i have a 94 civic dx 2-door with sohc 1.5 and 5-speed the only option is a/c, no power steering, windows, nothin. it has 270,000 miles and still gets 37-38 miles per gallon, but i was wondering if there were any relatively cheap mods to help boost the mpg. i live in virginia and the gas is now $4.15 for high test and steadily rising. the car runs great and has always had high test put in it, unfortunatly i can no longer run synthetic oil, as its lettin too much oil in the cylinders and will foul the plugs within 2 thousand miles. regular conventional oil has seemed to solve that problem. im up for all options, as performance is of no concern, the car wont get out of its own way anyway so im focused on mpg. any help would GREATLY be appreciated.

 

you've been running HIGH OCTANE? WHY????

Synthetic oil hasn't been fouling your spark plugs man....running high octane has!

your owners manual says to use 87 octane. Absolutely no reason for you to be using 91 or 93. None.

You'll get better mileage just by going to 87 octane!

Keep using synthetic oil, too.

 

Yup, you've been burning $$$ like crazy . Just use regular and it should stay the same. That kind of milage is great, just leave as is.

 

yeah bro definitely wastin ur cash on the higher octane fuel, definitely definitely definitely dont need to be doing that... until ur built and boosted with a good tune, u can use 87 all day all night and be fine... if ur in search of better MPG look for someone with a VX hatch that did a swap and has their VX motor lying around still, give'm like 2 bills for it and ur golden.. otherwise just stay up to date on ur filters/fluids and thats bout the best u can do...

 

i always used the good stuff just for the cleanliness, i like clear fuel rather than yellow stuff. and as soon as i switched oils, the plug problem stopped, its been 9000 miles on conventional, and it still runs good. i guess now would be a good time to switch fuels, ill probably just change the filter a little more often, im 27 years old and have never touched an 87 octane pump, even my 77 f-150 gets 89, and thats just an old farm truck, but i do love it to death, im definetly happy with my current mpg in the honda, but i just feel like it could do better and id love to see it do so, ive almost considered puttin some under car shields on it just to help the air flow better. i work at a mazda/chrysler/jeep dealership so weve got those sittin around

 

im not exactly a honda enthusiast, ive despised them for years, but the gas is forcin some of us to change our minds. but what exactly is the difference in the cx vx and i think ive seen an hx also, are they just differences in the camshaft, valves, and head/intake ports?

 

There are a few important factors that I would consider in my quest for higher mpg efficiency.
First off, your driving techniques make a huge impact on the how much fuel you use. With the mpg that you stated, it sounds like you are doing pretty well there already. Do a google search for 'hypermiler techniques' or check out some websites like gassavers.org. The best thing about driving technique is it can increase your fuel efficiency no matter what car you are driving.
Next, is this car an automatic or manual transmission? Depending on if you do alot of highway driving, and your driving style, you might consider swapping to a five speed. Also, hypermiler techniques are usually easier with a manual transmission.
Then I would consider aero mods to reduce drag such as the under-car panel that you mentioned. This would help out with your higher-speed and highway cruising efficiency.
If you are going to go through any of this trouble I would take a look at the most simple things first. If you are burning oil then you are not making as much power, so you will probably be using more gas to move the car along. Get this fixed.
If you can run a lower viscosity oil that might make a slight difference in engine efficiency and performance.
Basic maintenance is important so make sure your fuel and ignition system are in good working order.
If you have any spare weight that you can strip from the car, do it. (do you really use that back seat?)
Then as these other guys have already said, there is no reason at all to be running more than 87 octane fuel in this car.

Hope that helps.

 

One more thing I forgot to mention.. Thin, low drag tires, filled with nitrogen, on lightweight wheels will help with unsprung weight and give you a very slight advantage.

 

[QUOTE=Artifactr]One more thing I forgot to mention.. Thin, low drag tires, filled with nitrogen, on lightweight wheels will help with unsprung weight and give you a very slight advantage. [/QUOTE

the guy at goodyear that installed my last set of tires put in that nitrogren **** without tellin me, an i have to admit the handling was severely worse than just using air... felt like my tires were made of concrete, i deflated'm and refilled with air and noticed a huge difference... i know they say that nitrogen is better for'm an gives longer tread life and whatnot, but i can attest that in my case nitrogen performed far worse than regular air... but all ur other info was very helpful...

