My M30 uses 20.5L/100km (11.5 miles a gallon)

[F4Phantom]

The M30 has just one O2 sensor. It can be a bear to remove, however.

My '91 M30 gives me 20 mpg with a 50/50 mix of highway and city. Have you considered that you may be driving the ol' E34 as fast as an F4 ? On mine, the fuel consumption goes up significantly at 50 MPH versus 70 MPH.

Regards,
Adnan

Yeah I dont think so, I like to give it a good rpm range occasionally but it is mostly my wife driving local trips. She drives very easy. Also the previous owner kept huge logs and always averaged 12.5L. The only main change I have made is a new tranny but I cant imagine a new/rebuilt tranny could add fuel like this - or perhaps the new tranny needs to be worn in? and loosen up a bit, cause if it does then the 'driving with handbrake' idea could be actually happening through the tranny. Either way my 02 sensor (lamda) is getting replaced.

Some of these replys I am having a very hard time understanding, and its even harder to just accept them as jokes because they are not funny. I recon if your trying to be funny, because there are no facial expressions to detect you need to be extra funny or poeple like me become confused on so many levels!

[Qube]

That's absolutely horrid. With A/C on I get at worst 16L/100KM

[califblue]

The Big 6 as the M30 is so aptly called likes to Drink Petroleum products...16-18 MPH here with city/fwy driving and best is 23.8 MPG@ 80mph w/ cruse control

I always drive with A/C on

And compared to my Hot Rodded 1835cc VW THING w/ dual 44 Webbers this is an Ecno Box!

[mamilapon]

I think I will check my O2 sensor - thats the thing plugged into the exhaust right? I will also change my fuel filter and see where that leads me. One potential problem is that these figures are off the OBC. Could this be wrong? I have done some mental arithmetic and it does not seem to be out by much but I do remember a post where someone was talking about changing a figure used by the OBC to run in it's calculations.

I would't trust my OBC, each time I press consump, I crap my pants!!

[McWatters]

If anyone watches Myth busters you will know that infact, using ur AC and driving uses less gas then driving with ur windows down..



J.McWatters

[BillionPa]

but is that true on an E34 with a very efficient aerodynamic profile?

[ILoveMPower]

My average is 19.1mpg, with basically like ALL spirited highway miles

If anyone watches Myth busters you will know that infact, using ur AC and driving uses less gas then driving with ur windows down..



J.McWatters

I didn't know that, but I definitely prefer windows down over A/C.

[Nick.Hay]

Mine is quite high too...

about 19L/100km

[Ausmpower]

No one has mentioned the temp sensor used for the DME, if it's faulty you'll constantly run rich (DME thinks the engine is cold and runs open loop).

I'd try O2 first then temp sensor-try one from a wrecker.

I get 13.6 L/100km to work and back stop-start no freeway and 9.8 l/100 constant 110kph highway (M30 535 manual).

[genphreak]

No one has mentioned the temp sensor used for the DME, if it's faulty you'll constantly run rich (DME thinks the engine is cold and runs open loop).

I'd try O2 first then temp sensor-try one from a wrecker.

I get 13.6 L/100km to work and back stop-start no freeway and 9.8 l/100 constant 110kph highway (M30 535 manual).

Yes, the book for an M30 auto e34 is like 16.9L/100km on the city cycle and 10.5L/100km at 120km highway cycle. Getting better is a matter of careful driving. My M30 used 20mpg before I changed the rotor cap and plugged the hole in the booster non-return valve (changed it actually but the 2mm hole only needed plugging). Maybe there was a leak in the intake too. Who knows. But I agree with what Joshua has said on this.

The biggest problem with factory M30 consumption is the city cycle. Big valved engine- great when you open her up but idling around she'll always use more than a vanos engine with smarter electronics like knock-sensing ECU and WBO2 sensors as Kristian said.

Good luck F4, let us know how you go w the O2 sensor. Nick