any d series engine with vtec-e like (d15z1, d15z3, d16w5/7, d16y5)? should be best for economy, bear in mind that this is vtec-e and not vtec, on the contrary if you want both economy and power, go for the 3 stage vtec engines likes d15b (3 stage), d15 z7/z8 (3 stage). you are likely to only find the Japanese DxxZ(no) engines in the local market, and these engines need a lot of hunting after , the d17 series is a little uncommon but the d17a5 in it also has vtec-e