[MattX]

Hi all. Hoping you can help out with a UK 30D that I'm having a couple of issues with.

First is it wanders around. I got under the front and found multiple arms connecting it together. There's one in particular called, I believe, the radial arm and I could move it, freely a good few mm with my hand. Is that kaput and will it resolve the wandering if I replace both sides? Is it hard?
For refence, I did the front control arm bushes on an E46 - but it was a bugger of a job.

Second problem is MPG has fallen off a cliff in the last year. Had fresh oil early last year, only a few thou since correct 5w30 castrol. Put a brand new air filter in last week.
Average mid to low 30s whereas it was always mid to high 40s
I'm thinking thermostat. It gets up to the middle but it takes forever. Forever being 10+ minutes. Some casual net surfing makes me think the gauge isn't reliable and at TDC it may not actually be at that temp, and it should get up to temp fairly quickly?
MyE 46 M3 hits TDC on the gauge in a matter of minutes.

Any help appreciated

[Opie55]

You mention a gauge in conjunction with the thermostat. Unless your cars are different over there, you have no coolant gauge - that is an oil temp gauge. Is the logo on it a little oil can?

[Sandy5454]

Check the basics first- get your tracking and suspension checked, plenty of specialists out there.
Check the engine water temp using an OBDII reader- get one of eby or Amz. I use Bimmer link app on my phone. If necessary then change the thermostat.
Check your engine air cleaner? changed recently Or not?
Is you car smoky or hard to start? May need diesel injectors checked. DOnt just buy new ones unless you want to. Use good diesel eg Shell superdiesel until you have figured the problem out.

[Sandy5454]

Sorry I missed the fact you had changed your air filter already. Also cold temperature has a big impact on mPG. My MPG always drops in winter.

[fdpxfunix]

Sorry for bringing this thread back from the dead, but just mentioning recent observations of mine.

My 2018 30d’s (20k miles on the clock) mpg literally 'dropped off a cliff' on the 1st Oct. It was a wet horrible windy colder day here in the UK. I set off on the school run, left the car in Comfort, then chose ECO on the way back and was surprised at only getting 42mpg for the 17-mile round trip. The day before (a much nicer warmer 20oc day with lots of sun) even with a little Sport+ for a minute or 2 I got 47mpg. 47mpg is what I've been getting since I picked the car up in May regularly on the school run and at other times of the day too.

I've driven up to Manchester from West Sussex in the last month and broke the journey up with a night stop in Birmingham. Weather and traffic were good and temperatures around 14oc. The return journey from Birmingham to Manchester gave me 53.3mpg, which was mainly motorway driving and bit of Sports+ now and again. The highest I saw on the trip was 58.1mpg while stuck at 60mph with cruise control enabled for many many miles on the M6.

My 30d still seems amazing to me on longer runs regarding mpg, but local driving in the slightly colder UK weather and darker nights/mornings... it's not as good. This morning (same 17-mile round trip, Comfort, then ECO) I hit 40mpg in 3-4oc temperatures. The water temperature gauge didn't even get to its normal position until 9 miles. Back in the summer it was in this position by 3 or 4 miles

I still think even 40mpg is pretty good for a 3.0L lump with 620nm of torque, so not that bothered, but if mpg continues to drop even with me driving like Miss Daisy... I'll go see Mr BMW.


J.

[andreigbs]

First of all, you dieselheads need to be spending more time on the diesel subforum (https://f30.bimmerpost.com/forums/fo...play.php?f=488). Lots of interesting information there.

Secondly, fuel economy is dependent on many variables. Anything from outside temps, wind direction and speed, fuel quality and composition (many suppliers change formulas for winter vs other seasons), air pressures in the tyres, to engine oil and filters needing changing will directly (and indirectly) affect how much or how little fuel an engine burns.

If you've got a sticking thermostat which leads to longer warmup times, you'll be burning more fuel. If you've got thicker engine oil than needed/required, you're giving up some economy. Simply put, there are many factors that need to be taken into consideration. Parts wear out, including fuel pumps, turbos, and injectors. Sometimes it's a subtle change, other times it's quick and catastrophic.

It sounds like either tyres are not properly inflated and/or not properly wearing due to misalignment. I'd get that checked first. Then I'd try one or more fuel supplement/additives to see if increased cetane helps. In many cases, it should be plainly obvious.

All the best!