recently my truck has started to make a rattling noise when the rpms climb over 3000. i took it to the dealer and he told me to put 87 in it and it will stop. i was using 91. this is total dealership BS as the noise is even louder. any help or advice would be greatly appreciated.

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2001 2wd Ford Ranger XLT 4.0 SOHC, Fabteck 3 1/2 spindle lift front 2 in blocks rear.

i would first try changing brands of gas.

i use shell. sometimes chevron.

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2001 2wd Ford Ranger XLT 4.0 SOHC, Fabteck 3 1/2 spindle lift front 2 in blocks rear.