Excessive gas consumption. Please help

[andrewwynn]

Run some Lucas fuel treatment through the had tank to clean injectors. Reset your fuel adaptations. Do you have a way to read your fuel trims and O2 readings?

With that low of mpg the mix has to be way off and should show up. I'm quite surprised no rich/lean code.

[SlickGT1]

So that you guys don’t cry too much. I drive mostly in NYC. My actual has always been about 1mpg lower than what computer shows. I get around 11mpg in the city. I have a real “go get it foot” and love how my exhaust rumbles. 4.8is, Worth it. Terrible mileage. But worth it.

Highways are completely different. If normal 70-90mph, I get over 20mpg.

If fuel prices bothered me more, I would switch to a Tesla. I’m not there yet.

[Pruzina]

Hi guy. Just quick update. Before I went to work I popped up the hood to check visually vacuum hoses and I found right the way one hose disconnected (U shape at the end close to dipstick) didn't have time look for more or find where it should go but definetly have to take a closer look what's going on over there.

Thank for tip with vacuum leaks tho. Maybe it's the light at the end of the tunnel

[Fifty150hs]

Originally Posted by Pruzina

Hi guy. Just quick update. Before I went to work I popped up the hood to check visually vacuum hoses and I found right the way one hose disconnected (U shape at the end close to dipstick) didn't have time look for more or find where it should go but definetly have to take a closer look what's going on over there.

Thank for tip with vacuum leaks tho. Maybe it's the light at the end of the tunnel

That's not a vacuum line. It's the breather from the front diff. Commonly mistaken for a disconnected vacuum line. It's rigid plastic, not a hose.

[Pruzina]

I'm almost 100% positive that it's a hose not a plastic tube. I'll take a picture in a few hrs

[Pruzina]

Fifty150hs I see you really know what are you talking about. You were absolutely right it's plastic tube exactly how you said.

I read in some treat that if you pull out the dipstick while idle it should change sound little bit as it's loose vacuum. Is it true? Bcs mine doesn't change at all.

[Fifty150hs]

Originally Posted by Pruzina

Fifty150hs I see you really know what are you talking about. You were absolutely right it's plastic tube exactly how you said.

I read in some treat that if you pull out the dipstick while idle it should change sound little bit as it's loose vacuum. Is it true? Bcs mine doesn't change at all.

I haven't heard of that test. The most definitive test I know of for a vacuum leak is a smoke test. Puts smoke into the intake system under pressure. Smoke will come out anywhere there is a leak. Another option is to take a can of carb cleaner spray and spray it around the intake system. If there's a leak, it will suck some of the spray in and the idle speed will change.

[bcredliner]

Mileage of even several vehicles that are exactly the same model, year, engine, using same source for fuel etc. will still vary in miles per gallon. Mileage of vehicles of different years, significant difference in mileage on the clock, no insight to upkeep, different geographic locations, temperature, humidity, source of fuel etc. may not even be in the ballpark to the mileage another is experiencing. Even method of calculation can result in a notable differences. However, usually the biggest variable is the driver's foot.

With our 4.6 mileage varies from 12.5 to 17.5. Low end is largely city stop and go driving with a fairly heavy foot but no full throttle and with some stints up to 60 for a few miles. 17.5 is no stops, constant speed driving at 70 on cruise control on a flat freeway when it is high humidity, in the low 60s with tires 3-5 pounds overinflated and attempting to maximize mileage. I always use Chevron fuel when available or a name brand fuel with a cleaning additive when not. Using the meth injection system improves mileage on average 2 MPG.

The factory rated mileage for a 2002 x5 3.0 is 14 city, 19 highway and 16 combined. That is with factory installed tires properly inflated. I don't know if things that would make a difference like the engine HP, TQ, transmission, or final drive ratios are different on earlier or later years.

I think it is a good idea to check mileage at least every few tanks. If it is down it can be foreshadowing or simple troubleshooting indication of something wrong.