[Carbon dude]

So I've recently updated my G20 320D to the most recent software download, July update I think. Now I normally get about 530 miles to a full tank and it normally shows a estimated 520 ish miles when full.

Since the update it now shows 470 miles and half a tank got me 200 miles with 220 miles left. I've not changed my driving style.

Has anyone else experienced this and is it possible for a software update to make the car less fuel efficient?

[Tam the Bam]

Originally Posted by Gary1985

So I've recently updated my G20 320D to the most recent software download, July update I think. Now I normally get about 530 miles to a full tank and it normally shows a estimated 520 ish miles when full.

Since the update it now shows 470 miles and half a tank got me 200 miles with 220 miles left. I've not changed my driving style.

Has anyone else experienced this and is it possible for a software update to make the car less fuel efficient?

Maybe not the update.... could be linked to the colder weather....

[Carbon dude]

Maybe, it's the first time having the car through winter.

[HighlandPete]

Originally Posted by Gary1985

Maybe, it's the first time having the car through winter.

My thinking as well.

~10% drop in mpg (in a diesel) is not unexpected in winter... particularly in Scotland with lower average temperatures.

Part of it will be the extra electrical load. Remember the auxiliary electric heater element is power hungry. Will show more on something like a 320d, compared to a 330d.

[Carbon dude]

Thanks for the replies folks

[Beemer5to3]

Originally Posted by Tam the Bam

Maybe not the update.... could be linked to the colder weather....

For sure - forecourts will have moved to winter spec diesel, which contains a different mix to prevent freezing. Doesn't take temperatures much below zero to start making diesel start to go gloopy. I noticed a 5/6 mpg deficit in winter on my 520d.

[jon0]

I updated my 330d xdrive the other day, 420miles range before update, and 300miles range after update. Very odd. Upon brimming the tank after the update I had 430miles range, whereas previously it was showing 530 range

[Beemer5to3]

Originally Posted by jon0

I updated my 330d xdrive the other day, 420miles range before update, and 300miles range after update. Very odd. Upon brimming the tank after the update I had 430miles range, whereas previously it was showing 530 range

It's because the update will have wiped your previous driving data no doubt. The range on fill up will show more if you've been averaging a higher MPG before you filled up, and the opposite with lower MPG. That's all it'll be.

[Carbon dude]

Originally Posted by Beemer5to3

It's because the update will have wiped your previous driving data no doubt. The range on fill up will show more if you've been averaging a higher MPG before you filled up, and the opposite with lower MPG. That's all it'll be.

A great answer, I think this might be it. I just filled up the other day and already it was showing about 15 miles more than my last fill.

[jon0]

Yep, think that could be the case. Only had the car a few weeks - year old one with every option (or at least 90%!).

[Carbon dude]

Update, that's 3 full tanks and averaging 450 miles now, since the update. That's down by about 90 miles before the remote software update, where I averaged about 540 miles.
Driving style hasn't changed. If it possible that the update has somehow increased my full consumption?

[paulockenden]

Time of year?

[HighlandPete]

Originally Posted by Gary1985

Update, that's 3 full tanks and averaging 450 miles now, since the update. That's down by about 90 miles before the remote software update, where I averaged about 540 miles.
Driving style hasn't changed. If it possible that the update has somehow increased my full consumption?

Is this calculated figures, or OBC readings?

If it is OBC, could simply be a software change where the tolerance is different.

I had that once on my E91, after a software update/rewrite. The mpg read a different average, (under read by over 5%). Calculated, on brimmed tanks, no difference than before.

There was the option to correct it, experimenting with the 'correction factor', but I never bothered.

Remember it is colder at the moment, so add that into the mix, as we've mentioned before.

[Axeman15]

Originally Posted by HighlandPete

Is this calculated figures, or OBC readings?

If it is OBC, could simply be a software change where the tolerance is different.

I had that once on my E91, after a software update/rewrite. The mpg read a different average, (under read by over 5%). Calculated, on brimmed tanks, no difference than before.

