Maintenance to regain performance?

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costco gas is about as good as putting cow feces in your tank.

I would love to see the proof behind this statement. Costco gas has been working just fine in my car since I bought it, it works fine in my friend's Sti, and worked fine in my old mazdaspeed3.

I would love to see the proof behind this statement. Costco gas has been working just fine in my car since I bought it, it works fine in my friend's Sti, and worked fine in my old mazdaspeed3.

The supplier of costco gas is garbage, it may work fine for you, but I certainly wouldn't put it in my car. Consistency is key. You'd be surprised what kind of logs I've done when people go to "lowest price" gas stations.

I use the same stations, and monitor their fuel performance through fuel economy.

7-11 has treated me well, and of course Exxon/Shell/Gulf have been consistently good.

What you need to keep in mind is that fuel is a matter of location. 3 stations next to each other all likely get their base fuel from the same storage facilities. The governing stations then implement their detergent packages at a processing plant before trucking fuel to stations. So Shell gas might have been refined by BP. It's all a commodity trade. It works, because there are almost no variations in refinery products. Standards are forced to be met.

If you find a brand you like, their fuel is likely to be approximately consistent across the nation. Gulf 93 in MD will almost assuredly be identical to Gulf 93 in Florida.

Another consideration is location based detergents. Colorado fuel might not have the same detergent package as Maryland fuel.

This is all something to consider when you get your car tuned. A conservative tune is going to be more capable of handling the inevitable variations in fuel quality and content.

I would love to see the proof behind this statement. Costco gas has been working just fine in my car since I bought it, it works fine in my friend's Sti, and worked fine in my old mazdaspeed3.

I'll grab a shovel and my AP and hit up the neighbor and let you know how it works out. Maybe there's an ots cow-patty map from Cobb somewhere and then after I run the "sh!t" out of it, stop at costco and log some more.

Judging your gas by fuel economy is about as accurate as judging the nutrition value of your food by your underwear streaks. While eating a spinach salad and Burger King may produce similar results the spinach salad probably did less damage than a California Whopper from the creepy King.

Since you just bought this car at 70k, my rule of thumb on any used car is to redo the last major service since it very likely was not completed.

For your car that would be:

Oil change

Brake flush

Coolant flush

Trans and Duffy fluid flush

Plugs

In particular, I would also do a compression test and switch to synthetic fluids. We like Amsoil in the trans and diffys and redline, amsoil or motul in the engine.

NGK oem plugs are also suggested.

Mike