How-To: Better MPG

[HeX]

For those of you looking to maximize your fuel efficiency, heres a useful list to review. I was able to comprise this list thanks to various input from forum members in another thread topic I started while addressing my relative poor mileage on my manual '97 Civic HX. These tips are relatively universal, so it should help out virtually any vehicle. This is in no specific order.

1. Driving Habits - controlled passive driving within the engines optimal performance
2. Local weather factors - extreme heat inducted into the engine will reduce efficiency just as frigid weather forces the engine to work harder to warm up.
2a. Lets not forget heavier usage of A/C in warm climates or turning on the car in order to pre-heat during frigid periods.
3. Wheel Weight - consider your wheel material & diameter
4. Tire Pressure & Quality - crappy tires dont help
5. Cabin weight (more weight = more gas consumption)
6. Air Filter - replace/clean regularly and/or upgrade
7. Fuel Filter - should be changed every year or 2
8. Proper Oil & Filter - not just proper viscosity, but quality oil may help at least clean up old gunk inside
9. "Check Engine" Codes - most engine codes indicate a dysfunction that impedes optimal functionality and thus fuel efficiency
10. Spark Plugs & Wires - check the plug gap
11. Distributor Cap & Rotor - change every 60k miles or so
12. Clean out EGR Chamber; Clean or Change EGR Valve - code P0401
13. O2, IACV, PCV or TPS Sensors - some Bad sensors should throw a code, but not all
14. Suspension/ Alignment Issues - some worn parts can impede your ability to move with ease
15. Check/ Adjust Engine Timing - if spark and fuel delivery arent in sync then fuel is wasted.
16. Reset ECU - not recommended unless necessary; ECU may take several days/weeks to recalibrate while driving.
17. Clean/Unclogged Fuel system & Injectors
18. Replace Thermostat every 80k miles - If a malfunctioning Thermostat is stuck in open loop, it'll reduce fuel efficiency. (OEM preferred)
19. Valve Adjustment - Improperly adjusted valves will affect mileage when the valves dont open or close precisely. Noticeable ticking may be sign of "Valve Lash".

Feel free to suggest anything else to add to the list.

 

[Trekk]

Look ahead while driving, to many people drive up to a red light at full speed then hit the brakes. It's better to see the light a head of time, and slow your speed in an attempt to not get to the light before it changes back green.

Also Hot air intakes can help a little.

 

[HeX]

Look ahead while driving, to many people drive up to a red light at full speed then hit the brakes. It's better to see the light a head of time, and slow your speed in an attempt to not get to the light before it changes back green.

Now youre just nitpicking. That kind of driving is done by poor drivers.

Also Hot air intakes can help a little.

That is the 1st time Ive ever heard someone say hot air is beneficial for air induction. Hot air doesnt help at all.

 

[Trekk]

Now youre just nitpicking. That kind of driving is done by poor drivers..

No by keeping a mass moving, you need less engine load to get it moving which can save you a ton in MPG.

That is the 1st time Ive ever heard someone say hot air is beneficial for air induction. Hot air doesnt help at all.

So that must mean it is wrong because now you are the expert?

Let me guess a bigger exhaust diameter helps also?

 

[mikekh10a]

So exactly what psi for the tires will actually make a difference in MPG?

 

[2slo4u]

Every tire is different and will have its own psi rating. Just a thought. The new Prius with its 17 inch rims get the same amount of mpg as the ones with 15 inch rims.

 

[EJackBauer8]

Look ahead while driving, to many people drive up to a red light at full speed then hit the brakes. It's better to see the light a head of time, and slow your speed in an attempt to not get to the light before it changes back green.

Also Hot air intakes can help a little.

This is true I've been doing this for the past 3 weeks and shifting at around 2.5-3k. Also cruising around 50mph in 5th gear or just cruising in a higher gear is better for gas.

Sent from my Galaxy S-Triple

 

[HeX]

No by keeping a mass moving, you need less engine load to get it moving which can save you a ton in MPG.

Fully agreed. i just wanted to keep this list more on point of the less obvious tactics.

So that must mean it is wrong because now you are the expert?
Let me guess a bigger exhaust diameter helps also?

Slow down the attitude, buddy. All I said is that Ive never heard any proven research from an expert that heat helps air induction in any way, so its not easy to believe. So if you have some facts or educated opinions on this, please do share.

