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.