How to Increase Fuel Mileage on '88 Chevy P/U?

Try small things before moving to anything drastic. For example, check the gap on your spark plugs, check/ change your air filter, run synthetic oil, make sure you don't have any air leaks, and even try raising the tire pressures. These are all ways to increase your fuel economy easily and affordably. I've noticed an increase in fuel economy even by changing the weight of synthetic oil. I run 40 psi in my tires and that helps me pick up about an extra 10 - 14 miles per tank over running 30 lbs, plus I get much more even tire wear. The other thing that will drastically impact the fuel economy is driving technique. For example, if you pay attention much farther down the road and you see a light that might change soon - let off the gas and let the car start to coast, rather than accelerating until the light turns yellow, then accelerating more to catch the light before it turns. Same goes for when you see people slowing down far ahead of you, let off the gas instead of slamming on the brakes then having to accelerate to catch back up. It's little things like this that make the difference (for me at least) between 24 mpg and 28+ mpg. Also, as a side note, I drove cars fairly hard as a teen. It was fun at the time; I'm pretty sure things haven't changed much, in that regard, when referring to teen drivers today...

Since your truck is OBD1 the EFI is fairly primitive. It is very helpful to keep an eye on the ECM and sensors for issues that may be robbing your mileage. The most common issue is the truck not entering closed loop so the O2 sensor is not trimming your fuel input. There are no cost effective hand helds anymore. I recommend getting an ALDL cable, usb to GM OBD1. There are some on ebay for 60 and the software is free. Once you figure it out you can read codes, senor inputs, ECM parameters and outputs. Handy.

the guys are on the money I live in polk county fl and in the last year ive worked on 6 of this luckily I have a MATCO SCANNER for OBD1

If there is any obstruction to your air intake you cold remove it, or change it. I saw one of these trucks recently that had alot of money put into it. Fuel mileage increase was the desire, so we started looking. we found he had a door sticking shut in his air cleaner. after it warmed up. it was the spring type. The ductwork from the fresh air intake tube can sometimes have obstructions that are designed to affect flow or sounds. see if yours is clear. and open. To add to what crism said, the emissions people have a 32 point checklist that contains his comments and even more. you can see what they have in your area. I have also heard that shutting it off to avoid extended idle is a great help.