This is true I've been doing this for the past 3 weeks and shifting at around 2.5-3k. Also cruising around 50mph in 5th gear or just cruising in a higher gear is better for gas.

I edited my comment next to "Driving Habits" since the suggestion of driving under 2k below 60mph is more for the HX models. You gotta drive within the optimal parameters of the given car, which of course varies.

 

[HeX]

Ive recently done some extensive research on the "Hot Air Intake" method, reviewing various comments and results from various forums. The fuel efficiency increase yielded is about 1-3MPG at best and only under very specific temperature conditions; not being too hot, or cold, or humid. Without optimal conditions, you will lose MPG. Simply put, its just not worth the time or effort for an already efficient vehicle.

 

[HeX]

I recently had OsideTiger.com service some used 16Y5 injectors. After installing them 5 days ago, I'm quite satisfied so far. Not only do they look like new, but I can clearly feel a smoother flow through the engine resulting is easier acceleration and quicker starts.

This is how I received them; polished with new filters, tips, o-rings & the old parts in a bag along with flow test results before & after the servicing.

Im also currently experimenting with a fuel system cleaning process to hopefully cleanse any possible deposits in the fuel lines from the tank. I will post my fuel efficiency results, if any, after a few weeks.

 

[HeX]

Overdue Update!

I recently had OsideTiger.com service some used 16Y5 injectors. After installing them 5 days ago, I'm quite satisfied so far. Not only do they look like new, but I can clearly feel a smoother flow through the engine resulting is easier acceleration and quicker starts.

10 months later and I have no complaints. All is working very well.

Im also currently experimenting with a fuel system cleaning process to hopefully cleanse any possible deposits in the fuel lines from the tank. I will post my fuel efficiency results, if any, after a few weeks.

I experimented with adding a small amount of Techron fuel system cleaner into each cylinder combustion chamber by removing the injectors & injecting the additive in with a small plastic syringe. My theory is that having a momentary larger combustion will blast out some heavier deposits that a standard fuel additive cleaning may not break up. It did seem to provide a more free-flowing response feel although a significant feel should likely not be something easily or heavily observable.

FYI, I have also been performing occasional fuel system cleanings using double the recommended amount of Techron additive at just half a tankful refill. My reasoning is that when a professional shop performs a fuel system cleaning they use a brief run of a few ounces of pure fuel system cleaner at the injectors, bypassing the gas tank & fuel lines. This may allow for gas tank & fuel line deposits to later make their way into the previously cleaned injectors.

Thus, I theorize that a similar home method consisting of a 20-gallon Techron treatment (20 ounces) added to roughly 4-5 gallons is concentrated enough to better clean out deposits from the gas tank and fuel lines all the way through the entire fuel system. Being added to just 4-5 gallons is low enough to heavily clean out the entire system without providing prolonged exposure to such strong cleaning solvents that could potentially damage components. I've performed this on a few other cars as well and the improvement was observable within the first refill.

Ive been doing this on my Civic roughly every 3000 miles for almost the last year with no issues. My Civic runs exceptionally smooth while having 160,000+ miles and starts up incredibly quick. I chose to do this for roughly a year since I dont believe this engine ever had a fuel system cleaning in the past. After a year of this process, I intend to spread it out to perhaps twice a year or every 6000 miles. I believe doing this should keep my fuel system very clean from here on out. I also intend on cleaning out the EGR chamber every other year or so while replacing the fuel filter yearly.

Any comments are welcomed as always.

 

[RonJ]

2. Local weather factors (heat = less MPG)

Feel free to suggest anything else to add to the list.

First off, I love this thread. I think good gas mileage is not emphasized nearly enough in the Civic community. So, kudos to you OP.

Point #2, though, I somewhat disagree with. Cold weather lengthens the time for the engine to warm up, thus prolonging time in open loop, thereby reducing gas mileage. The main factor in reducing gas mileage in hot weather is the increased usage of A/C, which makes the engine work harder.

Your readers should also know that an engine that runs cold due to a stuck open thermostat will reduce gas mileage because the engine stays in open loop (preprogrammed rich mode). The take home message is replace your thermostat at least every 80K miles and use an OEM thermostat.

An exhaust leak near the primary O2 sensor will similarly reduce gas mileage due the false "running lean" signal to the ECU. So readers, please maintain your exhaust gaskets, and also checked for cracks in the exhaust manifold.