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 83rs &raquo;</TD></TR><TR><TD CLASS="quote">i have a 94 civic dx 2-door with sohc 1.5 and 5-speed the only option is a/c, no power steering, windows, nothin. it has 270,000 miles and still gets 37-38 miles per gallon, but i was wondering if there were any relatively cheap mods to help boost the mpg. i live in virginia and the gas is now $4.15 for high test and steadily rising. the car runs great and has always had high test put in it, unfortunatly i can no longer run synthetic oil, as its lettin too much oil in the cylinders and will foul the plugs within 2 thousand miles. regular conventional oil has seemed to solve that problem. im up for all options, as performance is of no concern, the car wont get out of its own way anyway so im focused on mpg. any help would GREATLY be appreciated.</TD></TR></TABLE>

1. use 87 octane, PERIOD

2. accelerate a little lighter from stoplights

3. strip car of interior

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 1CaMw0nDeR &raquo;</TD></TR><TR><TD CLASS="quote">[QUOTE=Artifactr]One more thing I forgot to mention.. Thin, low drag tires, filled with nitrogen, on lightweight wheels will help with unsprung weight and give you a very slight advantage. [/QUOTE

the guy at goodyear that installed my last set of tires put in that nitrogren **** without tellin me, an i have to admit the handling was severely worse than just using air... felt like my tires were made of concrete, i deflated'm and refilled with air and noticed a huge difference... i know they say that nitrogen is better for'm an gives longer tread life and whatnot, but i can attest that in my case nitrogen performed far worse than regular air... but all ur other info was very helpful... </TD></TR></TABLE>

That is by far the dumbest thing i have ever heard. If your tires were like concrete it wasn't because there was nitrogen in there...It was because there was TOO MUCH nitrogen in there.

The point of nitrogen is that the molecules are larger and don't leak through the rubber as easily and they expand and contract far less then straight air. This keeps tire pressures where they belong to help tire life and gas mileage.

 

Ok quick q out of all this. I drive a 97 civic ex(d16Y8) on 89 octane. Is this a bad idea or bad for mpg? I mean I have always put 89 on all my cars. I put 89 on my other civic w/JDM D15B Vtec.engine is that bad for that engine too? Will lowering the octane make my car run better or give better mpg?

 

The simple answer is no. Lowering the octane of the fuel will not help your mpg, but it might make your wallet a little happier.
The fuel octane should be dependent on things like compression ratio, and ambient air temperature and density, so colder air and higher altitudes like if you live in Denver may constitute a change in fuel octane.
More importantly accelerate slower, stay out of vtec, use a lower highway cruising speed, and make your car lighter and more aerodynamic. These are the things that will help efficiency.

 

http://www.gassavers.org/index.php

Great reference for mpg crazy enthusiasts. They've got some good DIY mods and tricks on there to help increase gas mileage. Should help you as well.

 

ho bag is absolutely right, we have nitrogen at our shop, and it only has better qualities than air, as in it stays in longer and doesnt expand therfore raising pressure as your tires heat up, the car is a 5-speed and when i first got it i could only get about 32 mpg, so my driving technique has improved, i do mostly city driving, and i have 14" pep boys wheels and 195-60-14s on it, thanx for the links, i'll give them a try

 

i dont really want to strip the interior, as its all still there and in excellent shape. i have lowered my highway cruising speed to 65 and that has the engine doing around 2700 rpm. its not a vtec. and it only burns about a quart per 2500 mile oil change. if i floor it and run it thru the gears, it will blow smoke out the pipe, but thats the only time you will see it smoking

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Artifactr &raquo;</TD></TR><TR><TD CLASS="quote">The simple answer is no. Lowering the octane of the fuel will not help your mpg, but it might make your wallet a little happier.
The fuel octane should be dependent on things like compression ratio, and ambient air temperature and density, so colder air and higher altitudes like if you live in Denver may constitute a change in fuel octane.
More importantly accelerate slower, stay out of vtec, use a lower highway cruising speed, and make your car lighter and more aerodynamic. These are the things that will help efficiency. </TD></TR></TABLE>

actually, that's not entirely true. Higher octane gas doesn't have the potential energy of lower octane, i.e. it burns slower. 93 octane won't get a complete burn on a bone stock d15, therefore he's going to have unburned fuel going thru his exhaust system and catalyst, his o2 sensors will be fouled quicker thereby making his ECU get poor readings.

