Joined: Jul 2007
Location: St. Louis
Yes, you will get many opinions on this one. I used to use Penzoil, now I use Valvoline. I had a minivan with 349,000 miles on it, and ran the cheapest oil I could find with no problems, so go figure. Oil is at its worst when it is dirty. If you run down gravel roads or do short trips or lots of stop'n'go, then perhaps a 3,000 mile interval is best. Like '60's Refugee says, the interval when new was 6,000, and if you get 'er on the highway and don't do much of the above, you'll be just fine at that interval.
Remember these cars aren't the super clean computer controlled cars we have now that can go 10,000 miles between oil changes, so keep your car in good tune, and check your plugs/points/carb adjustments often.
As for brand of oil, look for the (I think?) SAE certification. Believe it or not, not all brands have it. I think there is an AutoZone brand (the generic stuff) that is NOT SAE certified. Stay away from anything without it. My good friend is a pertroleum chemist, and he said there really is no appreciable difference between brands for conventional motor oils.
Can't go wrong with the synthetics.
Also, make sure you're using a good quality oil filter. I can usually pick up the Motorcraft FL-1A filters at Wal-Mart a buck or two cheaper than most auto parts places. Avoid the generic filters.
1966 289-2V C-4 Convertible. 2nd owner, resurrected rustbucket. Factory console and power top, conversion to P/B with dual res MC.
1990 GT 25th Anniversary 5.0 AOD Convertible. SOLD