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Comment by willyt | Hacker News Reader

If this is also true in the EU, which I expect it is, does that mean there's absolutely no difference between supermarket diesel at £1.60/l and BP diesel at £1.80/l apart from a little bit of stuff, extra detergent or whatever, that BP squirt into it as it's pumped? I wonder if there's some kind of submarine marketing company that spends loads of time on car enthusiasts forums trying to plant the idea that there is a difference.

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(In America) there's a huge difference between "Top Tier" (the brand name) detergent gasoline, and a non-detergent gasoline. As in, basically never run non-detergent gasoline in a modern car, because all your injectors were designed with the detergents in mind.

However, 93 isn't better than 87 unless your car specifically asks for it or is turbocharged and has an ECU that can clearly distinguish them and use different programming.

Even my Turbocharged GTI has a map for 87 octane gasoline, and that's what it's fuel economy is rated with. It does however have a different program for higher octane gasoline, as the engine output was rated using 91 octane.

It's just the detergents, but as I understand it the car enthusiasts know that.

Those detergents do work. You don't need to use them all the time, though. You can just use them occasionally and it will breakdown the buildup from the times when you used regular gas.

I am not convinced that gasoline detergents are anything more than marketing nonsense. You know what is already really corrosive? Regular gasoline.

I am curious to what the buildup you are referring to is, fuel injectors maybe? This might make sense on older multi-point fuel injection cars where their max power is like 60 psi, but on modern direct injection engines the fuel rail pressure is so unbelievably high that the sheer pressure would slice through any form of buildup. (My VAG engine for example, idles at ~700 psi and easily reaches twice that when moderate acceleration is demanded)

If you're in a place with ethanol in the gas as an octane booster you're done right there.

Ethanol is fantastic at removing deposits. So much so when it was phased in 20 years tons of engines that had been running on non-ethanol blends had tons of trouble with deposits breaking loose and causing issues, especially anything with a carburetor that had built up deposits. The Ethanol broke down the deposits and then they'd get lodged in jets.

Modern engines seem way better at not building up deposits like you said, but things like Direct Injection also didn't become common (at least in the US) till Ethanol was also present.

The issue is not corrosion but buildup, which detergents help to disperse. High pressure itself doesn't cause high sheer forces during fluid flow, rather high velocity does. Any regions of the system with low velocity w.r.t. the surface could still experience buildups. Whether that happens in practice is certainly debated.

As a practical matter, it doesn't make a difference because almost everyone occasionally uses detergent gasoline (e.g., when that is the most convenient gas station).

> High pressure itself doesn't cause high sheer forces during fluid flow, rather high velocity does

I am definitely not someone with experience in fluid mechanics, but I feel this goes against a layman's understanding of it? Could you provide some quick material on this claim so I could understand it? I already tried searching it but due to my limited knowledge of the subject I couldn't word my search to get the results I wanted.

I thought all gasoline had some detergents in it, not just the name brand stuff? I understood it as the name brand places add extra detergents or fancier additives, according to their marketing at least.

What do you mean by "regular gasoline"? Are you referring to the different octane levels?

That wasn't clear - I just meant gas that's not top-tier detergent gas.

is it the same stuff as the good ole Wynn's that my dad used to put on the car?

Same or similar

By and large, they're pretty much the same. However:

- Detergent mix might be different

- the quality control of your super market might not equal the brand name pump (ie test the tanks for water, dirt, contaminants, etc).

However, I'd be more concerned routinely getting Ex gas from the same middle-of-nowhere gas station that gets little traffic than suburban supermarket gas. Once in a while while you have 1000 mi to go on a trip, that gas wont affect anything. But, sitting in your half filled tank everyday that ethanol will suck up moisture and even polymerize into gunk.

The marketing company would be Top Tier Gasoline https://www.toptiergas.com/ . You can see their ram symbol on pumps.

At least in Switzerland for example a lot of the Miniprix, BP[1] and Shell gas stations have all the same gas as it comes via the same supplier which is Oel-Pool AG and its subsidiaries. Oel Pool is also selling their surplus gas via their own low cost gas station networks which has the symbol of an elephant trunk.

[1] https://www.oel-pool.com/info-center/neuigkeiten/detail/uebe...

You can also buy additives occasionally to clean your injectors. I don't know how well they work but they did seem to work for me.

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