full tank hwy k`s same as full tank of city k`s

[pillzor]

what gives here? im getting roughly 360km per tank city driving OR highway driving , i just did 360 all highway at mostly 110 with cruise control on only too end up with the same economy as around the city stop starting and doing cold runs too the shop n back.....
ive been told too look at o2 sensors but my sparkplugs are not dirty at all , so what else could it be?

[ephect]

change ur o2 sensors.. u should see an instant improvement, i did, n so has most members thats changed em. how long have u had the car? any idea if they've been changed?

check ur error codes n see if there is anything else underlying that could help contribute..

[TrikkBen]

Mate I just ran out of fuel at 230kms... city driving.... be happy lol

[pillzor]

yeh everyones saying 02 sensors , however an indicator of ****ed 02 sensors is dirty black spark plugs and ive just done an oil change, new oil filter, new plugs and the plugs were clean.
other culprits could be tuned memcal possibly and extractors + exhaust ( so im told i thought these were supposed too help economy if not tromping ).
and why the hell would it be using the exact same ammount of petrol on the highway as it does around town.

[Stressball]

why the hell would it be using the exact same ammount of petrol on the highway as it does around town.

You sure your fuel gauge isn't buggered?

[pillzor]

You sure your fuel gauge isn't buggered?

i thought that aswell and was going too run it completly dry and see how many k`s i was at , bad idea tho dont want a ****ed fuel pump from crap at the bottom of the tank adding too costs.

[jokerflingo]

Hmmm, i filled up and went highway driving a few weeks ago with a shocking head wind and got 450km's and the other week i filled up and have so far gotten 200km around the city with a bit more then half a tank left.

I am heavy footed so i guess thats not too bad.
Matt

[pillzor]

do you have any mods joker? , also i just read youre manual so that would contribute too economy.

[woteva]

The best economy improvement I did was to get a 'greenfoam'. I am now getting around 430 to 440kms where before I was getting 350 to 360kms.

[shiftySLE]

Cruise doesn't save fuel, a lot of people admit that it actually uses more, reason being that if you are cruising, you dont stress to drop 3 or 4 k's over a slight crest, cruise always accelerates and keeps you at 100 or 120 or whatever you have it set at. Times that by 10 or 20 times over a long drive and it doesn't save fuel at all, just speeding tickets and the really hard task of keeping your foot on the accelerator.

[greenacc]

what have spark plugs got to do with O2 sensors ?
O2 sensors are downstream of the spark plugs so i think you are confused there buddy. ... Dirty plugs usually mean you are burning oil.
Hows your air filter and injectors ?

[seraphic06]

Try cleaning your MAF as well. It helped shave an extra couple of litres per 100km for me.

[Dan366757]

my vs calais v6 gets 9L-10L per 100k (630ks) i live round morisset way so it isnt exactly stop start but on a freeway i can get it down to somewhere between 7L-8L per 100k (800ks).

[pillzor]

what have spark plugs got to do with O2 sensors ?
O2 sensors are downstream of the spark plugs so i think you are confused there buddy. ... Dirty plugs usually mean you are burning oil.
Hows your air filter and injectors ?

o2 sensors tell my engine how much fuel too combust right? meaning if they are telling my engine use too much its going too be coming from the engine which is before the o2 sensors isnt it
air filter is a 1.5 month old lukey high flow , injectors i couldnt tell you i wouldnt know how too tell or where too start.

what i will be doing is o2 sensors anyway just so i know theyve been done and because i like too throw money around and next country trip ill chuck the stock memcal back in and see what difference it makes if the new o2 sensors dont help.

[pillzor]

my vs calais v6 gets 9L-10L per 100k (630ks) i live round morisset way so it isnt exactly stop start but on a freeway i can get it down to somewhere between 7L-8L per 100k (800ks).

what mods have you done?

[ephect]

a couple of things.

1. has ur economy been slowly degrading? or has it all of a sudden just dropped.

2. how long have u owned the car? how many kms have u done since u've owned the car. has the O2's been changed since u've had it? its not exactly 'throwing money around', its keeping it maintained and operating efficently.

3. u have a modified memcal. if ur that worried that its not the O2 sensors, throw ur stock memcal back in n run it for a week or 2. do some hwy driving verses city, n see if they differ litres per 100kms.. did this consumption occur round the same time? could be just dumping more fuel in from the tune n lean cruise not set properly. its a possibility

[greenfoam]

VS's should be awesome on fuel, stock they should make well over 600ks on a tank on the highway, maybe 700+. I'd be looking very hard for broken stuff if it was getting anything under 600

[pillzor]

even with all the mods greenfoam?

