List of Factors for Fuel Consumption

[Mordan]

Hello..

I'm trying to list factors of increasing fuel consumption in old cars.
what are from your hands on experience DIY jobs that decreased/increased the consumption.

I would divide increased consumption into 3 categories

1) engine wear and engine tuning which leads to less power and more fuel consumed
worn piston rings, wrong valve clearances, fouled spark plugs,

2)fuel injection problem
old injectors don't vaporize the fuel as well anymore (will new ones really improve the fuel consumption?)

3) body factors
tyres balance and size, sway bar links, holes in the exhaust, too much weigh in the car (of course)

will the lack of fuel pressure be an issue? (fuel pressure regulator and fuel pump)

I'm reading somewhere ignition coil may increase consumption.... how?


thx

[Jehu]

I just bought new 02 sensors thinming my MPG would rise to where it seemed to be when I first bought the car... reports since have suggested I may have been under a false impression we'll see though.. I drive the car virtually daily. even when I;m not driving it for work I take it out onto the local highway for a few miles to operating temp and get it all lubed up.. whenI forst bought it seemd to get up around 23-25 highway now I'm lucky if it stays at 19... when I leave both calculations alone and am driving mixed highway/city it reads between 15 and 17... It is time to change spark plugs but fuel filters get changed regularly .. I am in the gate to have a major overhaul done on the engine to fix an oil leak so it will have new intake gaskets, plugs and coil boots then as well as the new 02 sensors I'll report the results.

[Tiger]

Lack of fuel pressure will cause poor atomization in fuel injector

Bad ignition coil will cause poor spark and poor combustion. Alot of time it is the boot that is the issue... factory boot was not good at insulating so weaker spark get to the spark plug. Not only that... computer uses the spark signature to determine how to adjust the timing... so lots of factors here.

Bigger tires tends to lose 1 MPG.

Poor engine? Hard to believe on German engine... simple thing like if you have M20 or M30 engine that needs periodic valve adjustment... but other engines... not really an issue. Synthetic oil will reduce consumption.

Biggest fuel economy improvement is your body condition... if oxidized... feels like sandpaper... will affect aerodynamic drag.

[Jehu]

Biggest fuel economy improvement is your body condition... if oxidized... feels like sandpaper... will affect aerodynamic drag.


Funny you say this.. I thought of adding above that I clearly noticed an increase in the measured MPG AFTER Waxing my car... I thought It was coincidence..

[repenttokyo]

clogged catalytic converters. clogged fuel filters.

[Tiger]

I have never seen a clogged fuel filter... have you?

[uscharalph]

Funny you say this.. I thought of adding above that I clearly noticed an increase in the measured MPG AFTER Waxing my car... I thought It was coincidence..
My car allways runs better after it's just been washed. Even better after fresh wax. LOL!!!!

[Kibokojoe]

Yes but not on my 535i

[repenttokyo]

I have never seen a clogged fuel filter... have you?

yes, and it leads to a lean condition and a lack of power, overevving to get more fuel, which leads to inefficient combustion and overconsumption.

[ryan roopnarine]

I have never seen a clogged fuel filter... have you?

hells yeah. the 99 taurus will jump 10 psi at the rail if the fuel filter is questionable. i think that for the filter to be an issue, the owner had to run it really low/out a couple of times which forces the crap to be picked up from the bottom. even if i don't let it run down, once every 6 months I change the filter, and it makes a big difference.

[Mordan]

hells yeah. the 99 taurus will jump 10 psi at the rail if the fuel filter is questionable. i think that for the filter to be an issue, the owner had to run it really low/out a couple of times which forces the crap to be picked up from the bottom. even if i don't let it run down, once every 6 months I change the filter, and it makes a big difference.

I thought the fuel filter was rarely in need to be changed compared to a diesel filter.

[Bill R.]

affect gas mileage, doesn't cause overrevving. With a plugged filter the car will idle fine, it will just starve for fuel under load , such as high speed. It will effectively limit the speed of a car.
The last really plugged one i saw was a toyota cressida that wouldn't go over 60mph, just not enough power to go faster. The filter was so plugged up you couldn't blow through it.