He'll get more realized energy by using 87 octane, thereby making more efficient use of the power available in the fuel, still getting good mileage (if not better since it won't need as much fuel to combust) and lighter wallet due to using 87.

 

Run 87 you will get better MPG as already said. unless your vehicle has a compression ratio of 10.5/1 you do not need and it is actually harmful to run the high octane. You arent fully burning your gas and its not good for the engine and thats whats fouling your plugs. Switch to 87 and synthetic oil...

 

Those are good numbers, but you can definitely do better. Pump your tires up to their max sidewall psi, stop putting premium fuel in (you don't need it), make sure your fuel and air filters are clean, brand new plugs and wires, cap and rotor, etc. After that, the easiest and cheapest way to better mileage is driving technique. I used to get the same numbers as you, before I started learning about hypermiling. Now I am getting 50+ mpg regularly, using some fairly simple techniques. You can learn all about them at gassavers.org or cleanmpg.com.

 

Lol... Nitrogen does make your tires concrete. You do know what most of our atmospheric air is made of right?

If you have a very high milleage mtor that is having oil issues you might think about trying out AutoRX, good stuff for cleaning gunk out of your motor.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by chimmike &raquo;</TD></TR><TR><TD CLASS="quote">

actually, that's not entirely true. Higher octane gas doesn't have the potential energy of lower octane, i.e. it burns slower. 93 octane won't get a complete burn on a bone stock d15, therefore he's going to have unburned fuel going thru his exhaust system and catalyst, his o2 sensors will be fouled quicker thereby making his ECU get poor readings.

He'll get more realized energy by using 87 octane, thereby making more efficient use of the power available in the fuel, still getting good mileage (if not better since it won't need as much fuel to combust) and lighter wallet due to using 87.</TD></TR></TABLE>

Here's a bone for you. He said he was running 89 octane on a JDM D15B. (NOT 93 octane). Here are the stats of the engines he's running to refresh your memory:
D15B
VTEC
Found in:
1991-1999 Honda Civic VTi EG4 (Japanese Market)
1992-1998 Honda CRX VXi EG1 (Japanese Market)
Displacement : 1493 cm³
Bore and Stroke : 75 mm X 84.5 mm
Rod Length : 137 mm
Compression : 9.3:1
Power : 130 hp (97 kW) @ 5800 rpm & 102 ft·lbf (14.1kg/m) @ 5200 rpm
Redline : 7200 rpm
Fuel Cut : 7411 rpm
Valvetrain : SOHC VTEC
Head Code : P08
Fuel Control : OBD-1 MPFI

D15B (D15Z7) (with 3 stage VTEC)
3-stage VTEC
Found in:
1996-1999 Honda Civic VTi EK3 and Ferio Vi
Displacement : 1493 cm³
Bore and Stroke : 75 mm X 84.5 mm
Rod Length : 137 mm
Compression : 9.6:1
Power : 130 hp (97 kW) @ 7000 rpm & 102 ft·lbf (14.2kg/m) @ 5300 rpm
Valvetrain : SOHC VTEC
Fuel Control : OBD-2 MPFI

D16Y7
NON-VTEC
Found in:
1996-2000 Honda Civic DX/VP/LX/CX
1999 Honda Civic Special Edition - SE(Canada)
1996-97 Honda del Sol S
Displacement : 1593 cm³
Bore and Stroke : 75 mm X 90 mm
Compression : 9.4:1
Power : 106hp @ 6400 rpm
Torque (ft·lbf@rpm): 103 @ 4,600 rpm
RPM Redline : 6950 rpm
Valvetrain : SOHC 16 valves
Fuel Control : OBD2 MPFI
Head Code : P2F
Piston Code : P2E

Do you honestly think he shouldn't be running 89 octane on these engines? Especially considering we don't know what altitude he lives at or the ambient air temps when he's filling up. If you could do some tests I think you would find that putting 87 in these motors would not help his fuel efficiency *at all*. Not saying he couldn't, but it would not effect his efficiency. If you thought I was referring to the OP then you should have read my previous post where I told him he should be running 87 for sure. So do your homework before you start telling people their statements are not entirely true. That's all.

