Costco 93 premium
Intermediate
Joined: Jun 2023
Posts: 430
Likes: 400
From: FL
The only practical difference between different gasoline brands of the same octane from a chemical perspective is the additive package in it. More expensive brands theoretically have more expensive (read: better) additives. Do those additives really matter? I think when Direct Injection first hit the scene and there was a rash of engine failures caused by dirty valve heads, maybe, but our engines are direct and port injected, the port injection keeps the valves clean, in that respect quality will matter less.
In theory, a more expensive brand also has a better maintained station, and that matters more. Better moisture control and cleanliness in the tanks and lines. I've been to a couple Marathon stations that looked so bad that I thought there was no way they were actually maintaining the systems well. But I've been to some Exxons that looked like crap too.
I'd expect all the bulk store gas brands (Costco, Sams, BJs, Walmart) to operate well-maintained stations with midrange additive packages. Will you notice a difference between that and Mobil? Doubt it.
A Speedway or Valero station that looks well-taken care of will probably feed your car cleaner fuel with less moisture content than a Shell that looks like its from the set of Escape from New York.
In theory, a more expensive brand also has a better maintained station, and that matters more. Better moisture control and cleanliness in the tanks and lines. I've been to a couple Marathon stations that looked so bad that I thought there was no way they were actually maintaining the systems well. But I've been to some Exxons that looked like crap too.
I'd expect all the bulk store gas brands (Costco, Sams, BJs, Walmart) to operate well-maintained stations with midrange additive packages. Will you notice a difference between that and Mobil? Doubt it.
A Speedway or Valero station that looks well-taken care of will probably feed your car cleaner fuel with less moisture content than a Shell that looks like its from the set of Escape from New York.
Intermediate
Joined: Oct 2023
Posts: 255
Likes: 60
From: Texas
Driver
Joined: Aug 2015
Posts: 70
Likes: 22
From: Florida (Miami)
I get gas anywhere I can. I agree that Shell and Exxon are both solid choices though. Just make sure to do 91+ and you should be fine. I also feel that some Shell or Exxon gas stations are better than others.
10th Gear
Joined: Mar 2026
Posts: 17
Likes: 3
From: PA
After a year or so of pumping Shell V-Power, I decided to try out Costco premium since I got their membership recently. Since early on, I noticed my engine starts take like 1.5 or 2 cranks, basically a slight delay that I didn't expect a new car to have. Nothing serious, just something I noticed but wasn't sure if normal or not being a first time new car owner. I've been pumping Shell exclusively (usually the same station) even on previous cars and never had any issues related to fuel that I'm aware of. It did make me ponder though about battery or starter possibly not being 100% healthy.
After pumping 14gals of Costco 93 though with ~10miles on the tank and sitting over the weekend, yesterday morning startup was noticably faster and smoother, like just 1 crank with no hesitation. Does this mean the Costco gas is cleaner or better? Anyone else experienced this before when switching fuel brands or am I just imagining things?
Also, on a somewhat related topic. Do I need to worry about fuel pump priming if I don't lock the car overnight or the weekend? I read something about the fuel being primed when the car is unlocked but I don't lock when garaged.
Thanks in advanced for any response.
After pumping 14gals of Costco 93 though with ~10miles on the tank and sitting over the weekend, yesterday morning startup was noticably faster and smoother, like just 1 crank with no hesitation. Does this mean the Costco gas is cleaner or better? Anyone else experienced this before when switching fuel brands or am I just imagining things?
Also, on a somewhat related topic. Do I need to worry about fuel pump priming if I don't lock the car overnight or the weekend? I read something about the fuel being primed when the car is unlocked but I don't lock when garaged.
Thanks in advanced for any response.
I recently learned that Costco buys standard untreated gas and adds their additives on site at the pumps, it helps keep their costs down. I ran strictly 94 from Sunoco, I even got it from the same pump every time I went, the only time I noticed a crank difference was temp related, we had a few weeks here in the NE that were frigid. I also wouldn’t worry about the priming, you could lock and unlock the car for peace of mind. This car (minus a few minor issues) will outlast everything else on the road in my opinion. Best of luck!
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