[usedbimmer]

At 143000 miles I got a complete tuneup: valve cover gaskets, intakes new plugs. The car drives 1000 % better. In fact it drives tricking incredible! But gas mileage is no better than it was before. About 15 in town. About 17.5 on highway. I verified the accuracy of the trip mileage computer and it's dead accurate.

Also put in a quart of bgk44.

Any recommendations or is this just typical gas mileage for these brutes?

 

[02540ico]

Dirty air filter? When were the upstream O2 sensors replaced? If she's an auto, you sure you're getting 5th gear?
I get 17-or-so city, and 24-25 cruising at 70 hwy, and I know its time for O2 sensors with 101K on the clock. At 70mph, she's turning about 2350rpm.

 

[Al's540i]

+1 on the O2 sensors. Also, switch to Shell V-Power Premium gas. It works miracles. I get 26-28MGP highway now.

 

[andyffer]

+1 on the O2 sensors. Also, switch to Shell V-Power Premium gas. It works miracles. I get 26-28MGP highway now.

interesting sig! M5 gauge faces?

 

[02540ico]

+1 on the O2 sensors. Also, switch to Shell V-Power Premium gas. It works miracles. I get 26-28MGP highway now.

Do you get 26-28 with any fuel used now, or just when running the V-Power? Just wondering if the V-Power detergents cleaned out the fuel system to run more efficiently, or if the V-Power is just a better blend.

 

[Al's540i]

Do you get 26-28 with any fuel used now, or just when running the V-Power? Just wondering if the V-Power detergents cleaned out the fuel system to run more efficiently, or if the V-Power is just a better blend.

I get 26-28 MPG highway when running on Shell V-Power Premium WITHOUT ETHANOL.

If I happen to fill up with Shell that has 10% Ethanol then I get about 24-26 MPG highway.

 

[hts]

i've gotten 18.8 for the entire 9k miles since i bought mine last nov with 90% suburban/10% highway. i recently completed a roughly 300 mile (almost all) hwy trip and got 26.2. i couldn't believe it. i asked my wife when i got hom "so i've got a 7 year old car, built in 9/02, with a 4.4L V-8 and 290hp and guess what mileage i just got?"

:thumbup:

hard to believe this beautiful beast could get 26 mpg, even on the hwy!

 

[usedbimmer]

The o2 sensors makes sense. Type of gas makes no difference at all. Personally, I believe gas octane is way overrated. I've experimented with different octanes on all my cars I've ever owned and difference in performance at all not mpg. In fact I had a 2005 Pontiac g6 that did slightly better with 85.

 

[E39Freak]

+1 on the O2 sensors. Also, switch to Shell V-Power Premium gas. It works miracles. I get 26-28MGP highway now.

In addition to Shell, I've had good results with Chevron with Techron as well.

 

[atrovarious]

Wheel bearing can help.... Cost if you do all 4 yourself is around $350

 

[02540ico]

Wheel bearing can help.... Cost if you do all 4 yourself is around $350

Huh???

 

[chong188]

I dont think thats too bad of mileage. I often get 16-17 mpg city.Im Not too hard on the gas, maybe a few redlines on empty freeway merges a day.

 

[POof540i]

Yup. You just might be looking at its average gas consumption. I get 17.5mpg, 60/40 city highway driving. 14-16 strictly street, 25-26 strictly highway. Replacing the MAF, O2 sensors, and fuel filter would be a good idea at your mileage if they haven't been changed before, but I don't think it'll give you more than 1 or 2 mpg better overall. Everybody with a 540 seems to get great highway mpg, but less get great/good city mpg. Like me!

P.S. What kind of oil are you using?

 

[bowtie]

If the computer is anywhere close I'm getting low 30's at 65mph on trips...

 

[540 M-Sport]

Yup. You just might be looking at its average gas consumption. I get 17.5mpg, 60/40 city highway driving. 14-16 strictly street, 25-26 strictly highway. Replacing the MAF, O2 sensors, and fuel filter would be a good idea at your mileage if they haven't been changed before, but I don't think it'll give you more than 1 or 2 mpg better overall. Everybody with a 540 seems to get great highway mpg, but less get great/good city mpg. Like me!

P.S. What kind of oil are you using?

+1 on those mileage figures. I am not so sure on the O2 sensors, but you can buy software to check and graph their output to know for sure if they need replacing. If you want to just go ahead, you only need to do the pre-cat O2 sensors. Part #11-78-1-247-406 There are only $64 each with free shipping from RM European. I replaced mine at 115k miles and had no change in mileage.

Along with the fuel filter, one other thing to consider with our crappy gas, is that the injectors need to be removed and get a proper cleaning and calibrating.