[Average Joe]

[QUOTE=Lancialonnie;8796188]This is a frustrating topic for me! I had read the many posts from people getting 15-17 mpg and that was the range I wanted to be in so I could daily drive my 72 fleetside longbed.
I bought a new Blueprint Engines 383, 430 h.p. and had an early 700r4 non-electronic lock-up rebuilt and upgraded. I have 18's and haven't verified but it should be the original 3.07 gearing. Got everything installed with FITech supplying the fuel and started putting on some miles.

First oil change was at just over 600 miles and I've been logging every tank. Mostly around town with some country driving at 60-65 and I was getting just over 7 mpg! Very disappointing to say the least on mileage but wow is it fun to drive! Smooth, great acceleration, sounds great, no issues with performance.

I purchased a complete MSD ignition system (distro, 6AL, coil) and had an X pipe installed and starting using Drive instead of OD in town. Now I am just over 9 mpg and I did a couple freeway trips at just over 12 mpg. I don't know of anything else to do to get the mileage up.

You are on the right track. Keep tinkering and logging every fill up. The people that are getting 14 plus mpg hwy have put a lot of effort into achieving that number or are using creative math.

Your 383 is pretty wild in terms of gas mileage being the optimum goal. Typically better mpg is achieved with milder cam timing. IE less duration and lift. Compression is efficiency but staying out of detonation with a smaller cam and higher CR’s is much more challenging. In other words, it’s tough to have your cake and eat it too.