Does anyone know what could cause a 1990 crx hf to not be getting the mileage it should, I have to shift under 2k no revs at all and no quick takeoffs just to manage 40. I don't believe this should be needed, but correct me if I'm wrong. Thanks for any help.

Ps. The egr system needs to be changed, I don't know if this has any effect, this is just the only problem that it has at the moment

 

Just wondering when was the last time the car had a oil change and full tune up? thats usually the basic answer for gas mileage lost. it could be tires but i dont think i would do it drastically.

 

If the EGR is not working then you should have a check engine light. If that's the case, that is why your MPG is not as high as you expect it.

 

do you have the stock tire size? If not, your ODO is going to be off, and so are your mpg calculations.
Tire pressure?
I get 40 in my stock Si

 

Also have to take in to consideration the 10% Ethanol in gas these days. It will bump your MPG down. Try finding ethanol free gas station, and compere the MPG.

 

It's not just the EGR valve. The ethanol is destroying the parts slowly, yes. But a bigger problem is happening, I have another CRX HF and I have never reached the bottom of the gas tank. I've noticed that the pressure is not staying constant. I had a 1991 Honda CRX hf and it exceeded the projections by alot. 48 city and 56 highway. The best it ever got was 62mpg. three times but that was at 60 Ave speed. Now I have 1989 honda crx hf Ave 42 city and 50 highway. the issue is after refueling after 3 gallons used mpg was way higher than after using more than 7 gallons. I can't reach 8 1/2 gallons off one tank. after 7.5 gallons used car won't start easily