Costco gas

[cz5gt]

In my area costco is ok gas to get you from A to B. Shell and Chevron are better but cost more.
Source : obdii monitoring and personal feel for the cars.

 

[GTXT23]

In my area costco is ok gas to get you from A to B. Shell and Chevron are better but cost more.
Source : obdii monitoring and personal feel for the cars.

Those are my top 2 as well -- prices have come down - and I stay consistent on the brand and refill locations knowing when they changed the underground tanks last--were under $3.50/gal-for 91 now so Costco dosent beat that by much at least here - Texaco comes in #1 which is Chevron......however on my 2.5 2010 Mazda NA MZR engine -- it does well on anything so I use Costco for that guy ---but the high compression CX5 gets temperamental if I start swapping brands and octane-

 

[ruthrj]

My ‘23 hasn’t had a single tank of non Top Tier fuel. I ran Costcos higher octane for my ‘23s first 3k miles. I then ran Marathon 87 octane almost exclusively for the last 17k miles with the occasional tank of Chevron 87 octane. Marathon has a great free rewards program that my wife and I both use under my phone number. It’s nearly the cheapest top tier fuel around and is often cheaper than “cheap” gas stations when coupled with rewards. Costco is usually cheaper by 5-10 cents but obviously requires a membership (which I’ll probably keep for their good Michelin tire prices coupled with warranty benefits).

I’m currently doing a few tanks of Costco higher octane for grins and giggles. I’ll do three tanks of that before I make a final call, but I can’t shake my initial feelings purely off the butt dyno 1) No perceptible difference between these top tier fuels with 87 or 93 octane, and 2) it is REALLY difficult to go above 4k rpms for the higher octane HP and torque benefit even with a dally small mountain climb.

I might switch to Costco 87 moving forward based on the supposed DI additive package benefit, or stick with Marathon 87. Both are Top Tier and choosing that puts you ahead IMO for fuel injectors alone.

 

[N7turbo]

In my area costco is ok gas to get you from A to B. Shell and Chevron are better but cost more.
Source : obdii monitoring and personal feel for the cars.

Ever run Philips 66? That's our primary station here with 91, and my car always runs really well with it.

 

[theblooms]

Costco is "top tier" gas that I've used almost exclusively for 20 years or so with nary a problem!

Wow, you're right! I didn't realize that!

 

[cz5gt]

Ever run Philips 66? That's our primary station here with 91, and my car always runs really well with it.

Unfortunately dont have that. Only shell chevron costco and the smaller franchises like quicktrip and circle k. Wish we had 93 but sadly only 91.

 

[N7turbo]

We have only one station in town with 93, and unfortunately it is not a top-tier station.

 

[ruthrj]

My personal verdict: I can’t tell a difference in day to day driving between Costco 87 and 93 octane with my 2.5T. You really have to give this car the beans and be in sport mode to try to keep it from shifting prior to 4k rpm’s. I’ll save the 50 cents a gallon and stick with 87.

Changing my route to work has really helped my gas mileage though. Went from 25-26 mpg to 27-28, no different with respect to octane.

 

[cz5gt]

driving steady rpm and steady slow acceleration one could probably drive on 85 if there was any.
Sudden heavy acceleration from low rpms and lower speed is where it matters how and what fuel is used. i.e or when the engine is at its highest load. This is usually where knock and lspi happens and ignition has to be top notch.

 

[N7turbo]

driving steady rpm and steady slow acceleration one could probably drive on 85 if there was any.

At high altitude there is

 

[ruthrj]

driving steady rpm and steady slow acceleration one could probably drive on 85 if there was any.
Sudden heavy acceleration from low rpms and lower speed is where it matters how and what fuel is used. i.e or when the engine is at its highest load. This is usually where knock and lspi happens and ignition has to be top notch.

I have pretty cool route options where I live (TN valley). Lots of hills, rural backroads, and my home is on a small mountain with couple hairpin turns. I was hoping to notice some sort of difference with 87 vs 93 with “spirited” mountain driving but man, I just don’t. That’s not disappointing though, it’s amazing what Mazda was able to pull off with this design. I’ve never found the performance to be lacking!

The route change on my work commute was skipping a small mountain pass. Bought me another 10 miles per tank of gas lol

 

[jadmt]

At high altitude there is

in Montana it is somewhere around elevation 4500' or so gets 85 for regular..you see it quite often.

 

[GTXT23]

The Octane debate continues --- I do notice a huge difference in my 25 NA with 91- live at 5500 ft - not just power but it just runs smoother at idle and in gear transitions- Brand-Texaco/Chev - Top Tier - - The kicker is why on the Turbo is there a measurable difference in HP with higher octane fuel - per Mazda ? As well the owners manual states that when towing with NA or T - Use high octane fuel - ? just saying - Additionally Higher Octane fuel is in general mandatory on performance higher compression engines - due to the potential for premature detonation on lower octane fuels in a HC engine - Heres some scientific info on this sunject

 

[N7turbo]

in Montana it is somewhere around elevation 4500' or so gets 85 for regular..you see it quite often.

And Colorado.

 

[a69mach1377]

And NM also in some places...

 

[SBMongoos]

Been using Costco 85 octane for years and been happy. Get good mpg on my 16.5' GT. Usually it's at least 15 cents cheaper but often even more than that compared to others. Currently it's at least 60 cents less per gallon or more than other local gas stations. I'm in CO.