I posted this before and received some pushback. Some gasolines are certified as Top Tier because of their additive package. Many car makers, including Honda, recommend Top Tier gas. I always use it. Good video below.

 

I've used it since I bought my 2018. I'm fortunate to have 2 gas stations on my street corner, one top tier one not, both always at the same price. People argue that regular gas already contain additive cleaners as mandated by government and that's true, but as shown in the video top tier contains substantially more additives which significantly improves keeping the engine (especially things like fuel injectors) clean. Sure, there are many things which can go wrong with my car, but there are more things that can go wrong with cars owned by people who rush to buy gas from the absolute cheapest gas stations around.

 

Ok, you got me.

 

I have been using the cheapest regular 87 octane gas on my 2017 Honda Fit LX CVT since day it was new without any issues.On open highways, I have consistently average over 40 mpg. I am so confident that I don't even check the oil level between oil/filter change at 20% indicator, that amounts of over 9K miles driven. The current ODO reads 159K miles. The Fit has been a great little economy car that has a large cargo space compared to other cars its size.

 

I always use top tier in everything and is especially important to keep the injectors clean in a direct injection engine. Good news, they are coming up with Top Tier + which can help with IVD (intake Valve Deposit).

Source, artificial intelligence:

​​​​​​Top Tier+ gasoline is an enhanced standard within the TOP TIER program, designed to improve engine cleanliness and performance, particularly in newer GDI (Gasoline Direct Injection) engines. It includes a GDI fuel injector cleanliness test and monitors emissions and combustion behavior.

 

On a slightly related note (longer engine life), the new engine oil standard GF-7 has been released and should soon be on the shelves replacing all the GF-6 oils we have been using over the last few years. Seems oriented towards better fuel economy, reducing timing chain wear, etc.

New oil standard

 

I might be missing something, but it's unclear to me how fuel detergents (or higher levels of detergents in Top Tier fuel) will reduce carbon deposits on valves in a direct-injection engine. Isn't the whole point of DI that the fuel is more efficiently burned because it is shot straight into the combustion chamber? Do the detergents survive the combustion process to clean the valves when they open? Even if that were the case, wouldn't those detergents exit past the exhaust valves before the intake valves opened? And even if some detergents persisted in the combustion chamber after the exhaust valves opened and closed, how would they fight upstream against the incoming air when the intake valves opened so as to clean the top of the valves?

In contrast, my 2010 Fit Sport has sequential multi-port fuel injection, which I have always understood to mean the fuel is injected above/before the intake valves, in which case detergents would directly interact with those valves as the fuel-air mixture enters the combustion chamber. Similar to above, I'm not sure that detergents in the fuel would survive the combustion process to interact with the exhaust valves when they open.

Having said that, I have been using Sta-Bil 360 Performance in my Fit (and snowblower) for several years. The packaging indicates that it contains the same PEA (polyetheramine) talked about in the video above, but I mostly use it because of:
1) concerns with ethanol in the fuel available to me locally and
2) my Fit often sits for weeks or even months at a time between drives so I like to use a fuel stabilizer (especially in winter); we have a Nissan Leaf EV that we use for almost all local driving whereas the Fit is reserved for long trips.

I checked out the Top Tier station locator website referenced in the video above and learned that the conveniently located gas station that opened in my nearest town last year is not listed, so many of my fill-ups are apparently non-Top Tier fuel. If we ignore the fact that I already use Sta-Bil fuel additive in every tank, I am curious regarding the video's recommendation to use the expensive Techron additive once per 3000 miles if you can't get Top Tier fuel. For my Fit with a 10.6 gallon tank and 38.4 mpg lifetime efficiency, that would mean that my fuel system would see cleaning for approximately 400 out of every 3000 miles of driving. I guess that's better than nothing, but why would I prefer that over a product that goes in every tank of fuel at a lower cost? The video says the bottle of Techron costs about $1/gallon of fuel, which as noted above would give me approximately 400 miles of "cleaning." The Sta-Bil I use costs $0.11-$0.12/gallon of fuel and one bottle lasts me for approximately 6000 miles of driving. Both products contain the magical PEA referenced in the Youtube video.

