How to get better gas mileage for a 3rd gen

928 Views 40 Replies 11 Participants Last post by Sam91, 2 mo ago

Sam91

Discussion Starter · 2 mo ago

Ok guys so I have been driving my 1991 si alb to and from school for the past 2 weeks. I haven’t really been that happy with my gas mileage. So for this week I drove 4 days to school. The mileage is 7.8 miles to get there. After 4 days of driving a total of 15.6 miles a day my gas tank is down to half a tank. Should I be getting better mileage than that? At half a tank I have to refill it since it likes to die when braking. I am hoping to fix that this week. If my calculations are right I am getting around 10-12 mpg. And I am not even driving it hard. My car has 183,000 miles on it. What should I start replacing to get better mpg?

Thanks Sam

Also I can see the gas gauge move when I drive it. When I floor it I can definitely see it move.

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FirstCarNostalgic

· #2 · 2 mo ago

Here is a relevant post

http://prelude3g.com/p3g/frameset.htm

if you are actually getting 10-12 mpg that is very low. i would expect a leak somewhere. Do you smell gas in your oil? I’d check your fuel rail for visible leaks, and would send your injectors to be cleaned if you do smell gas in the oil.

otherwise you are running rich, or are driving the hell out of it lol.

Reactions: 1

1funryd

· #3 · 2 mo ago

Sam91 said:
Ok guys so I have been driving my 1991 si alb to and from school for the past 2 weeks. I haven’t really been that happy with my gas mileage. So for this week I drove 4 days to school. The mileage is 7.8 miles to get there. After 4 days of driving a total of 15.6 miles a day my gas tank is down to half a tank. Should I be getting better mileage than that? At half a tank I have to refill it since it likes to die when braking. I am hoping to fix that this week. If my calculations are right I am getting around 10-12 mpg. And I am not even driving it hard. My car has 183,000 miles on it. What should I start replacing to get better mpg?

Thanks Sam

Also I can see the gas gauge move when I drive it. When I floor it I can definitely see it move.

Source link: Gas Mileage of 1991 Honda Prelude

Here are the stats for your car:

Motor vehicle Vehicle Font Automotive tire Car

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Reactions: 2

Sam91

Discussion Starter · #4 · 2 mo ago

FirstCarNostalgic said:
Here is a relevant post

http://prelude3g.com/p3g/frameset.htm

if you are actually getting 10-12 mpg that is very low. i would expect a leak somewhere. Do you smell gas in your oil? I’d check your fuel rail for visible leaks, and would send your injectors to be cleaned if you do smell gas in the oil.

otherwise you are running rich, or are driving the hell out of it lol.

Umm when I click on the link it just goes to the home page of 3g prelude. I just figured it out and I am getting a little under 10 mpg. I actually haven’t smelled my oil. That is a good idea. But I know I am not burning any oil. I don’t see any leaks, just some oil leaks. Well It has been like 30-40 degrees outside so choke is one. Also my car when it starts up, it starts up at like 2,300 rpm. And it stays there for a while. But then once it warms up it idles down. I actually don’t drive it that hard. Usually when I accelerate harder I can literally see the gas gauge dropping. But when I came home today after getting a full tank of gas I full throttled it and the gas gauge didn’t drop at all. It seems when the gas tank is full it runs better.

Sam91

Discussion Starter · #5 · 2 mo ago

1funryd said:
Source link: Gas Mileage of 1991 Honda Prelude

Here are the stats for your car:

View attachment 33036

Yeah I am not getting that. I got like around 7 gallons for 68 miles.

1funryd

· #6 · 2 mo ago

Tune up time, more than likely your O2 sensor more than likely is not working properly.
Or
our timing is off and you are getting horrible gas mileage.

Reactions: 2

FirstCarNostalgic

· #7 · 2 mo ago

Here is the link — this one should work. I agree with Sean seems like tuneup time

www.preludepower.com

Bobnova's comprehensive guide to increasing fuel...

