m.p.g and lead additive

Lead additive is basically a scam -- what lead used to do was lubricate the valve seats on the older vehicles. With the advent of unleaded gasoline, hardened valve seats came into use and eliminated the need for lead in fuel. I used to use lead additive in my '68 Caddy...Saw no real benefit from doing it, except I was spending $2 extra to put a bottle into each tank of gas. If your '73 has "Unleaded fuel only" on it, either on the fuel cap, etc., you are fine without any additive. As far as I have read, no one has had a massive problem with using unleaded fuel without additive in older vehicles, and I've been involved with older cars for quite a few years. As far as your MPG, I'd imagine 15-20 tops, on the highway.

my high milage 73 super beetle gets 27-29mpg on 87 octane on the highway running 60-75mph.

I get around 27 mpg in my 74 Super Beetle with 22,000 original actual mile engine, and this is in stop and go traffic for the most part of my commute daily. I run Sea Foam every other tank to keep the carbon off of the valves, Besides that, I do run 87 Octane full gasoline with no ethanol. Still runs like new. Good luck guys....