bad gas mileage, bad MPG, High fuel consumption

[mcbit500]

It's all relative, my light foot still sees most cars rapidly disappearing in the rear view mirror albeit not nearly as quickly as happens with my heavy foot. I'm now driving a 25 mile round trip to work with about 90% on highway and am averaging around 11.5 - 12 mpg; on the same 170 mile roundtrip at 88ish mph as I used to do daily I still get the the same 14.5 mpg that I used to get with the 05 turbo and the 09 GTS. Go figure!

[gbratk]

In summer I drive in marina,where i have my boat, every weekend, doing 500miles on highway. I drive it gently all the time and best I get is 11mpg. Yesterday I drive it just a little bi more faster and I get 9,8 mpg.

I was already thinking to change fuel pumps, and I planning to change them soon, not to wait till they fail.

[ekstroemtj]

Reading your postings reminds me my situation in the past month. "driving issue at 3000 rpm" i tried to explain my problems. In the end the fuels pumps got changed and everything is fine. The car was running on bad pumps but you could feel it in performane and gas consumption that something was wrong. I take back the car from the shop last friday and since than i drove a lot. Highway and city driving. Performance great, consumption much better.

[mcbit500]

At 140kph on the highway I'd be expecting 15-16 l/100 km.

[ekstroemtj]

With not proper working fuel pumps i had 20 / 22

Liter per 100 km. Now much better. I need to check exactly

[gbratk]

With not proper working fuel pumps i had 20 / 22

Liter per 100 km. Now much better. I need to check exactly

This consumption is just like mine. Did you also see high consumption on PCM trip computer or just when you math?

I'll really change my fuel pumps. They will gone bad sooner or later, so it's better to change them now.

[ekstroemtj]

I read it on display and i feel it in my wallet . And the guy on fuel station was very friendly because i came twice per week:-)

[Bansasn]

In the high way I don't look at the mph. I look at my rpm and maintain it at 2000rpm. I get 16-18mpg every time.

[gbratk]

Fuel pumps are on the way. I'll change them next week, I hope there will be any difference in behavior, and consumption.

[clarksongli]

can someone explain to me how bad fuel pumps cause increased fuel consumption? Is the failure mode that the pumps surges randomly? We run a regulated return fuel system, so can't seem to understand why a pump would change fuel consumption

[gbratk]

Well fuel pumps are changed. It was definitely just the right time. Fuel filter was totally black like oil filter, and gas in filter housing was metallic black, so pumps where definitely on the way out. Now I'm wondering if could this metallic gas done some injury to injectors? Probably wont hurt to put some injector cleaner in tank.

I'll see if there will be some differences in behavior now.

[the head]

Keep us posted - mine has been awful as well.

[mplatt911]

My 04 Cayenne TT mileage has also degraded significantly. It has 150k miles on it. Just replaced a bad coil and all new NGK Iridium plugs. It starts and runs great. Still pulls like a freight train. We cannot seem to break 13mpg ever. It used to get close to 20mpg on highway and 16-18 on easy trips to town. I have Durametric software and all looks normal. No codes, etc. Any idea of what i should look for?

TIA

Mike

[ekstroemtj]

Just can repeat what i wrote before. After i got new fuel pumps the results improved in many ways. Engine feels more strong and the liters per km dropped a lot . I just made a trip to belgium, some hundred of kilometers highway driving. Average speed between 120 and 160 km/h. Fuel consumption is until now 13,7 liters per 100 km

[mcbit500]

Just can repeat what i wrote before. After i got new fuel pumps the results improved in many ways. Engine feels more strong and the liters per km dropped a lot . I just made a trip to belgium, some hundred of kilometers highway driving. Average speed between 120 and 160 km/h. Fuel consumption is until now 13,7 liters per 100 km

Is that computer or calculated? Its about what my computer says but its not what i get.

[ekstroemtj]

I would say both. I was driving about 700 km from one stop to next. But i need to calculate exactly

[mcbit500]

Same trip to work every day all highway at around 140kph in GTS (left) 05 turbo (right) last column is litres/100 km

Edited October 8, 2013 by mcbit500

[ekstroemtj]

Wow. You keep your books. I stopped this long time ago. This is a 2,6 tonn vehikel and i guess you cant bring it down more.

[mcbit500]

Fortunately i'm now down to about 270 kms per week instead of per day.

[gbratk]

It's been three weeks since I changed fuel pumps,but consumption remains the same. Trip computer say around 14l/100km but reality is 20l/100km.

[hcheun]

have you checked your bearings on your car? that's another reason, high drag on the tires could cause it as well. Also noticed if your tires are being eaten up quicker than often?

Definitely check those

[leporsche44]

On 10/9/2013 at 1:02 AM, gbratk said:

It's been three weeks since I changed fuel pumps,but consumption remains the same. Trip computer say around 14l/100km but reality is 20l/100km.

I know this post is old but were you able to find out what the problem was?? I have a 2010 GTS it runs great but the gas mileage SUCKS!!!