Although my local gas station apparently sucks, the Top Tier website showed me a small number of locations in nearby towns that do sell Top Tier fuel. As I happened to be driving the Fit yesterday on a 140-mile roundtrip to drop my wife at the airport I made a point to visit one of these stations, where despite a diligent search of all eight pumps I could find no indication that Top Tier fuel was available. Since I had already stopped I fueled up with their mystery gas, used my standard Sta-Bil 360 Performance, and called it good.

 

I find that a lot of stations that supposedly offer Top Tier gasoline do not advertise that fact on the pumps.

Interestingly, around here (urban Minnesota), the chains with the most stations in the area are not Top Tier participants, so finding TT gasoline usually means finding the national brands that are kind of off the beaten path. Sometimes I wonder if I'm trading the (supposed) TT label for gas that isn't as fresh. But there's no way of knowing any of it so I just fill up (unless the place is super sketchy) and keep the receipt.

 

"I might be missing something, but it's unclear to me how fuel detergents (or higher levels of detergents in Top Tier fuel) will reduce carbon deposits on valves in a direct-injection engine" Ask Honda. It's their idea.

 

@Drew21 "I might be missing something, but it's unclear to me how fuel detergents (or higher levels of detergents in Top Tier fuel) will reduce carbon deposits on valves in a direct-injection engine."

I'm with Drew. In D.I. engines, fuel does not pass through the intake valves. Toyota came up with an injection system on the FR-S/GR86 that piggybacks port injection on top of direct injection just to keep the valves clean.

I bought my '13 Fit for the port injection. Not just because the Fit is a babe magnet.

 

I don't know Honda or how to contact them. Since you started the thread (and noted that you have posted the Youtube video previously), I am hopeful that you might have some useful contributions or hypotheses.

I spent about 30 minutes visiting multiple websites that sing the praises of Top Tier fuel and fuel additives in general.

They each said something similar to the following quote: "Direct injection engines pose unique challenges as deposits can accumulate on the intake valves due to the absence of fuel spraying over them. Detergent gas additives designed for direct injection engines focus on cleaning the intake valves, maintaining their cleanliness, and preventing the formation of carbon deposits."

This directly supports my hypothesis that fuel additives can have benefits when the fuel is added upstream of the intake valves, but none of the websites I visited (which again, were all pro-fuel additive for DI engines) offered any explanation for how fuel additives could access the top of the intake valve in a DI engine.

I did learn more about the common detergent chemicals in fuel additives, including (to answer one of my questions) the fact that PEA is stable through the combustion process.

"Three nitrogen-based detergents are often found in gasoline and fuel additives as they’re effective at scrubbing away carbon.

• Polyisobutylene (PIB), commonly found in gasoline and fuel additives, can prevent carbon from forming, helping keep a clean engine clean. However, it won’t really remove existing deposits.
• Polyisobuteneamine (PIBA), also often found in fuel and additives, can actually remove some deposits. It can’t survive the temperatures of the combustion chamber, though, so think of it as limited to the injectors, intake valves and intake ports.
• Polyetheramine (PEA), more commonly found in fuel additives and specialty race fuels, remains stable in the heat of the combustion chamber, allowing it to do more cleaning."

As above, I still question how these chemicals can effectively target deposits on the top of the intake valve, as shown and implied in the Youtube video in the first post, in a DI engine when the fuel by definition isn't interacting with the top of the valves.

Next thing you know Dawn will be telling me to squirt their dish soap directly into my septic tank when I'm preparing to wash the dishes.

 

They're already suggesting a quick squeeze around the bottom of your washing machine tub for use as a laundry degreaser.

 

While cleaning up from my "research," I had one open website I hadn't looked at, which states that:

"Shell, Chevron, Mobil and the other refiners blend gasoline with high detergent levels to clean the fuel injectors and intake valves. The detergents are formulated to inhibit and remove carbon deposits. This works on engines with port injection, but not with direct injection.

So what makes the difference? Port injection engines have fuel injectors that spray gasoline right onto the intake valves. Using high detergent Top Tier gasoline in a port injection engine can clean the intake valves reducing carbon deposits.

Direct injection engines spray the fuel directly into the combustion chambers. Since the fuel is no longer being sprayed on the intake valves, the detergents in the gasoline don’t get a chance to clean the valves, causing excessive carbon buildup."