You can switch to synthetic at anytime as long as there are no leaks.
Mobil1~Royal Purple~Pennzoil Ultra
Go to "the oil guy" web site and do some research. These three perform 7500+ miles per oil change. Its cheaper in the long run and better protection.
Are those the only three that lasted that long? What about valvoline?
BV heads, P&P lower, windstar upper, comp 218/226, 4.2 bottom end, 3k stall, flow 40's, O/R x-pipe, Pacesetter lt's, Xcal2, 65mm tb, CAI, 8.8 w/ 3.73's, MM LCA's
coming soon: blower cam and intercooled M112
dealer for Ortiz Performance; tunes, cams, etc. PM me!