normaly i would say not to use the higher grade fuel as he is just thoughing away money.. but it's a 4.2 he already throw away money buying that POS engine
has he blew the head gaskets yet? lol the 3.8/4.2 v6 was one the worst engines for ever made (i would say the 6.0 but that was navistar and not ford) i freaking hate when they come in at work hate them i am lucky i am a diesel tech
if any thing all he is doing is loosing power. the stock 4.2 computers do not comand that much timing and using a higher octane is also a lower volitility fuelt hat has less energy in it. his truck would get better MPG and power with 87 fuel do to it's more volitility and enrgy it has in it
