Blogs Car Info Our Show Deals Mechanics Files Vehicle Donation

Gasoline question

So we just bought a new Hyundai and I’m supposed to use top tier gas. Done some research on it and I have very limited options regarding availability.
2 stations in town carry it according to their corporate websites. There’s supposed to be a label of the logo on the pump.
Well I haven’t found any labels and both stations use the same company to fill their tanks. It’s the same company that hauls fuel to nearly every station in the area.
So, how can I be sure I’m getting the right gas?
Hyundai seems pretty serious about using it.

If the brand says they’re top tier, then I’d just believe them and use it. Not like you have much of a choice. And yes, the same truck may deliver gas to multiple stations, but they probably fill up between changing brands, if the specs are different.


I wouldn’t lose any sleep over this. It’s very uncommon to have any fuel related issues, and in the rare case that you might, the fuel company will be on the hook for repairs if they sell you bad gas.

I figured it was to try to avoid valve deposits on the direct injection engines.

I suppose it’s possible, but gunking up the valves on DI engines occurs mostly in the intake air path, and in DI engines there’s no gasoline flowing through that area, so it wouldn’t matter what brand of gas you used. I’d guess the reason for recommending “top tier” is more related to the fuel system, and in particular the direct injector system. Here’s a pretty good summary.


From what I’ve read the theory is cleaner burning gas equals fewer deposits on the valves. Could be bad science or good marketing to sell higher priced gas.
I wasn’t crazy about a GDI engine but it seemed like the cars we liked either had that or a CVT transmission. I wasn’t crazy about those either.

Costco fuel is top tier rated

As I understand it, that is the crux of the problem. All engines have valve overlap and just by nature of engine operation the valve backsides are exposed to combustion byproducts. The exhaust valves get hotter and burn off deposits. The intake valves get coked up. In wet injection, the incoming fuel wets the backside of the valve and cleans off the deposits. In DI, the valve is dry and the deposits accumulate. Using the cleanest burning gas and best additive package for these engines reduces need for expensive valve cleaning operations. That’s the reasoning from what I’ve read about it…

DI engines also get clogged up because of crankcase blowby gasses being recirculated through for burning (EGR). The deposits condense on the intake and exhaust valves and build up to clog the flow. Cars with oil use problems have quite a lot of problems with this. Then there is a lack of fuel coming through and washing it away. Cleaning products introduced into the intake from Seafoam, CRC, BG and others are introduced to clean them away before they get too bad. When they get really bad, walnut shells need to be blasted into the intake, or manual scraping is done to clean away deposits.


At least one manufacturer, (maybe more), has a dual-pulse direct injection. It has a minor initial spray of fuel while the intake valve is closing, but still partially open. That enables fuel to get sprayed on the back side of the valve to help wash it off.


Ask your Hyundai dealer where they gas up their Hyundais.

1 Like

All gas in the US has to meet a minimum amount of additives and tier one just has some extra additives. I am in the minority here but all I do is avoid places with low sales volume .

Toyota and Ford, to name 2, have engines with 2 sets of injectors, one direct and the other port injection. The port injection washes the intake valves and the direct allows all the goodness from these systems - cooling the intake charge so higher compression can be used, timing the fuel injection to control lean-burn or build more hp.


Are these stations also in this list?

Although I have no personal knowledge of this, I think I’ve read here that different brands often use the same gas with different additives added at delivery time, so it’s probably not a concern that the same delivery company is used.

Luckily for me, the one Top Tier brand here in town also happens to be consistently one of the cheapest stations, so I really don’t have to debate whether to use it or not. They do have the label on the pump, for what that’s worth.

1 Like

Turns out in of the new guys where I work used to be a fuel hauler. I asked him if all gas is the same since the same truck visits different stations.
Basically the gas is the same. But the additives they put in at each station varies. So the different “recipe” is what makes one better or worse.
I asked if they really take it seriously and he said yes. Random testing by the customer keeps them honest.
So I guess I got my answer. Maybe this helps others too.

1 Like

Do a search on Top Tier. A number of manufacturers feel their engines require fuel with more than the govt. mandated minimum detergent additives. AAA published a report with results of testing that indicated significantly reduced intake valve deposits with Top Tier gas:

Quite a number of brands are Top Tier now, including Costco.

Hyundai (in my Tucson manual at least) says if top tier fuel is not available then pour a bottle of fuel injector cleaner in the gas tank at each oil change.
The concern is to clean the fuel injectors, since their tips are in the combustion chamber and prone to combustion byproduct deposits.
The valves are a separate issue.


Ok, that makes sense.

See the brands on this link:

1 Like

I do like to see the TopTier sticker on the pump. The Sunoco near me does not display the sticker. Neither TopTier nor Sunoco would confirm accreditation.