Should I pay extra for Shell gasoline?
July 28, 2010 12:02 AM   Subscribe

How much to gasoline detergents matter?

I recently bought my first car that isn't a beater (2007 Toyota Yaris). Being as excited as I am about this, I want to take great care of it. Most people seem to agree that Shell and Chevron have the best additives. Unfortunately, the closest Shell to my house is about 10 cents more expensive than the closest Marathon. Do Shell's (or anyone's) detergents really make that much of a difference? Is there anything to the label "top tier" gasoline (which Shell is but Marathon is not), or is it just a sales angle?
posted by Roman Graves to Travel & Transportation (13 answers total) 1 user marked this as a favorite
Via Car Talk myths:

"Premium has special or extra detergents in it that are worth the added cost."

It's true that premium gas does contain special or extra detergents, but in our opinion they're of no additional benefit.

Our advice is to ignore any sales pitch about the super-special detergents that come in the premium-grade fuel.

These days, all of the gasoline from the major gas companies contain more than enough detergents to keep your engine clean. Period.

The only reason you might have a use for the extra detergents in premium, is if you have a noticeably dirty engine, and need to scrub carbon and other crud off engine components. (And, if you're doing that, we'd instead suggest that you toss in one of the many fine engine additives.)

You said "major gas companies." Is there a difference in the gas between the big names, and the El-Cheapo gasoline at my local Costco or Stupey-Mart?

There is. A number of years ago, some of the major auto manufacturers were ticked off with the deposits from gas that met EPA detergent standards. In other words, they were afraid they'd take the heat for problems, when their customer's engines clogged up from the twigs and dirt that was getting deposited on their fine handiwork.

So, they set their own guidelines, which they call "Tier 2." All of the gas from the major gas companies meets the Tier 2 standards. The gas at your local Quickie Mart probably does not. The difference? In some tests, after about 10,000 miles, there was a minor amount of crud built up on engine components that ran exclusively on Quickie-Mart gas. Do we think this is an issue? Not really. But, would we advise running your car for 100,000 miles only on Quickie-Mart gas? Not if you're concerned about the longevity of your vehicle. We recommend switching back and forth between Tier 1 and Tier 2 — maybe every other tank full — to keep your engine running clean.

posted by Blazecock Pileon at 12:19 AM on July 28, 2010 [1 favorite]

Car talk explains the Top Tier thing. Personally I think it's irrational to spend 10 extra cents per gallon just to get a little extra detergent when you can pop a $3 can of injector cleaner in the tank every 10k or 20k miles and get the same effect.
posted by Rhomboid at 12:21 AM on July 28, 2010 [1 favorite]

Well that solves it. Should have known - go to Car Talk.
posted by Roman Graves at 12:35 AM on July 28, 2010

I'm probably the odd one out here. I fill up solely with Shell 93, but there are plenty of Shell stations around and they're not much more expensive than other places (if at all).

My car's engine is somewhat notorious for problems with engine buildup, so I'm not taking any chances. (There have been reports of dealers not paying for repairs because they blamed it on 'bad gas'. They probably can't do this, but again, I don't want to have to fight that fight. But I digress..).

That said, if I were in your shoes, I'd probably do the thing mentioned in the above quote regarding switching between tiers now and then. Just make sure to stick to the same octane.

As a side note, it looks like Exxon and Mobil are now on the Top Tier list (they weren't when the Car Talk article linked above was published). Interesting.
posted by Tu13es at 5:40 AM on July 28, 2010

I track my mileage carefully and drive a lot (~100 miles/day). The cleaner the engine is, the better mileage I get. The biggest difference so far has been due to Techron, which Chevron puts in it's fuel (you have to get the right one though), that the Texaco near my old house had. After moving the mileage dropped off, and I eventually figured it out and started putting it back in manually.

Every fill up, I dump a bit of Techron in before the gas. I stick with Tier 2 gas but I'll bet you could do the every-other fill up suggested above and keep that engine clean if you do the same thing I do with Techron.

Why Techron? Ask the big three. There's more on that site.