[Cheap6]

yeh everyones saying 02 sensors , however an indicator of ****ed 02 sensors is dirty black spark plugs and ive just done an oil change, new oil filter, new plugs and the plugs were clean.
other culprits could be tuned memcal possibly and extractors + exhaust ( so im told i thought these were supposed too help economy if not tromping ).
and why the hell would it be using the exact same ammount of petrol on the highway as it does around town.

If all the 'plugs are clean - light grey w' ULP - it increases the likelihood of it being something other than an engine fault. Perhaps a trans slipping, torque converter fault or torque converter clutch not locking up? Some of those can hurt economy more on highway than city. No fault codes? What is the condition of the auto. oil or is there any sign of "mud" (band or clutch material) on the trans. dipstick?

PCM should learn around mild mods - with working O2 sensors - but maybe there is a mismatch between the mods and the memcal?

Extractors can upset the O2 sensor readings over cast manifolds too (less so with heated sensors).

Setting aside the difference between highway and city, tyre pressures, a brake caliper or park brake dragging, wheel alignment, roof racks, lower diff gears without correction, sticking thermostat, even the absence of the plastic air dam under the radiator?

i thought that aswell and was going too run it completly dry and see how many k`s i was at , bad idea tho dont want a ****ed fuel pump from crap at the bottom of the tank adding too costs.

You will be able to accurately measure FC without running the tank dry if you use a full tank instead of an empty one as your reference i.e. fill the tank, clear the trip meter drive and measure the volume then required to refill over the distance covered. Comparing the volume required to refill with the gauge position prior will also give some indication of the gauge accuracy - it's likely to be a 60 (63) litre tank.

[pillzor]

If all the 'plugs are clean - light grey w' ULP - it increases the likelihood of it being something other than an engine fault. Perhaps a trans slipping, torque converter fault or torque converter clutch not locking up? Some of those can hurt economy more on highway than city. No fault codes? What is the condition of the auto. oil or is there any sign of "mud" (band or clutch material) on the trans. dipstick?

PCM should learn around mild mods - with working O2 sensors - but maybe there is a mismatch between the mods and the memcal?

Extractors can upset the O2 sensor readings over cast manifolds too (less so with heated sensors).

Setting aside the difference between highway and city, tyre pressures, a brake caliper or park brake dragging, wheel alignment, roof racks, lower diff gears without correction, sticking thermostat, even the absence of the plastic air dam under the radiator?



You will be able to accurately measure FC without running the tank dry if you use a full tank instead of an empty one as your reference i.e. fill the tank, clear the trip meter drive and measure the volume then required to refill over the distance covered. Comparing the volume required to refill with the gauge position prior will also give some indication of the gauge accuracy - it's likely to be a 60 (63) litre tank.

thanks for that very helpfull post , also with the highway drive i did have a pretty strong headwind on the way back , strong enough too make it hard too open the door when pulled over.... thats obviously a factor , but how much.

wheel balance and alignment hasnt been done since i just threw walkies on it , they have wider tyres on them than stock... pressure is at 36psi i allways check.
trans doesnt slip at all and is tuned (memcal ) too change up gears at higher speed/revs which will be a factor aswell but again once youre sitting on 110 that shouldnt be a factor
oil was fine in the trans last i checked, had some really tiny clusters of bubbles on the stick thats about it.

also i dont have a trip computer so ill have too do it with a calculator i guess, when petrol light comes on it usually costs around the $50 mark too fill so im guessing theres about 10-15 litres left when the light comes on.

[vrcalais5ltr]

i own a vr calais and i get 840-860kms out a tank highway driving and 450kms per tank round city driving and its a 5ltr v8. whys the 6s use so much petrol? and that highway driving was with cruise control on. i used just over a tank driving from brisbane to newcastle thats 940kms.

[jokerflingo]

i own a vr calais and i get 840-860kms out a tank highway driving and 450kms per tank round city driving and its a 5ltr v8. whys the 6s use so much petrol? and that highway driving was with cruise control on. i used just over a tank driving from brisbane to newcastle thats 940kms.

I find those figures hard to believe unless you drive it under 1500rpm 24/7

[vrcalais5ltr]

nope i dont flog the snot out of it but i drive it hard. and it is true

[pillzor]

hes probably got a bigger tank.

[vrcalais5ltr]

its got a 80ltr tank in it aint that standard in the commodores?