Ryan, think about it for a minute, the filter is long before the fuel rail,if the filter was plugged the pressure at the rail would drop rather than raise.
And the fuel pump pickup is always sucking the gas off of the bottom of the tank so anything on the bottom is getting sucked up all the time not when you run low or run out of fuel.

[Mordan]

by the way

does an old differential increase the fuel consumption?

[Bill R.]

O2 sensor frequently does improve gas mileage. I see it all the time.
A sensor thats old or bad reacts slower and often has larger sweeps when you graph the voltage of one. When you watch the o2 sensor on a graph its obvious which one is an old one and which one is new. And the old story of cleaning them out with a torch isn't true either. If in doubt replace it.

Other things to look at for fuel economy is the rolling resistance of the tires themselves, that can be a 5% variation in economy depending on the tire. Consumer reports typically lists the rolling resistance of any tire they test. A few other companies are starting to list the rolling resistance of each tire they make.

Making sure that none of the brakes drag even slightly will help improve mileage, If the calipers aren't retracting then the pads drag slightly and that adds up, Checking the differential oil and using the lightest grade that is acceptable will help, check CV's at the rear axle for any binding or drag, same with the wheel and axle bearings, make sure the center bearing on the driveshaft spins freely, make sure the emergency brake shoes retract and don't add to drag. Check tire pressures.

Fuel pressure , make sure the injectors are clean, plugs gapped correctly, temperature sensor functioning correctly, air filters clean, Don't forget that the 10% ethanol gas used in the winter in a lot of places causes mileage to drop 15 to 20% minimum.... and on and on.. Make sure the fan clutch is disengaging when not needed. Make sure the A/C compressor isn't turned on , On some cars a dirty maf will make it go lean off idle causing you to depress the gas more which hurts economy.

[Jehu]

O2 sensor frequently does improve gas mileage. I see it all the time.
A sensor thats old or bad reacts slower and often has larger sweeps when you graph the voltage of one. When you watch the o2 sensor on a graph its obvious which one is an old one and which one is new. And the old story of cleaning them out with a torch isn't true either. If in doubt replace it.

Other things to look at for fuel economy is the rolling resistance of the tires themselves, that can be a 5% variation in economy depending on the tire. Consumer reports typically lists the rolling resistance of any tire they test. A few other companies are starting to list the rolling resistance of each tire they make.

Making sure that none of the brakes drag even slightly will help improve mileage, If the calipers aren't retracting then the pads drag slightly and that adds up, Checking the differential oil and using the lightest grade that is acceptable will help, check CV's at the rear axle for any binding or drag, same with the wheel and axle bearings, make sure the center bearing on the driveshaft spins freely, make sure the emergency brake shoes retract and don't add to drag. Check tire pressures.

Fuel pressure , make sure the injectors are clean, plugs gapped correctly, temperature sensor functioning correctly, air filters clean, Don't forget that the 10% ethanol gas used in the winter in a lot of places causes mileage to drop 15 to 20% minimum.... and on and on.. Make sure the fan clutch is disengaging when not needed. Make sure the A/C compressor isn't turned on , On some cars a dirty maf will make it go lean off idle causing you to depress the gas more which hurts economy.


Do products like Lubro Moly's Jectron http://www.allzim.com/acatalog/LM2007.jpgor Lucas Oil's Fuel Injector cleanerhttp://www.sjmparts.com/images/051/051-587C.jpg work enough or are you tallking taking them out and cleaning then ?

[Bill R.]

gas tank is the BG44k, otherwise i've had ok results with seafoam and the otc injector cleaners on my on the car injector cleaner, which runs either straight concentrate or 50/50 depending on the brand of concentrate i'm using in the injector cleaner.

Some cars don't even respond to that and i end up pulling the injectors and having them cleaned or replace them with some off the net.