 

No. I don't think he should be running 89.

FYI, he nowhere indicated exactly what octane he was using in the civic, he did say he uses 89 in some old ford truck. When people say Hi-test, I think 91 or 93 octane. Mid-grade=89.

9.6:1 isn't considered high octane anymore.

Hell, I run 87 in my 01 b18c1 motor. No knocking, no problems, and I get 32mpg.

Most new cars are 9:1 or higher octane. I've owned numerous cars with 9.5:1 octane where the owners manual specifically indicates to use 87 octane, or low test.

Second, NOWHERE does 83RS say he's got a JDM d15b. He states he has a SOHC 1.5, which is likely a non-vtec D15. So, again, even if it were a JDM D15b, he STILL doesn't need to run 93 or even 89 octane. Mortificationrock said he had a JDM d15b, not the OP.....so lets be sure when you "throw me a bone" you're talking referring to the same person the rest of us are.

Get serious here man. That's an econo engine. ****, they're ALL econo engines. I'd run 93 in maybe the b18c5 and H22a4 or whatever it is, at best, and of course the K series, but the rest of 'em, gimme a break. No D-block in stock form will EVER require any mid or high grade gas. It's not made to burn high test, that's why he's fouling out plugs, not due to oil, and his economy will improve because the lower octane has better potential energy than high octane.

The only thing high test is for is detonation reduction.......which is why high performance and high compression motors use it. I don't consider anything below say 10.2:1 "high compression" anymore, as everything is tuned so precisely and gasoline octane is relatively common between brands.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Artifactr &raquo;</TD></TR><TR><TD CLASS="quote">Here's a bone for you. He said he was running 89 octane on a JDM D15B. (NOT 93 octane). Here are the stats of the engines he's running to refresh your memory:
D15B
VTEC
Found in:
1991-1999 Honda Civic VTi EG4 (Japanese Market)
1992-1998 Honda CRX VXi EG1 (Japanese Market)
Displacement : 1493 cm³
Bore and Stroke : 75 mm X 84.5 mm
Rod Length : 137 mm
Compression : 9.3:1
Power : 130 hp (97 kW) @ 5800 rpm & 102 ft·lbf (14.1kg/m) @ 5200 rpm
Redline : 7200 rpm
Fuel Cut : 7411 rpm
Valvetrain : SOHC VTEC
Head Code : P08
Fuel Control : OBD-1 MPFI

D15B (D15Z7) (with 3 stage VTEC)
3-stage VTEC
Found in:
1996-1999 Honda Civic VTi EK3 and Ferio Vi
Displacement : 1493 cm³
Bore and Stroke : 75 mm X 84.5 mm
Rod Length : 137 mm
Compression : 9.6:1
Power : 130 hp (97 kW) @ 7000 rpm & 102 ft·lbf (14.2kg/m) @ 5300 rpm
Valvetrain : SOHC VTEC
Fuel Control : OBD-2 MPFI

D16Y7
NON-VTEC
Found in:
1996-2000 Honda Civic DX/VP/LX/CX
1999 Honda Civic Special Edition - SE(Canada)
1996-97 Honda del Sol S
Displacement : 1593 cm³
Bore and Stroke : 75 mm X 90 mm
Compression : 9.4:1
Power : 106hp @ 6400 rpm
Torque (ft·lbf@rpm): 103 @ 4,600 rpm
RPM Redline : 6950 rpm
Valvetrain : SOHC 16 valves
Fuel Control : OBD2 MPFI
Head Code : P2F
Piston Code : P2E

