This is quit frustrating. Last tank I barely got 230 for a tank of gas on my 96 DX coupe and I can't figure out why. I've even been driving it nice and slow too, rarely even reving past 4500 rpm. I've been getting between 230-260 per tank lately. I've replaced very recently, spark plug wires, spark plugs, fuel filter, distributer cap and rotor, and I had my cracked exhaust manifold replaced by honda for free. I still get bad gas mileage. I have 83,000 miles. Is there anything else i'm forgetting to replace or fix here as far as tune up stuff goes or as far as general routine maintenance? The only thing that I can think of that would be affecting my gas mileage would be my tires, which are 205/50 15's. But still, when I got the car, driving it on 175/70 13's, I could get 350 to a tank, I don't think tires would affect gas mileage that much.

 

The only thing that I could think of are your tires' psi correct? That, and if your 15's are heavier than your 13's, but like you said, it shouldn't affect it that much...

 

whats a good psi to keep 205/50 15's at? They are kumho ecsta supra 712's.

 

I was told that you should keep the same PSI as what the car manufacturer recommends. But I always questioned that when it came to "plus-sized" wheels and tires. To play it safe, I use what the tire says (the recommended psi should be stamped somewhere on the tire).

 

also, you're coming up on that 90k service time. not sure if that would change anything though. i barely get 230 to the tank (ex sedan). i wish i would have ever gotten 350 to a tank.

 

what needs to be done at a 90k ? Replace timing belt and water pump, maybe adjust the valves? So far my list of stuff to replace for 90k are both my axels, oil pan gasket, valve cover gasket and lower engine mount, timing belt and water pump

 

dude, check your air filter...it might just need to be replaced...either get cheapo replacement, K&N, or even a shortram intake.

I have 98 EX Coupe...I have 205/45R16's, and I get 350 per tank and when I fill I only put in little over 10 gallons, and the tank holds 11...


but yeah I was experiencing crappy gas mileage, and I looked at my air filter and it was crapped up, so I put on my intake and I gained 60 miles per tank...I was getting 290 before...

 

What mods do you have done to the car, such as intake and exhaust? those will affect your milage.

Also the tires will affect your milage. more tire to spin = more work for the engine to do = less efficiency. also, when you change your rim and tire size, unless overall it is EXACTLY the same overall height as stock, your odometer is going to rack up miles slower. had a car once that we went from a 70 series to a 75 series tire on and the speedo was off by 5mph, showed we were going 5mph slower than we actually were. our fuel milage numbers were always off after that too.

One more thing, when you go to a wider tire, you are going to lose milage. More contact area with the road means there's more tire to move, therefore more work the engie has to do. All of those things could be having an effect on your milage.

If you've changed any part of your exhaust, you are also going to notice a change in fuel milage. your engine is dependant on the backpressure of the stock system to run correctly. If you have a higher flow system on your car but still dumping the same amount of fuel in as your system was seeing with the stock exhaust, most of your fuel is actually flowing right out the exhaust valve when they are overlapping the intake valves during their duration of lift because there isn't enough backpressure to hold the fresh fuel/air flow in. That would also create a lean condition in your engine which will eventually cause damage.

Hope this helps.

 

STOCK96civicDX;

can you explain more about the lean condition and what kind of damage it would cause, like what are the symptoms and how they can be fixed?

 

Actually if you want better mpg increase the tire pressure over stock by 2-3psi. Yes ride might be a little stiffer, but it's well worth it in my honest opinion.

Also you didn't mention did it get hot these past few weeks?

Did you gap the spark plugs right? Stick some fuel injector cleaner in every 5000 miles? Have you switched to synthetic oil?