Need help to improve MPG
 

I'm looking for some better input than I'm finding on google on how I can improve my gas mileage. Im driving an all stock 99 Ex d16y8 manual with 144k. I have done the following:

New timing belt, water pump, thermostat
Complete Distributer (OEM)
Spark plugs (NGK copper)
Plug wires (Duralast)
Fuel filter (Az Filters)
Clean throttle body
Oil and filter change (5w 30 w/ Honda filter)
Air filter (OEM)

My next steps are to clean the VTEC Solenoid and possibly seafoam if all else fails. I'm still only getting approximately 26-28 mpg right now, 30 mpg if I'm extremely light on the throttle. And no CEL or MR. Also want to note that when i accelerate my fuel gauge will drop a quarter tank and slowly rise once I'm at a steady speed.:thud:

Re: Need help to improve MPG
 

Sounds about right. Start hypermiling.

I would seafoam it. the whole gas guage thing may be the rear suspension has some slop and the weight transfer from accelerating causes the gas to move to the rear of the tank so the guage will read low then when u reach speed it will equal out as the weight becomes properly distributed


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Re: Need help to improve MPG
 

Shift earlier, coast more in gear with clutch in foot off the brake, don't accelerate as fast, drive below 70 on the freeway if you aren't afraid of getting run off the road, try driving in just socks, etc.

Re: Need help to improve MPG
 

Why drive in just socks? lol

Re: Need help to improve MPG
 

better feel for throttle

Re: Need help to improve MPG
 

strip your car....weight reduction y0 ! im liking the driving in socks idea it's a good start +1

Re: Need help to improve MPG
 

Check tire pressures as well. I have a 1997 EX/ D16Y8 and it routinely gets 30-31mpg mixed driving. A lighter weight, smaller sized tire/wheel could also help (if you have aftermarket stuff or whatever).

Re: Need help to improve MPG
 

Check with a scan tool if you have a lazy 02 sensor, if you do replace it with a new one that will help your mpg.

My 92 eg gets 29 city. It's a five speed D16Z6 after experimenting with my driving i get better gas mileage shifting at or around 4-5 rpms. Reason for that (only one i can think of) is because I'm keeping the rpms closer to the power band making it do the engine doesn't have to work as hard to move the car.

When i was shifting at 2500-3000 i was getting 26 around town.


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Re: Need help to improve MPG
 

Haha if you really want those MPG's don't use your ac xD That should really help.

Re: Need help to improve MPG
 

Get a cx vx trans pump up tire pressure to 40ish get a scan gauge.

Re: Need help to improve MPG
 

First off I want to say thank you for all of your input it has been extremely helpful and second this forum is a far better than clubcivic. I posted this same thing on there and the only input I got was that I had to be calculating my mpg wrong.

Also to add: yesterday I cleaned my IACV Andy VTEC solenoid. Which has definitely made a big difference in how the car accelerates and idles. The screen in my IAC was extremely clogged with build up.

Now to answer your questions. This is what I am getting for highway driving. I make a 115 mile drive almost every week which is why this is such a major concern for me.

Re: Need help to improve MPG
 

The socks thing is actually a good idea, I've tried it before and personally for me I have a better feel for the throttle in my shoes.

I will definitely up my tire pressure for my next trip. I believe my tires (185/65/14) are at 36psi right now.

I very rarely use ac (I live in Seattle)

I usually shift around 3k in the city. And on the highway I will shift around 4 or 5. Which really shouldn't make much of a difference since I only do that getting on. And the freeway I'm on the speed limit is 70 so I cruise around 73-75 at 3200 rpm

Re: Need help to improve MPG
 

Seattle is pretty hilly. Revving for torque to climb those hills is killing your mileage.

Re: Need help to improve MPG
 

I don't live in downtown Seattle. I live in the burbs. Not many hills. And the drive I make is to eastern Washington.

Re: Need help to improve MPG
 

oxygen sensors will prob give you the best bump in mpg at that milage. also look into purchasing tires that are designed for better mpg. if thats not in the budget you can always bump your tire pressure by a few psi. hope that helps

Re: Need help to improve MPG
 

Have you done any maintenance to your PCV system? Could be losing a few mpg's there.

Re: Need help to improve MPG
 

I'm learning a bit too, what does cleaning the VTEC solenoid help with? I understand the IACV deals with your idle and what not.

I'm not saying exactly that this needs to be replaced since you have no CELs, but when was the last time your Catalytic Converter was replaced? That along with the o2 sensors matters a quite a bit for MPG.

Re: Need help to improve MPG
 

Check tire pressures religiously and reduce/remove all excess weight. You could try reduce frictional resistance somewhat by flushing the transmission and replacing it with AmsOil or equivalent. Apart from that, you've done pretty much everything I would suggest

Re: Need help to improve MPG
 

Readjust timing to spec under hood also. It might be off a bit causing incomplete combustion.

Re: Need help to improve MPG
 

The best thing to modify is the part that sits between the driver's seat and steering wheel. =)

My 378,000 mile D16Z6 Civic consistently gets at least 33mpg combined or 35-42mpg on the freeway.

Drive smoothly and anticipate upcoming road conditions and have good situational awareness. You ever see those dumbasses that drive up to the bumper of the slower car ahead, then brake, then finally switch lanes? Make sure you always have somewhere to go on either side of your car and preemptively change lanes to keep a steady pace.

Aircraft pilots learn about energy management. The same principles apply to driving a racecar or a car on the street.

Re: Need help to improve MPG
 

If your not concerned with speed swap out that Si transmission and put on the DX or CX transmission.

Re: Need help to improve MPG
 

You have to use the pinky toe to save gas.

Re: Need help to improve MPG
 

Running tires at 40psi would be my suggestion.
My 99 Civic Lx AT gets 33-35mpg on the freeway, my wife drives 800 miles a week in this car, so MPG is always on my mind.

Do you fill up at the same gas station every time with the same grade? Or are you switching brands and grades?