I have a bone stock 1996 civic ex. I bought the car as it's easy to work on and it's great mpg. Well, as we all know the ex has stupid short gears (imo). I average about 32-35mpg as of now.

I am wondering if I could switch it out with a different d-series transmission that would maybe be a little more efficient, and exactly which models I should look for. I cruise on the high way going 75mph at 3500-3900rpm (don't know exact.)

Any help would be appreciated.

 

The DX, A000 transmission would be perfect for you. Very long boring gears. Btw when you swap it out could I get the ex one?

 

You seem to be doing fine for a 96-00 Civic. You'd probably gain only 2-3 mpg from the swap.

If you really want a jump in mpg, buy an HX or VX.

 

^Backing "RonJ@HT" with respect to his response. Most people don't seem to realize that there is some thought from the factory relating engine speed to wheel speed. In short, they've geared each engine accordingly. With that said, realize that the engine is derived from a time when 55mph was the speed limit. Combine that with the threshold of wind resistance working against you and you might find more MPGs by slowing down a bit. Also, if you're serious about gaining MPGs you might consider installing a vacuum gauge.

Alternatively if you're super serious, get a complete HX swap or Civic HX/VX (as RonJ suggested).

 

I was surprised to see that my Si turns four grand at 70 mph when I got it a few weeks ago. I've read about swapping fifth out to bring down the rpms a bit, but I don't think I'm going to do that.

 

Why would you want your top-of-the-line (EX) grocery getter to become even more boring by switching to a longer gear ratio just to get a few more mpg's?

 

I wanted the ex model as it is fully loaded. Power windows, sunroof, cruise, a/c...the whole 9. Its not a race car nor do I need it to be one ( I have a k20a2/6 speed ep3 for that.)

If throwing a longer geared transmission in it won't net me much gain then so be it. But I wanted to toss the idea out there to see if it was possible.

 

The DX's highway MPG isn't too far off the EX's. The EX doesn't have stupid short gearing. The gearing also matches the engine.

 

ecomodders site ftw.

 

95 EJ1 D16zc sohc vtec coupled with an A000 DX Trans reporting in...above info is accurate, my mileage doesn't really differ too much from an ex trans if you drive conservatively..in fact, trying to push the longer gears from time to time can burn more fuel than with the EX trans.. 2-3mpg difference max here.

 

Wouldn't the biggest difference in gas mileage between the EX and other models (SI not included) be in the amount of time the Vtec is engaged, rather than transmission gearing?

 

When at cruising speeds you're never in vtec. Only when you get on it is when you start burning fuel.

 

The hx and ex trans are identical except for the final over drive gear

The most effecient gear box comes from the 92-95 civic cx/vx. The hx had lx/dx gear box, the main gain in the hx fuel mileage is the ability to drop into 3 valve operation and restrict fuel in lean burn in 5th gear at over 2600 rpms

For reference I get better mileage with my ex tranny just because I can enter lean burn at 52mph instead of just around 55mph on the hx gear box

It's been beaten to death on the ecomodder forum but there is no mileage gain from a lower overdrive gear to justify the work involved to swap it.

A y5 head swap with supporting ecu and 5 pin 02 harness would be more beneficial, but you would have to be pretty through in your Craigslist salvage yard scounging to find an hx