I have a 91 RS 305 with around 170,000 miles on it its developed a slight lifter knock when its cold it idles constant but a little rough. On my last tank of gas for some reason I got around 96 miles! Now if I do the math on that with around 15 gallons of usable fuel that’s less than 7 mpg! This is outrageous I didn’t drive it into the ground just lightly around town. I usually get around 200+ miles to a tank. I am going to change the o2 censor tomorrow but it was new just a couple months or so ago. I could really use some advice here I am just a poor college student and I cant afford this 7mpg stuff!

 

Do a good tune up.

02 sensor
Cap/rotor
plugs/wires

Those 5 things will go a LONG way in making a good running motor.

are you sure you have lifter knock??? and not a bearing, or exaust leak? What kind of oil are you running, and how long has it been since the last oil change?

 

I change it at least every 3000 miles and I usualy mix it up between some synthetic and normal 5w-40 but the know has been around for 20,000 miles or so. But I never really investigated what is was I just assumed it was a lifter.

 

Check for leaks in the lines....