There was the option to correct it, experimenting with the 'correction factor', but I never bothered.

Remember it is colder at the moment, so add that into the mix, as we've mentioned before.

I agree with Pete, brimmed tanks is the best way of calculating actual MPG. As I use my car for work and claim business mileage, I have a record of every fill up.

Last December and January covering 2,584 miles - average 37.86mpg
This year November to January (thanks to lockdown) 2,626 miles - average 37.33mpg.

I also think it is colder this year and I am doing shorter trips but still only 0.5mpg difference.

I am quite happy with overall consumption given the type of car and spec it is.

[Tam the Bam]

As stated by others.... diesel cars in cold weather with short journeys see lower mpg than in warmer weather due to longer engine heat up times. I had a diesel 520d (2 cars) over 11 years and lower winter MPG was always the case. I’m sure you will see an improvement as we get into spring/summer.

As others have stated mileage between full (to the top) tank comparisons is the way to get accurate figures.

[Carbon dude]

Thanks for the advice folks. I always take note of my millage once I fill up from empty and when I refill. From this, I work out how many miles I did on a full tank. That's were I've been getting my rough averages from before the update and now.

Just found it odd that once I installed the update I got lower milliage and quite a bit at that.

As you all said, I'll give it to the warmer months and see if there's a difference.

[Andy-1878]

I don't agree with the colder weather reasoning. I updated in the summer. I filled up, made a 150 mile journey and range stated 658 miles, 69.9mpg. Since the update after making that same journey after filling up its now range of 521 miles and mpg has dropped down as well. That was August, when it was nice and warm. Been into the garage who said the update hadn't installed properly. Still doing the same. Also, the range now drops or fluctuates a lot on short trips where it never used to. I can't remember the software it was on before, think it ended .54. But it's a hell of a drop and the only thing that's change is the software.

I can go to the gym, maybe a mile away at most. Loses up to 10 miles in range!

[HighlandPete]

Originally Posted by Andy-1878

I don't agree with the colder weather reasoning. I updated in the summer. I filled up, made a 150 mile journey and range stated 658 miles, 69.9mpg. Since the update after making that same journey after filling up its now range of 521 miles and mpg has dropped down as well. That was August, when it was nice and warm. Been into the garage who said the update hadn't installed properly. Still doing the same. Also, the range now drops or fluctuates a lot on short trips where it never used to. I can't remember the software it was on before, think it ended .54. But it's a hell of a drop and the only thing that's change is the software.

I can go to the gym, maybe a mile away at most. Loses up to 10 miles in range!

What was the software update for?

Like previous posts, are you actually calculating the brimmed consumption? Have you previous 'accurate' points of reference?

The range figure is a rolling calculation, so it is possible to see the sort of losses you notice on a cold 'mile' trip. How much it drops depends on how much fuel in the tank at the time. Logically (and in reality) nearly full tanks have bigger range variables, than when nearly empty.

[Andy-1878]

Originally Posted by HighlandPete

What was the software update for?

Like previous posts, are you actually calculating the brimmed consumption? Have you previous 'accurate' points of reference?

The range figure is a rolling calculation, so it is possible to see the sort of losses you notice on a cold 'mile' trip. How much it drops depends on how much fuel in the tank at the time. Logically (and in reality) nearly full tanks have bigger range variables, than when nearly empty.

I don't know what the update was for. It was just the OTA updates. Kept coming up with notifications to say there were new ones.

I make the same trip each month and usually when I do I've brimmed the tank before setting off. Before the update, I'd never arrive with a range that didn't start with a 6**. Very occasionally it would be a 5, but more 585+.

So I'd have travelled approx 150miles, still with a range of 600+. Totting up the miles covered on those tanks, the stated range + miles covered added up would be within say 10/20 miles of actual miles covered. So I'd say was accurate. I also didn't have the fluctuating, or sharp drop in miles on shorter trips I've been seeing since.