Omega Owners Forum

Omega Help Area => Omega General Help => Topic started by: martin341 on 02 December 2015, 17:24:05

Title: Fuel consumption
Post by: martin341 on 02 December 2015, 17:24:05
So looking for second opinion. Now as I've had the second miggy for a while i've noticed that the new 2,5v6 manual fuelconsumption is a bit bigger than in the 3,0v6 auto. The difference is biggest when engine is cold. Is it normal or should i check/fix something?

Cheers,
Martin
Title: Re: Fuel consumption
Post by: zirk on 02 December 2015, 17:39:43
When you say a bit bigger, do mean worse fuel economy, just checking as we tend to talk about number of miles per gallon (mpg) where as the rest of Euroloand talk about litres per kilometre (litres/100km), which is actually the other way around.


Title: Re: Fuel consumption
Post by: martin341 on 02 December 2015, 17:43:57
Yes, it uses more fuel than the 3,0 autobox car.
...and i drive them the same way...
Title: Re: Fuel consumption
Post by: zirk on 02 December 2015, 17:55:34
Assuming you have checked for fault codes, this times of year I would check working thermostat first for poor fuel consumption.
Title: Re: Fuel consumption
Post by: martin341 on 02 December 2015, 18:11:20
I'll try to read the COdes tomorrow. Paperclip. And the funny thing is that the thermostat is stuck open on 3,0 and seems to be working normal on 2,5 car
Title: Re: Fuel consumption
Post by: 05omegav6 on 02 December 2015, 18:13:13
Yes, it uses more fuel than the 3,0 autobox car.
...and i drive them the same way...
That be your issue then...

To make the 2.5 go anything like a 3.0 it will always use more fuel as it has less power and, importantly, less torque...

Put the other way, even driven really gently, the 3.0 will use less fuel than the 2.5... simply because it isn't really trying :y
Title: Re: Fuel consumption
Post by: zirk on 02 December 2015, 18:18:40
Swap the MAF's over.
Title: Re: Fuel consumption
Post by: martin341 on 02 December 2015, 18:57:07
Yes, it uses more fuel than the 3,0 autobox car.
...and i drive them the same way...
That be your issue then...

To make the 2.5 go anything like a 3.0 it will always use more fuel as it has less power and, importantly, less torque...

Put the other way, even driven really gently, the 3.0 will use less fuel than the 2.5... simply because it isn't really trying :y
I'm thinking the same thing but to be sure I asked you wise men for another opinion. And damn you can feel the power difference, at first i thought the 2,5 had some problems as it felt like my mom's 1,6 astra compared to 3,0 ;D
Title: Re: Fuel consumption
Post by: omega2018 on 02 December 2015, 23:34:59
don't have the 2.5/3.0 manual to hand, sure someone does, but:

Fuel consumption (ap prox . l/100 km) , CO2 em ission (approx. g/k m) , Saloon
Engine  Y 26 S E,  Y 32 S E
Manual/Automatic transmission
14.9/16. 4,  – /16. 8
Urban  8. 3/ 8.6,  – / 8. 9
Extra-urban  10.7/11. 5,  – /11. 8
Combined  257/ 276, – / 284
CO 2


manual (or auto) 2.6 beats a 3.2 for fuel consumption in all categories.
Title: Re: Fuel consumption
Post by: 05omegav6 on 02 December 2015, 23:38:13
Well there's a surprise... the smaller V6 auto uses almost the same amount of fuel as the larger one ;D
Title: Re: Fuel consumption
Post by: omega2018 on 02 December 2015, 23:45:13
performance figures here

http://www.parkers.co.uk/cars/reviews/facts-and-figures/vauxhall/omega/saloon-1994/ (http://www.parkers.co.uk/cars/reviews/facts-and-figures/vauxhall/omega/saloon-1994/)

2.5 manual 0-60 8.2 secs, 3.0 auto 0-60 9 secs.
Title: Re: Fuel consumption
Post by: dbug on 03 December 2015, 01:49:59
performance figures here

http://www.parkers.co.uk/cars/reviews/facts-and-figures/vauxhall/omega/saloon-1994/ (http://www.parkers.co.uk/cars/reviews/facts-and-figures/vauxhall/omega/saloon-1994/)

2.5 manual 0-60 8.2 secs, 3.0 auto 0-60 9 secs.

Would be sensible to quote like for like figures rather than try to "massage" figures -

2.5 manual 0-60 8.2 secs, 3.0 manual 0-60 8.0 secs
2.5 auto 0-60 9.2 secs, 3.0 auto 0-60 9.0 secs

same source, same models (Elites)
 ::)
 
Title: Re: Fuel consumption
Post by: omega2018 on 03 December 2015, 02:34:54
performance figures here

http://www.parkers.co.uk/cars/reviews/facts-and-figures/vauxhall/omega/saloon-1994/ (http://www.parkers.co.uk/cars/reviews/facts-and-figures/vauxhall/omega/saloon-1994/)

2.5 manual 0-60 8.2 secs, 3.0 auto 0-60 9 secs.

