S14 mpg?

[S13..240sx]

Recently been having some gas issues in my 95 s14 and i was noticing it used a lot more gas than usual. So recently replaced spark plugs, o2 sensor, injectors and have dropped the tank to replace lines to ensure it was not the issue. drove the car 20 miles and it went from 3/4 to in between 3/4 and 1/2 so unsure if it is normal or i still have an ongoing problem.

[Thursday7]

Calculate MPG from fill up to fill up rather than analyzing a 30 year old analog gauge before making any assumptions and then report back.

If MPG is concerningly low after that, I would look into a fuel injector cleaning and replacing of O rings. Also check resistance on the coolant temp sensor.

[FaLKoN240]

The gas gauge/floater is probably rattled around in the tank if you dropped it.

I wouldn't go by that thing.

Get a full tank, reset the odometer.

Drive it until you need to refill again, divide the miles by the gallons you refilled.

Originally Posted by Thursday7

If MPG is concerningly low after that, I would look into a fuel injector cleaning and replacing of O rings. Also check resistance on the coolant temp sensor.

I echo this: Coolant temp sensor to ecu I would recommend replacing if you haven't done that already.

[silviaks2nr]

I also suspect that it's not a mileage issue. The fuel gauge drops consierably fast after it gets below 3/4. It is because of the tank design and where the level sender is.

[Kingtal0n]

What, you don't like getting 180 miles to the first half and 20 miles to the last half?

If you don't fill it all the way 10 gallons can come or go without moving the gauge

[S13..240sx]

Originally Posted by Thursday7

Calculate MPG from fill up to fill up rather than analyzing a 30 year old analog gauge before making any assumptions and then report back.

If MPG is concerningly low after that, I would look into a fuel injector cleaning and replacing of O rings. Also check resistance on the coolant temp sensor.

ill try the coolant temp sensor, mostly every thing has been released fueling wise. but i?ll give the sensor a shot. thank you

[S13..240sx]

Originally Posted by FaLKoN240

The gas gauge/floater is probably rattled around in the tank if you dropped it.

I wouldn't go by that thing.

Get a full tank, reset the odometer.

Drive it until you need to refill again, divide the miles by the gallons you refilled.



I echo this: Coolant temp sensor to ecu I would recommend replacing if you haven't done that already.

i verified that it was still on the hanger, but ill do the calculations and replace the cts and see how it goes

[S13..240sx]

Originally Posted by silviaks2nr

I also suspect that it's not a mileage issue. The fuel gauge drops consierably fast after it gets below 3/4. It is because of the tank design and where the level sender is.

noted thank you

[S13..240sx]

Originally Posted by Kingtal0n

What, you don't like getting 180 miles to the first half and 20 miles to the last half?

If you don't fill it all the way 10 gallons can come or go without moving the gauge

not the mpg im even getting to begin with, kinda why im asking because i would like to get around 180 but not the case even after replacing most fuel items

[Kingtal0n]

Factory 240sx should be around 25mpg with automatic
Iirc it could be 28 to 30mpg with 5-speed.

I used to get 33mpg with sr20det 5-speed.

It should not be less than 25mpg no matter what 4 or 6-cylinder at 2800lbs.
Even with a V8 240sx can 30mpg provided proper gear ratio and < 3000lbs.

In terms of tank mileage, its a ~15 gallon tank so at 25mpg (the minimum) it should do 250 miles to 10 gallons of fuel, 2/3 of the tank. I usually fill up with 3 or 4 gallons left so I average 260-280 miles per tank at 25mpg.

To get the mileage there are many factors, here are some
1. friction: tire pressure, alignment, wheel bearings, output, driveshaft and axles bearings/surfaces, no dragging brakes, E_brake isnt stuck on
2. air fuel ratio and cruise timing: 15.0:1 air fuel and proper cruise timing advanced typically 37-43*BTDC
3. healthy engine, good compression, clean fresh lightweight oil, no intake obstructions, no exhaust restrictions (bad cats clogged)
4. Lightweight vehicle (friction component from gravity) do not overload the vehicle with weight
5. Cruise RPM and engine load: Do not cruise outside of ideal engine efficiency range or where high wind resistance is a factor

[FaLKoN240]

Originally Posted by Kingtal0n

Factory 240sx should be around 25mpg with automatic
Iirc it could be 28 to 30mpg with 5-speed.

I used to get 33mpg with sr20det 5-speed.

