VY SS M6 Wagon Fuel Economy

[Brett SS]

Hey All,

My brother has a VY SS M6 wagon which has a twin 2.5" exhaust, OTR and mafless tune and the best he seems to be getting is about 13l/100km's (450km per tank) with mostly all highway work with only a little bit in and around a country town. Even on a complete highway run he can get closer to 12l/100km (500km per tank) but has never been below that.

He has standard 3.46 gears and usually drives on the highway in 5th gear as it drones a bit much for him in 6th. What sort of fuel economy are the other guys with wagons here getting? I've hooked up an AFR gauge and looked at his tune and it's fine but it still seems thirsty to me.

Also would changing from 3.46's to 3.91's make the fuel economy better all round or worse with the wagons?

Any help appreciated.

Brett.

[HRT 8]

Im guessing no headers Brett. IMHO all off the shelf catbacks drone on wagons.
As for the fuel usage, what afr's he running at cruise speeds? A decent amount of spark and an afr range of about 15.8 saw my old VY (cammed) run in the high 8's low 9's at highway speeds.
Tell him to do the headers and then use 6th.

[Brett SS]

Im guessing no headers Brett. IMHO all off the shelf catbacks drone on wagons.
As for the fuel usage, what afr's he running at cruise speeds? A decent amount of spark and an afr range of about 15.8 saw my old VY (cammed) run in the high 8's low 9's at highway speeds.
Tell him to do the headers and then use 6th.

Hey Grant,

Long time no see! At cruising speed with lean cruise on it's in the low 16's so it should be using less fuel than it is. Would changing to 3.91's make a difference also with the wagons? I assume it would make it better as my auto SV8 with 4.11's gets better economy on the highway than his wagon does at the moment.

How much spark were you running at cruise with your wagon? My brothers is around 28-30 at cruising speeds. I think he is still running the standard headers but I really didn't take too much notice with that. If you ask me the drone isn't bad at all so I've told them to just get used to it and use 6th. ;)

Brett.

[KeenGolfer]

Best I've done in mine is approx 650kms from a tank (south of Emerald in QLD to Townsville in 1 go) which I was very happy with. That's with a 6 litre with over 300 rwkw, 3.9's, and cruising in 6th at 100 kph most of the time.

[exwrx]

I got 780km out of a tank in 6th at highway speeds with 3.9 diff gears and a crappy maf tune. Even now with heads and cam I get in the 600's on the highway.

City driving is 18-21.

I would say failing to use 6th is really his problem.

[weekendwarrior]

mine as VZ six banger and im currently on an all new low of 13.8L/100km... At least it's down from the 16.2L/100km it was on a couple of weeks ago. And i spend the whole time driving this thing not getting about 2500rpm...

[Brett SS]

Thanks for the comments guys. Apart from using 6th all of the time will changing to 3.91's improve fuel economy also? I've seen it help with my auto's but was wondering whether going from 3.46's to 3.91's in his wagon is worth it.

Brett.

[HRT 8]

Its probably just as worthwile in a wagon Brett as a sedan. The extra weight might mean a bit more labouring with the 3.46's. I know it was well worth the effort in my old wagon. But I cannot comment if it made any diff to the fuel bills.