Yep, i personally watched what happened to my old nx1600's motor using Arco, Diamond Shamrock and other cheap fuels in a matter of 10k miles. Nasty buildup on the intake valves and pistons. Then started using only Chevron and the valves and pistons were spotless in a matter of about 5000 miles of using it. Using a bore scope to look down in the cylinders and at the valves. Crazy stuff. Never cheap out on the fuel unless you absolutely have no choice. Pay that extra 3-5 cents per gallon for the better stuff. Its worth it.