86 GMC 2wd 3spd 350: So after new heads, plugs & wires, I consisently get 12 mpg

[lbrowne]

Is that a little low? I have 3.73 gears, truck has 119k miles.

My daily commute, and yes I drive it daily since I'm inbetween cars right now, it's partial highway but can get congested and then suburban neighborhood drive home. but not a huge lot of stop n go traffic. On the highway it can slow to about 35-40, then get back up to 60 again.

On the highway I do about 60-65, all other times it's about 35-45. I've eliminated my heavier foot, and I consistently get 12.xx mpg. (over the last 8 tanks since I started monitoring it)

I'm going to check the timing soon as I can get my hands on a timing light (I can't understand how I don't have one yet lol)

Earlier the summer we installed a set of professionally rebuilt heads (stock spec, no more blue smoke yay), she has new plugs and wires, good air filter.

I'm thinking maybe a vacuum leak too? That would affect gas mileage wouldn't it?

[Captkaos]

For the specs you provided, 12.x is respectable, What size tires?  Is the speedo/odo accurate?

[lbrowne]

You know what, I was just coming back to post that I'm running 31x10.50 tires. I know those are affecting it as well, but I had them put on not long after I first got the truck last year so I have no benchmark.

[Irish_Alley]

If you keep the speed below 60 you will see the mpgs go up one or two my 86 with a th350 and some other 350 would get 12-14 depended on how I drove it and where I got gas. If I got it from the cheapest place then it would be lower but if I spend more if would go up driving it the same way and all.