Fuel grades for vehicles

I drive a 2003 Chevy Silverado 2500 HD Crew Cab Vortec 6000 that states to use fuel grade 87 or higher. I recently talked to an owner of the same truck, a newer year, who was told that using 87 in Colorado is a waste of money because of the altitude effect on the ignition of the fuel. Is there any validity to that opinion, and does that mean you need to use a higher grade as you travel in lower altitudes? I am getting ready to travel from CO to CT, and am interested in getting the best mileage possible with my gas guzzler. Thanks for any helpful info you have!

At higher altitudes you can use a lower octane fuel. But when you come back to sea-level the lower octane may cause the engine to knock.

As for 87 octane…that’s the LOWEST I’m able to buy here in NH.

Agree; if the manual states that octane required is 87 or higher, that means the car will run fine on REGULAR gas, anywhere in the US. Owners manual are written for the whole conuntry, including Alaska and Hawaii. There might be some very low octane gas somewhere in Mexico, hence the instructions.

You want to look for “regular” rather than a specific octane. At lower elevations, that’s 87, but at high elevations (such as Denver and up), 85 is sufficient to prevent knocking. This may not apply to turbo and supercharged engines. As mentioned above, 87 octane regular would apply to most of the country, so that’s what’s written in the owner’s manual.