Would be sensible to quote like for like figures rather than try to "massage" figures -

2.5 manual 0-60 8.2 secs, 3.0 manual 0-60 8.0 secs
2.5 auto 0-60 9.2 secs, 3.0 auto 0-60 9.0 secs

same source, same models (Elites)
 ::)
 

op was asking about 3.0 auto compared to 2.5 manual ::)
Title: Re: Fuel consumption
Post by: Diamond Black Geezer on 03 December 2015, 10:44:07
OP - have a similar issue myself (though no 3.0 to compare it with, unlike yourself!  :))

Out of interest zirk, what will changing the MAF prove? Thought the MAFs weren't ever an issue on 2.5s always seeming bulletproof, only the later V6s for some reason seem to fail?

Check out my 'Stats' thread OP for some more info, if it helps  :)
Title: Re: Fuel consumption
Post by: martin341 on 03 December 2015, 17:10:02
...checked for fault codes....
Nothing but 31, so probably will do the stat in near future.
Title: Re: Fuel consumption
Post by: BazaJT on 03 December 2015, 18:33:55
Oh no!!!! Don't get Webby started on 0-60 times :D :D :D ;D
Title: Re: Fuel consumption
Post by: TheBoy on 03 December 2015, 18:48:59
I could post up over 5 yrs of data from my 3.0 auto, admittedly on LPG (so you'd need to add approx. 15%)
Title: Re: Fuel consumption
Post by: zirk on 03 December 2015, 20:13:26
OP - have a similar issue myself (though no 3.0 to compare it with, unlike yourself!  :))

Out of interest zirk, what will changing the MAF prove? Thought the MAFs weren't ever an issue on 2.5s always seeming bulletproof, only the later V6s for some reason seem to fail?

Check out my 'Stats' thread OP for some more info, if it helps  :)
It would prove its not a MAF problem, OP has almost like for like sitting on the drive so fairly easy to swop them over and see if the issue moves.

The MAF's don't always just fail, they can deteriorate over a time, feeding wrong info to the ECU.

 
Title: Re: Fuel consumption
Post by: TheBoy on 03 December 2015, 20:19:25
Generally, 2.5/3.0 MAFs either work, or are catastrophically wrong.  But there can always be exceptions, so if a spare exists on a convenient donor :y.


2.6/3.2 MAFs by comparison do tend to deteriorate rather than fail catastrophically.
Title: Re: Fuel consumption
Post by: terry paget on 04 December 2015, 07:55:22
My two 2.5CDX manual saloons give about 29.5mpg over 2000 miles of mixed driving, my 2.2 manual saloon only gave 27.0mpg over a similar mileage. As discussed on different thread, earlier engines are more efficient.
Title: Re: Fuel consumption
Post by: terry paget on 04 December 2015, 08:06:47
My two 2.5CDX manual saloons give about 29.5mpg over 2000 miles of mixed driving, my 2.2 manual saloon only gave 27.0mpg over a similar mileage. As discussed on different thread, earlier engines are more efficient.
Corection: the 2.5s are estates.
Title: Re: Fuel consumption
Post by: Diamond Black Geezer on 04 December 2015, 09:03:15
OP - have a similar issue myself (though no 3.0 to compare it with, unlike yourself!  :))

Out of interest zirk, what will changing the MAF prove? Thought the MAFs weren't ever an issue on 2.5s always seeming bulletproof, only the later V6s for some reason seem to fail?

Check out my 'Stats' thread OP for some more info, if it helps  :)
It would prove its not a MAF problem, OP has almost like for like sitting on the drive so fairly easy to swop them over and see if the issue moves.

The MAF's don't always just fail, they can deteriorate over a time, feeding wrong info to the ECU.

oh if its sitting there, well worth the 5 minute swap it is, agreed.  :y

Just checking if there'd be much point before I started to go hunting around for a spare MAF, that's all :). Worth it if you've already got a spare, though, quite agree.

Title: Re: Fuel consumption
Post by: zirk on 04 December 2015, 09:54:38
Strangely enough, Ive had 2 Maf's go, both on 3.0 MV6's, one gave up the ghost overnight and other was causing issues until I swapped it out.  I yet to have Maf go on a 2.6/3.2.:-\

Having said, Ive yet to have a Crank Sensor or Oil Cooler go on 3.0, they've all been on 2.6/3.2.   :-\ :-\