4.8i Fuel Economy is HORRIBLE

[blondboinsd]

Originally Posted by B-Line

I have a Porsche Turbo that is quoted at getting 30mpg.
Yeah, maybe if "where's the beef" lady is driving it..

B

[chor]

I have the 18's and doesn't give me good mileage...

[cpiguy]

I've only had the car for 5 days and 250 miles, but after setting the MPG when picking it up, I've averaged 17MPG combo driving.

PS: I have 20"

[mrkbbd]

That's not too bad, I get combined (90% highways w/ CC) 16.3 in my 4.8is. I have reset the avg fuel economy while using cruise control and not changing speeds for about 7 miles, and the highest I got was ~19.5mpg.

[AzNMpower32]

Give the engine 15-20k miles to break-in and reach its best efficiency. I remember our X3 was getting about 16mpg in the beginning, and now its up to 20.5 usually, with higher-than-EPA-estimates on the highway.

[pm_belo]

Originally Posted by AzNMpower32

Give the engine 15-20k miles to break-in and reach its best efficiency. I remember our X3 was getting about 16mpg in the beginning, and now its up to 20.5 usually, with higher-than-EPA-estimates on the highway.

You can also check the tire pressure.
I quote www.carbibles.com :
Tyre pressure and gas-mileage.

For the first two years of our new life in America, I'd take our Subaru for its service, and it would come back with the tyres pumped up to 40psi. Each time, I'd check the door pillar sticker which informed me that they should be 32psi front and 28psi rear, and let the air out to get to those values. Eventually, seeing odd tyre wear and getting fed up of doing this, I asked one of the mechanics "why do you always over-inflate the tyres?" I got a very long and technical response which basically indicated that Subaru are one of the manufacturers who've never really adjusted their recommended tyre pressures in line with new technology. It seems that the numbers they put in their manuals and door stickers are a little out of date. I'm a bit of a skeptic so I researched this on the Internet in some of the Impreza forums and chat rooms and it turns out to be true. So I pumped up the tyres to 40psi front and rear, as the garage had been doing, and as my research indicated. The result, of course, is a much stiffer ride. But the odd tyre wear has gone, and my gas-mileage has changed from a meagre 15.7mpg (U.S) to a slightly more respectable 20.32 mpg (U.S). That's with mostly stop-start in-town driving. Compare that to the official quoted Subaru figures of 21mpg (city) and 27mpg (freeway) and you'll see that by changing the tyre pressures to not match the manual and door sticker, I've basically achieved their quoted figures.

So what does this prove? Well for one it proves that tyre pressure is absolutely linked to your car's economy. I can get an extra 50 miles between fill-ups now. It also proves that it's worth researching things if you think something is a little odd. It does also add weight to the above motto about not trusting forecourt pressure gauges. Imagine if you're underfilling your tyres because of a dodgy pressure gauge - not only is it dangerous, but it's costing you at the pump too.

[PhoenixM3]

I totally forgot about tire pressure. It is really cold here so I am guessing my pressure is probably a bit on the low side. I will check tomorrow and let everyone know.

[cimbro]

Anyone has the 17' tires winter in their x? And which is the pressure used?
I think it could be very important for the fuel consumption.

[xnsf]

tire pressure does have an effect on fuel comsumption.

[Boston X5 4.4]

Originally Posted by cimbro

Anyone has the 17' tires winter in their x? And which is the pressure used?
I think it could be very important for the fuel consumption.

I have 17" winters on my X (E53) at the moment (Dunlop Grandtrek) and I run 32psi all round. I have not seen any real difference in fuel savings between 17's and summer 19's. Of course the engine is running colder and less efficiently in the winter also.