The second of my comprehensive guides. The first was a real compression check, this one is mileage. A n/a 3g prelude should be able to get between 28 and 35mpg, on combined city/highway driving. If it's all city, knock a couple mpg off that. If your getting 28mpg and want more, you can try my...

www.preludepower.com

www.preludepower.com

Reactions: 1

Sam91

Discussion Starter · #8 · 2 mo ago

1funryd said:
Tune up time, more than likely your O2 sensor more than likely is not working properly.
Or
our timing is off and you are getting horrible gas mileage.

But about 2 years ago they did spark plugs, wires, cap and rotor. Do you think it is already time to do that again? I don’t think they ever replaced the o2 sensor though. Do you guys have a preference for o2 sensors? Or will any parts store work?

Sam91

Discussion Starter · #9 · 2 mo ago

FirstCarNostalgic said:
Here is the link — this one should work. I agree with Sean seems like tuneup time

Bobnova's comprehensive guide to increasing fuel...

The second of my comprehensive guides. The first was a real compression check, this one is mileage. A n/a 3g prelude should be able to get between 28 and 35mpg, on combined city/highway driving. If it's all city, knock a couple mpg off that. If your getting 28mpg and want more, you can try my...

www.preludepower.com

Awesome! I also might replace my fuel filters maybe this weekend. I don’t think they have ever been replaced.

MustardCat

· #10 · 2 mo ago

Sam91 said:
But about 2 years ago they did spark plugs, wires, cap and rotor. Do you think it is already time to do that again? I don’t think they ever replaced the o2 sensor though. Do you guys have a preference for o2 sensors? Or will any parts store work?

They should still be fine.

---------

Are you calculating your mpg correctly? Don't use the gauge.

Fill up at your usual pump (until auto shut-off) and set your trip odometer to 0.
Drive normally a few days.
Fill up at the exact same pump (ideally).
Divide the trip odometer miles by how many gallons went in.
Example: 30 miles / 1.5 gallons = 20mpg

---------

Getting really bad mileage (with no visible leaks) is most likely going to be because of a sensor reading inaccurately. Most likely one of these:
O2 Sensor
Intake Air Temp (IAT)
Coolant Temperature Sensor (TW Sensor)

It's also possible an injector is stuck open or not not fully closing. Try pulling the spark plugs after driving for the day, if you you are running really rich they will be covered in black soot, if just one is covered in soot then that narrows it down.

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Reactions: 3

1funryd

· #11 · 2 mo ago

Check your plugs if they are black and not a light brown, then you are running rich, which is another indicator that O2 sensor is going bad.

If its wet, then the injectors are flooding the cylinder with fuel and not getting burnt up.
Go and check and get us pictures and results.

Reactions: 2

Sam91

Discussion Starter · #12 · 2 mo ago

3

MustardCat said:
They should still be fine.

---------

Are you calculating your mpg correctly? Don't use the gauge.

Fill up at your usual pump (until auto shut-off) and set your trip odometer to 0.
Drive normally a few days.
Fill up at the exact same pump (ideally).
Divide the trip odometer miles by how many gallons went in.
Example: 30 miles / 1.5 gallons = 20mpg

---------

Getting really bad mileage (with no visible leaks) is most likely going to be because of a sensor reading inaccurately. Most likely one of these:
O2 Sensor
Intake Air Temp (IAT)
Coolant Temperature Sensor (TW Sensor)

It's also possible an injector is stuck open or not not fully closing. Try pulling the spark plugs after driving for the day, if you you are running really rich they will be covered in black soot, if just one is covered in soot then that narrows it down.

What I did was go on google maps and figure out how many miles I drove. I will have to do the trip odometer. I am right around 68 miles of driving since the last fill up. I used 7 gallons in that time.

I think I am going to order fuel filters, and O2 sensor.

How do I check the other 2 sensors?

I just went out and checked the plugs even though I haven’t driven it yet today.

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Sam91

Discussion Starter · #13 · 2 mo ago

Where do you guys like to buy your O2 sensors from? Should I do Oriellys or rock auto. On Oriellys there are ones from $20-$70. Should I buy a cheap or expensive one?

Thanks Sam

FirstCarNostalgic

· #14 · 2 mo ago

Either store is fine. Car parts are mostly a you get what you pay for situation. The O2 sensor is one of the few parts you can still get an OEM replacement from Honda :

Honda 36531-PK3-A04

And for price reference it is $200.