Finally, FIX ALL CEL CODES. In general, ANY CEL code will reduce gas mileage.

Thanks Hex.

 

[HeX]

First off, I love this thread. I think good gas mileage is not emphasized nearly enough in the Civic community. So, kudos to you OP.

Point #2, though, I somewhat disagree with. Cold weather lengthens the time for the engine to warm up, thus prolonging time in open loop, thereby reducing gas mileage. The main factor in reducing gas mileage in hot weather is the increased usage of A/C, which makes the engine work harder.

Your readers should also know that an engine that runs cold due to a stuck open thermostat will reduce gas mileage because the engine stays in open loop (preprogrammed rich mode). The take home message is replace your thermostat at least every 80K miles and use an OEM thermostat.

An exhaust leak near the primary O2 sensor will similarly reduce gas mileage due the false "running lean" signal to the ECU. So readers, please maintain your exhaust gaskets, and also checked for cracks in the exhaust manifold.

Finally, FIX ALL CEL CODES. In general, ANY CEL code will reduce gas mileage.

Thanks Hex.

Thanks for the support, RonJ. Its a bit surprising that many seem to have forgotten or at least partially neglect that these cars were designed to be reliably efficient cars above all else.

I'm glad you brought up the weather conditions comment. I will admit that I lived in tropical conditions when I originally posted and now I live in frigid winter weather. Thus, I've learned more so I have appended that comment. The best summation may be that extreme heat inducted into the engine will reduce efficiency just as frigid weather will cause the engine to work harder to run at an optimal temperature. Cool weather is optimal. I also added your thermostat comment as #18.

Thanks for the contribution.

 

[HeX]

I added #19; Valve Adjustment.

I came to learn that an engine ticking sound I experienced is an issue called Valve Lash; when intake and/or exhaust valves have loosened over time causing moving parts to tick occasionally against one another. When these valves dont open or close precisely, the cylinder ports will open slightly late or early and negatively affect combustion, thus fuel efficiency.

Performing a valve job is surprisingly simple so long as you take your time adjusting each valve correctly. Unfortunately, I havent come across any general guidelines on when to perform this maintenance, which leads me to believe it should be done only when you observe the sound or are losing fuel efficiency and are unsure of the culprit. As always, please feel free to share your knowledge and suggestions.

 

[gbaby2089]

OP, what kind of mileage do you get?

 

[HeX]

OP, what kind of mileage do you get?

When I originally purchased my HX I was getting about 28mpg. Ive done quite a few changes and maintenance and now average about 33mpg prior to the valve adjustment. I will also be going back to HX rims soon but I will be recording my mileage difference prior to installing the HX rims.

 

[gbaby2089]

When I originally purchased my HX I was getting about 28mpg. Ive done quite a few changes and maintenance and now average about 33mpg prior to the valve adjustment. I will also be going back to HX rims soon but I will be recording my mileage difference prior to installing the HX rims.

Do you do a lot of city driving?

 

[HeX]

Do you do a lot of city driving?

I do. Primarily all city driving. I believe the valve lash I had and the bigger SI rims have been culprits to my current MPG average. I will confirm that soon enough. Do keep in mind that all the tips I've provided are universal tips used by many car owners who get improved gas mileage, so I am not the sole example of these tips. I also like to drive a little spirited here and there but nothing excessive. I am fully aware that I own an HXand not a sports car, unlike many other Civic owners out there.

 

[gbaby2089]

I do. Primarily all city driving. I believe the valve lash I had and the bigger SI rims have been culprits to my current MPG average. I will confirm that soon enough. Do keep in mind that all the tips I've provided are universal tips used by many car owners who get improved gas mileage, so I am not the sole example of these tips. I also like to drive a little spirited here and there but nothing excessive. I am fully aware that I own an HXand not a sports car, unlike many other Civic owners out there.

Oh, I've used many of this tips in the past, that's why I averaged 33 mpg out of a dying DC4 and 38 from my Fit, 33 just a bit low if there was substantial highway driving. Now it all makes sense

 

[HeX]

MPG Update

I just filled up a full tank for the first time since adjusting the valves and I calculated 36.3 MPG (299.75 miles / 8.25 gallons) on usual mixed city & highway driving. Thats a rough increase of 3MPG. I'll continue to report my averages after a few fill-ups.