It should not be less than 25mpg no matter what 4 or 6-cylinder at 2800lbs.
Even with a V8 240sx can 30mpg provided proper gear ratio and < 3000lbs.

In terms of tank mileage, its a ~15 gallon tank so at 25mpg (the minimum) it should do 250 miles to 10 gallons of fuel, 2/3 of the tank. I usually fill up with 3 or 4 gallons left so I average 260-280 miles per tank at 25mpg.

To get the mileage there are many factors, here are some
1. friction: tire pressure, alignment, wheel bearings, output, driveshaft and axles bearings/surfaces, no dragging brakes, E_brake isnt stuck on
2. air fuel ratio and cruise timing: 15.0:1 air fuel and proper cruise timing advanced typically 37-43*BTDC
3. healthy engine, good compression, clean fresh lightweight oil, no intake obstructions, no exhaust restrictions (bad cats clogged)
4. Lightweight vehicle (friction component from gravity) do not overload the vehicle with weight
5. Cruise RPM and engine load: Do not cruise outside of ideal engine efficiency range or where high wind resistance is a factor

IDK where you're getting those numbers from...



https://www.fueleconomy.gov/feg/bymo...an_240SX.shtml

[Kingtal0n]

Originally Posted by FaLKoN240

IDK where you're getting those numbers from...



https://www.fueleconomy.gov/feg/bymo...an_240SX.shtml

I measured it myself. I'm not sure why the posted mpg is so low. Those stock estimates are the mpg values I get with a 5.3L V8 + 4l80e 600rwhp with spirited driving and +300lbs. It's not accurately represented.

I've never seen a factory auto ka24de do less than 25mpg combined and I am pretty sure its 28 to 29mpg highway if the car is cruising maybe 65mph instead of 80mph. I never kept the ka very long though. The sr20 I have measured mpg far more often than the KA and I know for sure 30mpg is just a standard for the 5-speed swap. The lowest I ever recorded for sr20 was 25mpg combined and this was with an engine that had over 250,000 miles and 120psi of compression across the board.

Everytime I fill the tank to the top and record the mileage, add it to a spreadsheet, average, deviation, t-test, normal distribution. Check speedo accuracy.
My quoted numbers are scientific and accurate.

[Kingtal0n]

Original window sticker for S14 Automatic trans


Seems about right. I would see routinely 25mpg combined and like I said if you cruise control perfect 65mph it will 28mpg~ never 30 though.

[FaLKoN240]

Originally Posted by Kingtal0n

I measured it myself. I'm not sure why the posted mpg is so low. Those stock estimates are the mpg values I get with a 5.3L V8 + 4l80e 600rwhp with spirited driving and +300lbs. It's not accurately represented.

I've never seen a factory auto ka24de do less than 25mpg combined and I am pretty sure its 28 to 29mpg highway if the car is cruising maybe 65mph instead of 80mph. I never kept the ka very long though. The sr20 I have measured mpg far more often than the KA and I know for sure 30mpg is just a standard for the 5-speed swap. The lowest I ever recorded for sr20 was 25mpg combined and this was with an engine that had over 250,000 miles and 120psi of compression across the board.

Everytime I fill the tank to the top and record the mileage, add it to a spreadsheet, average, deviation, t-test, normal distribution. Check speedo accuracy.
My quoted numbers are scientific and accurate.

What you're describing is your anecdotal experience. I've gotten better than the EPA/manufacturer's rating myself.

However, factors like elevation, gas quality, etc are variables that can skew the final numbers. Manufacturers most likely use a secure facility to get these numbers out so they can give standardized results. To dealerships that will be selling these cars across the globe.

[OaxKouki]

Too much hypothetical talk here, this site shows you actual numbers from actual drivers. https://www.fuelly.com/car/nissan/240sx

[Kingtal0n]

Originally Posted by OaxKouki

Too much hypothetical talk here, this site shows you actual numbers from actual drivers. https://www.fuelly.com/car/nissan/240sx

First of all, we are actual drivers lol. Our data is as meaningful as anybody elses if its just random samples.


Next, that site is full is shit and people are not scientific when collecting their data. There is no way a 1990 240sx does better than 1998. It goes against everything we know about vehicles, technology, and time.


Finally, the number of people who input data to that site for the 97/98 models are similar in sample size to the number of 240sx I owned and collected data for. And I am an actual scientist, a doctor who has published papers with statistical inference, therefore I know my data methodology is superior to the random distribution of individuals who collected their mileage stats.