rear suspension & gasoline

I have a Astro van 1992 with the rear suspension springs made of carbon fiber. Can I install the same suspension springs to my second Astro van 1995 AWD. My Astro Van 1995 AWD use a lot of gasoline, more or less 25 liters for 100 km., what could be the problem? :wink: Thank you for your help.

i always say start with a good tuneup! check your air filter and gas filter, cap rotor, pcv etc etc after that see if your fuel economy is any better.