2001 civic ex 5 speed mpg issues

[bmk6795]

Alright guys i have a 2001 civic ex coupe and cant figure out why im getting 27 mpg. Gonna list everything that has been done to the car so you guys know what im working with. D17A2 engine, rebuilt head, every seal in the head is new, head has been shaved, new rear main seal, new head gasket, new alt, new water pump/timing belt, new belts all around, tranny over hauled (every bearing in tranny is new), new excedy clutch kit, 10lb flywheel, aem cold air intake, sittin on 17" rims with new tires, 0 gauge big 3 done in engine bay, single 12" sub (sub and box weigh about 60lbs together), 2 amps pulling about 1000 watts, new ngk iridium plugs, fresh oil change, and new filter on the air intake. Thats about it. All of these parts have about 4-5k miles on them. Before rebuilding everything i took a beach trip and got about 41 mpg (all highway). Didnt really check much other than that trip. Now im getting about 27 mpg weekly. I drove the car like a saint this past week shifting at 3k for 1st and 2nd and at 2.5k for third and fourth, didnt down gear at all, didnt rev ever and got the same exact gas mileage as i did when i beat on it every once in a while during the week. Any ideas why this motor, made for fuel efficiency, is getting such low gas mileage?

 

[sr6000]

I get 29 or 30 in town and road trips 40-41

 

[bmk6795]

I get 29 or 30 in town and road trips 40-41

Welll about 75% of my driving during the week is highway, which is what makes me wonder why its so low, however, it really seems to get about the same gas mileage whether im on the interstate or driving around town. Oh a detail i forgot, when im driving on the interstate at 75 mph im sitting at 3.5k rpms, is this right? In my girlfriends 93 civic and my old 87 accord, i never went about 3k rpms on the highway unless i was doing over 80.

 

[Osiris19]

Keep it under 3k I guess?

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[young_]

You would be surprised the effect aftermarket rims can have on gas mileage. 17's are particularly large for a civic. Not sure about your year model but my 1996 comes stock with 14" wheels.

Other than that and the sound system, idk. I don't think the sound system is the culprit though.

Also you mentioned plugs and an air filter. How about your distributor cap and rotor button? Fuel filter? Etc. I would try a complete tune up and report back.


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[sr6000]

The EX model has sportier gearing than the other models ie. higher revs on the freeway, but faster acceleration. You don,t have cap and rotor, this is a coil on plug engine. Try cruising about 70.

 

[Avant Uprising]

seafoam the engine run additives every couple thousand miles. yes a stereo system will affect cause it pulls from the alternator and it has to feed the amp before it can give juice to all the other electronics properly. ex model has shorter gears. switch to a thinner full synthetic oil that will increase mpg.

 

[Pineapples]

That's the mpg I got since day 1 I bought the car brand new. Normally around 28 mpg, sometimes 26. There was a time that it hits 30 but it's rare. The only times I got over 30 is when I was on the freeway for a long time. Even switched to synthetic, even tried 0w20, and bunch of different type of additives. Nothing helped. Although, 0w20 did do a better job in the winter. Car only has 54k miles. In reality, I shouldn't have to add any additives. It is what it is.

 

[milagro33]

I get 30 city on my 96 EX 5 speed but its a D16y7 swap with a vtec head. I got horrible highway mileage though. Just put a new set of tires all the way around and it improved my highway mileage a bit.