Do you honestly think he shouldn't be running 89 octane on these engines? Especially considering we don't know what altitude he lives at or the ambient air temps when he's filling up. If you could do some tests I think you would find that putting 87 in these motors would not help his fuel efficiency *at all*. Not saying he couldn't, but it would not effect his efficiency. If you thought I was referring to the OP then you should have read my previous post where I told him he should be running 87 for sure. So do your homework before you start telling people their statements are not entirely true. That's all. </TD></TR></TABLE>

Ok yeah I have the Vti version the D15B Vtec. I just had curiousity about the statement of 89 taking more to burn than 87. On my d16y8 I also put 89 which I wonder if its not smart. Now on the other hand I think my d15b should maybe run higher since in japan they don't have diffirent octane's right? Correct me if im wrong.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by mortificationrock &raquo;</TD></TR><TR><TD CLASS="quote">

Ok yeah I have the Vti version the D15B Vtec. I just had curiousity about the statement of 89 taking more to burn than 87. On my d16y8 I also put 89 which I wonder if its not smart. Now on the other hand I think my d15b should maybe run higher since in japan they don't have diffirent octane's right? Correct me if im wrong.</TD></TR></TABLE>

FYI:
U.S. octane ratings: (ron+mon)/2.
JDM octane ratings: ron

Japan's 98 octane is equivalent to our 93 octane. And I highly doubt Honda required the 98 RON for the d15b in Japan. Remember, Japan is more fuel conscious than we are here, smaller cars, more efficient and smaller engines....so why would they develop an econobox motor making, what, 90-100hp max, that required high octane? Makes no sense economically or from a business standpoint.

Run 87 octane. If you're on stock ignition timing, you'll have no problems, and you won't be fouling plugs.

Unless you're a b18c5 or k-series block, or unless you're HEAVILY modified with major ignition timing increases, there's NO REASON TO RUN HIGH TEST! It's just a waste of your money in more ways than just the fuel!

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by chimmike &raquo;</TD></TR><TR><TD CLASS="quote">No. I don't think he should be running 89.

FYI, he nowhere indicated exactly what octane he was using in the civic, he did say he uses 89 in some old ford truck. When people say Hi-test, I think 91 or 93 octane. Mid-grade=89.

9.6:1 isn't considered high octane anymore.

Hell, I run 87 in my 01 b18c1 motor. No knocking, no problems, and I get 32mpg.

Most new cars are 9:1 or higher octane. I've owned numerous cars with 9.5:1 octane where the owners manual specifically indicates to use 87 octane, or low test.

Second, NOWHERE does 83RS say he's got a JDM d15b. He states he has a SOHC 1.5, which is likely a non-vtec D15. So, again, even if it were a JDM D15b, he STILL doesn't need to run 93 or even 89 octane. Mortificationrock said he had a JDM d15b, not the OP.....so lets be sure when you "throw me a bone" you're talking referring to the same person the rest of us are.

Get serious here man. That's an econo engine. ****, they're ALL econo engines. I'd run 93 in maybe the b18c5 and H22a4 or whatever it is, at best, and of course the K series, but the rest of 'em, gimme a break. No D-block in stock form will EVER require any mid or high grade gas. It's not made to burn high test, that's why he's fouling out plugs, not due to oil, and his economy will improve because the lower octane has better potential energy than high octane.

The only thing high test is for is detonation reduction.......which is why high performance and high compression motors use it. I don't consider anything below say 10.2:1 "high compression" anymore, as everything is tuned so precisely and gasoline octane is relatively common between brands.</TD></TR></TABLE>

Please use your reading skills to completely read *all my posts before subjecting us to anymore of your assumptions. My first posts were directed at the OP, the post you quoted me on was *NOT* in response to the OP. Now stop talking. If you want to run 87 gas in your b18c then by all means do it. But not everyone here wants to run crap gas, and in the D15B scenario the change from 89 to 87 really won't improve efficiency at all and could possibly cause pinging under certain circumstances. It's really his choice. Now for the 83RS he definitely should not be running high octane, only 87. So at least we agree on something.

Also, stop mixing up Compression Ratio and octane in your posts or you are going to confuse people on here. The compression ratio is just a factor in determining what gas to run. And just because you don't consider 9.6:1 CR high anymore has nothing to do with what octane the engine can safely run. It depends on the design of the head and many other factors.