I recently purchased one from Rock Auto. I think it was the NTK one and cost $30. Looks like they sell a Denso one which is a good brand as well for $40.
Id look at brand more than the price at first. That helps narrow down the choices. If a reputable brand makes the replacement part at X price, I wouldn’t spend more for the part unless I was getting an actual factory original.

typically I would have purchased the Honda one in this case, but with the amount of money I’m spending in initial restoration costs, I couldn’t justify the Honda part, especially since I’m not 100% sure what additional unexpected costs will pop up as I’m getting through the car.

if I were you I’d put a spreadsheet together of all the things you want to do to the car, and each item’s cost. That may help you decide how and where to allocate money. Being organized and deliberate with budgeting and spending has always helped me realize projects quicker—and make little decisions like which o2 sensor to buy a bit more straight forward.

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FirstCarNostalgic

· #15 · 2 mo ago

Sam91 said:
What I did was go on google maps and figure out how many miles I drove. I will have to do the trip odometer. I am right around 68 miles of driving since the last fill up. I used 7 gallons in that time.

I think I am going to order fuel filters, and O2 sensor.

How do I check the other 2 sensors?

I just went out and checked the plugs even though I haven’t driven it yet today. View attachment 33038
View attachment 33039
View attachment 33037

for as new as those look they do seem to be sooty, especially on the threads. I’d say looking at that you are running on the rich side.

Do you have a check engine light? Have you checked the ecu to see if it is showing any codes?

Reactions: 1

Sam91

Discussion Starter · #16 · 2 mo ago

FirstCarNostalgic said:
Either store is fine. Car parts are mostly a you get what you pay for situation. The O2 sensor is one of the few parts you can still get an OEM replacement from Honda :

Honda 36531-PK3-A04

And for price reference it is $200.

I recently purchased one from Rock Auto. I think it was the NTK one and cost $30. Looks like they sell a Denso one which is a good brand as well for $40.
Id look at brand more than the price at first. That helps narrow down the choices. If a reputable brand makes the replacement part at X price, I wouldn’t spend more for the part unless I was getting an actual factory original.

typically I would have purchased the Honda one in this case, but with the amount of money I’m spending in initial restoration costs, I couldn’t justify the Honda part, especially since I’m not 100% sure what additional unexpected costs will pop up as I’m getting through the car.

if I were you I’d put a spreadsheet together of all the things you want to do to the car, and each item’s cost. That may help you decide how and where to allocate money. Being organized and deliberate with budgeting and spending has always helped me realize projects quicker—and make little decisions like which o2 sensor to buy a bit more straight forward.

I am not going to spend $200. That is a little too much. Maybe if my lude had like 20,000 miles on it. Lol

Sam91

Discussion Starter · #17 · 2 mo ago

FirstCarNostalgic said:
for as new as those look they do seem to be sooty, especially on the threads. I’d say looking at that you are running on the rich side.

Do you have a check engine light? Have you checked the ecu to see if it is showing any codes?

Yea my grandpa says that usually when sensors start going out the engine runs rich so it doesn’t blow up.

I don’t have a check engine light. I haven’t checked the codes. How do you do that? I know you look through a window but how do I know what each code thing is for?

luzer

· #18 · 2 mo ago (Edited)

Sam91 said:
Yea my grandpa says that usually when sensors start going out the engine runs rich so it doesn’t blow up.

I don’t have a check engine light. I haven’t checked the codes. How do you do that? I know you look through a window but how do I know what each code thing is for?

Here you go Sam...

http://prelude3g.com/p3g/documentation/ecuerrorcodes/ecucodes.htm

Regarding o2 sensors, my only advice is to avoid Bosch sensors. I've always gone with NGK for o2 sensors as well as spark plugs.

Reactions: 1

Sam91

Discussion Starter · #19 · 2 mo ago

luzer said:
Here you go Sam...

http://prelude3g.com/p3g/documentation/ecuerrorcodes/ecucodes.htm

Thanks a bunch!

Reactions: 1

ulyssesmeads

· #20 · 2 mo ago

thanks

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