AlexFW

Hi dear members!

During last months, I noticed a high consumption on my 545i: something like 8 kml/20 mpg at 90 MPH.. Usually, historically, I got 10 kml/25 mpg.

Ok, I replaced final ratio (-7%), I have had winter tyres on and ski holder on the roof, but from 10 to 8 there is a lot of road imho.


Could the cause be old spark plugs? My car has 60k km/ 38k miles.

I read some topics about spark plugs replacement and seems you got a higher mileage with new plugs, so:

a) did you notice an higher mileage once replaced spark plugs?

b) did you notice a worst consumption with winter tyres compared to summer tyres?

Today I had a 2-300 km spin but forgot to check on the onboard computer.

Thanks in advance!

AlexFW

Mh, seems on 30k people nobody never changed spark plugs

PraiseTheLowered

i changed mine at 55k and didnt notice too much of a difference. The old ones were kind burned up though

mikael

I replaced my plugs at 155'000 kms (they had been in since 60'000 km) and did not see a marked difference. I think winter tires and especially roof rack increases the fuel consumption though.

BTW, are your consumption figures read-outs from the OBC or calculated fill-up to fill-up?

AlexFW

OBC... Now I have Pilot Sport2 again and next sunday I will pay attention to the consumption at 140 kmh and I will report

Performance are changed with summer tyres, so likely the culprit was the winter tyre.

jsal

Don't waste your time on Spark Plugs until 100k.....SKI RACK.... Wind resistance is a huge factor on MPG and goes up logrithmically with speed. At 90 MPH it will be a very big factor. I see this even on my SUV which is a tank. Tires will affect MPG as well as weight. Not sure of the impact of the final drive ratio change.

It sounds like you are basing your MPG on instantaneous readings? At best you can only determine based on averages over time and the same road. slight grades, wind, weight will all have an impact. But my guess is if you went back to your summer tires and took the ski rack off, you would be back to normal.

MRV99

One factor which you may want to consider is the weight of your 166 setup compared to your winter setup. I was very conscious about that when I made my purchase. I saw that the Pilot Alpine Sports were a few pounds lighter per tire compared the Dunlop M3's and if your winter rims are heavier than your summer setup that could make a big difference. I know on my old E53 I had a 17" winter setup and a 20" summer setup and the weight difference was about 8-9lbs per tire(summer set was heavier) and I got better gas mileage in the winter. Just a thought

mikael

I have found the OBC to not always be that accurate, real world figures are often quite a bit worse than what the computer shows...

As a curiosity, I just found this website where you can keep track of your car's real consumption and share it with others. You can also search for real-life figures by other users:
http://www.spritmonitor.de/en/

Then you can add a little icon in your signature that shows your current consumption, as I have in my signature below. Pretty cool! I haven't transferred my data there yet so there is no number in my icon, but I will. I have it all in an Excel file on my home computer.

skylolow

Your ski rack and just the cold is causing it. I notice in my 545i with the rack on and loaded up with skis and snowboards it dropped my MPG by a good 3-4MPG on the HWY and I'm driving in pretty flat terrain for the most part. So I could easily see driving in mountains that you could go down 5-8MPG quite eaisly.