I strive to use only top tier fuel it does not always happen.

I use Lucas fuel injection cleaner at every oil change. Does it really help? I honestly can’t tell the difference which means it can be helping or not really helping . My injectors do stay clean on my cars for the 100k-300k I usually keep a car for.
 

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I've been driving since the mid-late 1970s and I cannot remember every using a fuel additive on any vehicle I've owned. Like Packout and others, I pretty much stick to top-tier fuel (almost 100% Costco for me unless traveling) and don't worry about it.
 

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I have a ton, and I mean a ton, of miles on Speedway (Crystal Flash) gas and I have never used any additives. Knock on wood, zero issues with multiple vehicles in the 6 digit mileage range.
 

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So far I've only used top tier, Costco in the Ascent. Once we start traveling again, I'll keep a couple of bottles of Tecron on hand (also available at Costco) for fillups where top tier isn't available.
 

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Some people swear by fuel additives, saying its a a miracle-in-a-bottle that'll fix knocking, rough idling, and your marriage all at once. Others write them off as mere snake oi that'll go into your wallet while you sleep and steal your credit cards. I'm somewhere in between. In older engines, I have noticed slight benefit when I started using them at higher mileage.

While the benefit to a direct injection engine would be significantly less, I don't think it is zero. Although the valves won't get cleaned, I do think there would be cleaning of the cylinder and piston. Chris-FIX, Project Farm, and some other youtubers have shown some slight cleaning of the pistons. I figured running an additive in the car from new should help prevent carbon buildup, so I'm willing to toss a few bucks in to hopefully extend the life of the engine.

I put an additive in the fuel every 1000 miles, and I rotate 6 different additives (so each one gets used once per oil change): Techron, Seafoam, Lucas, Redline, STP, and MMO. The 6 I chose are based on about 3 minutes of google searching, so there's no hard reason for those in particular.
 

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A couple questions for our all knowing forum regulars and anybody else that wants to chime in.
Do ANY fuel additives do any good, that is, clean injectors, keep valves clean, keep fuel systems running "better"?
Or is running top tier fuel in the gas tank good enough these days?
If there are any that work, what are they?
I know gasoline is a lot better quality now than when I started driving 50 years ago. Is there cleaning agents in economy gas, even though it's not advertised as such?
With direct injection, such products are completely useless.
 

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Discussion Starter · #13 ·
I have always tried to run top tier fuels in my cars.
This past year I was putting a bottle of Sea Foam in the Ascent and Forester just because I was driving one to work (about 50 miles a day) and the other did light duty in town driving as my wife needed it. I would rotate every week or so and the SeaFoam was mostly to keep the fuel fresh.
Years ago while living in Colorado, I had a good friend that owned a mom and pop tire store/muffler shop.
He swore by BG products, but this was also back when most cars were carburetor equipped. And I definitely understand the difference between the old V8s of yesteryear and the 4 cylinder boxer in the Subarus.
 

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BG did work great on carbureted engines back in the 70's when I worked at a gas station. I have not tried them on fuel injected engine. Their products are hard to find around me.
 

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Oh hell no. I pulled one plug for a change, and that was a nightmare. Anyway, it would be the intake plumbing I need to remove. So, unless someone is buying me new seals, then, I am not that interested it doing it. Especially not out in the cold. LOL!!! 🤣
 

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Fuel additives are used by Top Tier gas stations and this is precisely what sets them apart from non-Top Tier stations that do not use them to lower costs. Not counting any snake oil additives, they're mostly fuel detergents which absolutely do help, even for DI engines as they clean more than just the valves. They work over time, tank by tank, day by day, year by year. Simply adding a bottle now and then won't help much.

You should always use Top Tier gas stations simply because they include these additives. If you don't have easy access to a Top Tier station, then you can add these products yourself. Techron would be the best and safest choice. But you need to add them to every tank because the cleaning process must be constantly maintained.

If you simply use Top Tier gas stations, you do not need to add any other aftermarket fuel additives.
 

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How are the FA engines with carbon buildup? Will we need blasting every 60k or so?
There's no evidence of this. Subaru's current generation of DI engines now have millions of accumulated miles. If there was a significant problem, we would know by now.

The latest generation of DI engines have mostly mitigated the issue of excessive carbon build-up, at least for most drivers. If someone regularly drives their car for only a few miles at a time, before the engine properly heats up, then these drivers may still see some issues. This type of driving is bad for other reasons as well.
 

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A couple questions for our all knowing forum regulars and anybody else that wants to chime in.
Do ANY fuel additives do any good, that is, clean injectors, keep valves clean, keep fuel systems running "better"?
Or is running top tier fuel in the gas tank good enough these days?
If there are any that work, what are they?
I know gasoline is a lot better quality now than when I started driving 50 years ago. Is there cleaning agents in economy gas, even though it's not advertised as such?
Others already suggested, TopTier fuels.

If you have a DI engine that builds up carbon, it is because fuel isn’t there to clean it. All the additives in the world won’t touch it. Most manufacturers have learned and either use a dual port/DI setup or more simply redesigned PCV systems to preclude excess oil in the intake.
 

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I would surmise to say that even 87 gas from most suppliers has some cleaning additives. As for top-tier gasoline, almost all major brands are top-tier, with the exception Sunoco, which was top-tier till recently. See: Top Tier Detergent Gasoline - Wikipedia With respect to fuel injection cleaning, I see that some dealers have it on their list of recommended Subaru maintenance. For the most part, I doubt that they do anything more than add a bottle of Chevron Techron or STP to the fuel tank (?)
 
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