163,000 miles, 33mpg, 2004 Corolla. Restore seems to be worth another 2-3 mpg after 80,000 miles or so, and for stuck piston rings I use an engine flush every 50,000 or so. The engine starts burning oil so it's easy to tell when it's needed.
posted by jwells at 5:58 AM on July 28, 2010

I doubt it makes much of a difference from Kwik-E-Mart to BP or Shell. If you're concerned about carbon build up run a 1/2 can of Seafoam through the gas tank every time you change the oil. That will take care of any build up on the injectors. Personally, I only run 91 or 93 in my Impreza WRX, but the nature of Forced Induction makes that absolutely necessary. For a naturally aspirated engine (or any engine for that matter), stick with what the manual says. I'm guessing it says 87. You're going to get the best gas mileage and it's the cheapest gas you can get. If you'd like to save <$2.00 per fill, fill up at the cheap stations, it's not that big of a deal. There aren't that many refineries in the US, hence why a lot of those little stations are supplied by BP, Shell, Mobile, etc.
posted by ganzhimself at 7:19 AM on July 28, 2010 [1 favorite]

Anecdote: I had a friend who believed that Shell gas was the best gas and he was willing to pay more for it and use it exclusively. His engine needed some work; he took it to the Shell station mechanic who told him the trouble was probably due to the bad gas that he was putting in his tank and he should be buying Shell gas.
posted by CathyG at 8:00 AM on July 28, 2010 [1 favorite]

No it's not worth it. Your Toyota will be optimized to run on standard petrol rather than premium petrol, since that's what Toyota would expect you to run it on. It's not a high performance engine that might garner a performance benefit benefit from the higher octane of premium petrol. The only point I'd make is buy from a reputable brand, and not always from the discount station or supermarket station all the time.
My Honda dealer told me not to worry about premium petrol and said that the car was designed to run on standard.
posted by arcticseal at 9:52 AM on July 28, 2010

There's a larger point here: "Most people seem to agree ..."

Most people don't know squat about cars and, where things like the chemistry and physics of combustion are concerned, that often includes mechanics. People who rail against alternative medicine often engage in exactly the same kind of woo with their cars.

"I use Chevron gas and I've never thrown a rod, so it must work!"

If you want to know how to take care of your car, don't ask your friends what works unless they're Jon-o or Brockles, or an automotive engineer.

Sorry, it's just a pet peeve of mine.
posted by klanawa at 10:44 AM on July 28, 2010

Both of my Subarus - one NA, one turbo - perform better after I fill up at a Chevron and continue to perform that way for a couple weeks, even after a fill-up at a Shell. I suspect there is something to Techron. Given prices are pretty much consistent across brands here (SF bay area), I fill up at Chevron stations preferentially.
posted by jet_silver at 12:58 PM on July 28, 2010

Do not confuse octane requirements with detergency. Two completely different things.

Use whatever grade of gas the car calls for, either in the manual or by performance. Some cars only require 87 but can take advantage of 91 or 93. Others won't care. And some others will actually run worse on higher octane.

I can't prove it, but I read somewhere that most stations use the same detergent in all grades. Or maybe that was a requirement of a "tier 2" gasoline?

One thing to consider is not picking a single gasoline brand and sticking with it, but switching up among a couple of favorites. Each detergent chemistry will loosen different things, and switching them up theoretically gets more out.

Finally, it is *MUCH* easier to keep dirt from sticking in the first place than it is to clean it out after it has accumulated. But it is not as spectacular as buying a bottle of magic fluid and "restoring" the power and smoothness you hadn't noticed you lost. Better to never lose it in the first place.

(You car probably fills up at about 10 or 11 gallons, right? 10 cents more a gallon is the difference between a 28.99 fillup and a 29.99 fillup. Add those dollars up and you pretty much get to the same price as buying cheaper gas and a bottle of expensive cleaner used once an oil change. I just buy the good gas so I'm done with it.)
posted by gjc at 6:06 PM on July 28, 2010

It also depends on how your gas is introduced into the cylinder - direct fuel injection systems don't blow gasoline over your valves, so they don't receive any benefit from the additives. Apparently you have to Seafoam those engines every couple-thousand miles if you want to clean your valves.
posted by Kyol at 10:33 PM on July 28, 2010

Excellents points everyone, but I think gjc is right. It only turns out to be a couple dollars difference between cleaning the engine and keeping it clean all the time.
posted by Roman Graves at 9:21 PM on July 29, 2010

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