they'll get more than 30mpg, mine used to get 37mpg, my dad's gets 38mpg, now my truck gets 41mpg; however, yours being 4x4 and all will have 4.10 gears, you'll be doing pretty good o get 30-35mpg out of it.
Yes ether is hard on a motor, never had to use it on my truck though, I used an electric hair drier, you heard right. I just stuck it in the flexible rubber tube on the intake and let it heat up a little (I did take off the wing nut and washer to releive pressure, so that alot wouldn't go into the valve cover n' stuff)
I say get it! Even if it did have a glow-plug problem, it's still an easy fix, it's about as hard as changing spark plugs, just that you have to take the metal band off all of them.
Good luck with the buy, since you have been tinkerin' with your gasser, maybe he could put bigger exhaust and stuff on it too, you'd be up here (it's not far up though

) with LUVdiesel and me!
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-Old ride-82 Luv diesel 5spd with some upgrades
-Past rides-82 Sierra, 78 Coupe De'Ville, 91 2dr Blazer, 86 RX7, 86 Porsche 944T (rear-ended and totaled)
-Curr. rides- 1970 Ford LTD 4dr, 390 4Bbl, 2nd owner! With a few Extras

00' Civic beater...