I ordered a set of the ford ones cleaned and flow tested for 45.00 on ebay, since i was stupid enough to let my fuel pump gunk up and the gas tank to rust up. I guessed that the injectors would be the same so i ordered a set and pulled them yesterday.






Do products like Lubro Moly's Jectron http://www.allzim.com/acatalog/LM2007.jpgor Lucas Oil's Fuel Injector cleanerhttp://www.sjmparts.com/images/051/051-587C.jpg work enough or are you tallking taking them out and cleaning then ?

[Mordan]

gas tank is the BG44k, otherwise i've had ok results with seafoam and the otc injector cleaners on my on the car injector cleaner, which runs either straight concentrate or 50/50 depending on the brand of concentrate i'm using in the injector cleaner.

Some cars don't even respond to that and i end up pulling the injectors and having them cleaned or replace them with some off the net.

I ordered a set of the ford ones cleaned and flow tested for 45.00 on ebay, since i was stupid enough to let my fuel pump gunk up and the gas tank to rust up. I guessed that the injectors would be the same so i ordered a set and pulled them yesterday.

in my search to improve fuel economy I found this polish product which reads like a miracle

http://www.ceramizer.com/content/view/36/43/

it is **** scaring if that works. after running 600km your engine compression are like new ??????!?!?!
it also have additive for the gear box and differential...
thx for the tips Bill about the CV and brakes... I will have to check that. I just jack the car and turn the wheels listening for noise?

[Bill R.]

is normal... which is hard to describe if you haven't spun a lot of wheels or axles unfortunately.
I wouldn't bank on that ceramizer working though....




in my search to improve fuel economy I found this polish product which reads like a miracle

http://www.ceramizer.com/content/view/36/43/

it is **** scaring if that works. after running 600km your engine compression are like new ??????!?!?!
it also have additive for the gear box and differential...
thx for the tips Bill about the CV and brakes... I will have to check that. I just jack the car and turn the wheels listening for noise?

[ryan roopnarine]

affect gas mileage, doesn't cause overrevving. With a plugged filter the car will idle fine, it will just starve for fuel under load , such as high speed. It will effectively limit the speed of a car.
The last really plugged one i saw was a toyota cressida that wouldn't go over 60mph, just not enough power to go faster. The filter was so plugged up you couldn't blow through it.

Ryan, think about it for a minute, the filter is long before the fuel rail,if the filter was plugged the pressure at the rail would drop rather than raise.
And the fuel pump pickup is always sucking the gas off of the bottom of the tank so anything on the bottom is getting sucked up all the time not when you run low or run out of fuel.


i didn't make myself clear about that. one day, when the car wasn't running for s@iat, i hooked up a fuel pressure gauge to the rail and saw that it was about ~20 something. a new fuel filter put it back to where it was supposed to be (iirc 30~ at the schrader). i know when it is going bad because the car will start to act in a pecuilar manner while cresting hills (and at the bottom). the bottom is actually where it starts sputtering almost imperceivably. i can't explain why a <20 year old car is choking on fuel filters, it isn't carburetted, but it does it, and the filter has resolved the problem every time.

[bsell]

i can't explain why a <20 year old car is choking on fuel filters, it isn't carburetted, but it does it, and the filter has resolved the problem every time.

What is in your tank that is trashing your filters? Or are you pumping the trash in from old gas station tanks?

It is probably time to take a look inside your gas tank to see what there is to see.

Brian

[repenttokyo]

What is in your tank that is trashing your filters? Or are you pumping the trash in from old gas station tanks?

It is probably time to take a look inside your gas tank to see what there is to see.

Brian

condensation inside a tank that is kept mostly empty during temperature fluctuations can lead to corrosion that ends up clogging filters and pumps.

[Mordan]

condensation inside a tank that is kept mostly empty during temperature fluctuations can lead to corrosion that ends up clogging filters and pumps.

good point for an old BMW with metal fuel tank

[repenttokyo]

good point for an old BMW with metal fuel tank

happened to me on an older mercedes :(