Why Poor Gas mileage/1995 540i

[msj1925]

I am getting(what I think is) poor gas mileage on my 1995 540i. Approx 11 mpg in city traffic. I am not driving spirited(right now) to see if gas mileage improves.
I have changed the spark plugs(NGK), 2 new oxygen sensors, tire pressure is correct. Car idles perfect, has great power and runs like a dream except for the poor mpg. I know with the 8 cyl, I won't get 25 mpg, but 15-18 in city driving is what I'd expect.
What kind of mileage are you 540'ers getting?? If you all are getting approx the same(11 mpg), so be it.
If you are getting better than 11 mpg, what else could cause poor gas mileage.
There are no codes.
Would a different muffler help?
Thanks to all who reply.

[msj1925]

Forgot to mention, that I had new injectors put in, new bottom intake gasket,new front & rear gasket on intake. No vacuum leaks.

Thanks to all

[Scott Jackson]

Well, with my 3.91 M5 rear in my 540iA, I get about 17-18mpg highway and I don't know what my city mpg is. I'd expect around 12mpg though. And for anyone who's wondering, yes, I'm still planning the Ford V8 swap. It's getting closer but I just gotta have all the bases covered before diving into it.

[wool00]

Are you calculating mileage by using the standard gal divided by miles or your onboard computer. Get on the hiway, set cruise for 55 mph then check MPG on your computer (don't forget to reset it:S/R button)

[James]

Using the standard gallons divided by miles. The obc also shows 12 mpg.

After searching previous years posts regarding mpg on the 540i, I thought maybe mine was somewhat low. Many posted they were getting 15-18mpg in city driving.
I can live with 12 mpg, but thought if there was something that could be done to improve mpg, I'd do it(besides what I have already replaced).
Thanks to all that replied.

[Owarrior]

i would say you should check your plugs for signs of running rich, if no signs, HAVE FUN WITH IT LIKE THAT, if u see signs and check your fuel pressure regulator.

[scott]

[Dave K]

I'v averaged 17 since I bought the car in March (95 6sp)per the computer. I got 23-24 on 500 mile drive home when I picked it up.

[squenton]

Because the M60 engine (with its knock sensors) can adjust timing to compensate for knock...it can use any fuel with an octane rating from 87 AKI - 93 AKI. While many choose to go with the lower 87 AKI fuel (thinking they are saving money)...the downside of that decision is fewer miles per tank of gas and lower engine performance. Whereas using a higher octane fuel may cost from $2-$4 more per tank of gas...you get more miles from the tank of gas PLUS better engine performance.

For example, in the hypothetical scenario presented below...the cost of fuel per mile is identical...yet the lower octane fuel is providing less performance, and the higher octane fuel is providing enhanced performance:

* 87 AKI - $2.97 x 22 gallons (full tank) = $65.34 ~ 300 miles achieved per tank ($65.34/300 miles = 0.22 cents per mile)
* 91 AKI - $3.24 x 22 gallons (full tank) = $71.28 ~ 330 miles achieved per tank ($71.28/330 miles = 0.22 cents per mile)

In the hypothetical scenario above, if you can achieve just 30 more miles out of a tank of gas by using higher octane fuel...the cost savings is nill compared to using lower octane fuel. Which means that using lower octane fuel only results in reduced performance ...when for the same cost "per mile"...higher octane fuel will provide an enhanced driving performance.




Q
1995 525iT~~~~~~~~~~1997 740iL
Build Date: 11/95~~~~~~Build Date: 03/97
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[jahy3]

I get about 11.5 mpg all city driving in Seattle. All highway about 25 in my 530i automatic '94.