[ASHpro]

My SA told me " try not to run below 1/4 tank as it may negatively affect the engine performance and the turbos." I didn't understand how it would affect the turbos. Can someone shed some light on this?

[Ganxxta]

Turbos are cooled by oil, they are only connected by exhaust gases to fuel, so no fuel, no exhaust gases?

To be serious, IF the engine would run lean, it would mean higher temperatures inside the engine and turbo, which could harm the turbos, but to run lean because of low fuel, you must run on fumes already.
The engine will simply shut off before any engine parts can take damage.

1/4 tank is normally good for maybe 200km, its 15 liters of fuel.
I would start worrying at around 1 liter left in the tank.

[drexplode]

Originally Posted by Cloud9blue

All modern bmw has the fuel pump submerged in a fuel bucket that is suspended in the tank. Unless you are running the tank to the last liter of gas, the pump will always be surrounded and cooled by the gasoline around it in that bucket.

Love it when people posts up "facts" when they have no facts to back it up...

This. I work in the automotive industry as a fuel system engineer and fuel pump module (fuel bucket) is more or less standard due to low fuel handling. There are some non-traditional designs but they serve the same purpose...

https://www.google.com/search?q=fuel...V6chlBSdB5I%3D

[TrAcK TRaP]

every time my tank shows almost empty I get a misfire of low fuel misfire if I try to hit it hard :/

[Lups]

Yes mom, I will!

[Delta0311]

This is dedicated to all you guys living on the edge; one quarter tank at a time.

[gtaccord]

Just no...

[fiona01]

I likewise noticed should you generate on rates of speed under several fourths major velocity, having less pressure about the windows will cause it to crop up out ahead of time.

[bradleyland]

Originally Posted by BMWrules7

Technically, driving to E will use less gas than the guy (like me) who won't go below 1/2 tank:

Why?

Lighter car is more economical.

Ha! Touché!

[tc535i]

Originally Posted by fiona01

I likewise noticed should you generate on rates of speed under several fourths major velocity, having less pressure about the windows will cause it to crop up out ahead of time.

u wot m8

[bradleyland]

Originally Posted by tc535i

u wot m8

Fluid dynamics, bruh.

[....,,,,..,,..]

If your driving distance / style means you use a 1/4 tank in say 2 days, then yeah fill up regularly.

However, if like me you can get a week of driving out of a 1/4 tank, why hog around that extra weight of fuel?

With a previous car, we had to fill it to under half full, as a full tank would last over a month (60 mpg), so it routinely was well under 1/4 tank.

main things I have seen result in fuel pump problems are, crap fuel blocking filters and reducing flow, mods to cars that over pressurise the fuel pump, pressure relief valves breaking.

Remember when you are empty you still have 'reserve' amount of fuel. If the fuel pump just sat in the tank, then yeah it would get damaged with low fuel levels, however car manufacturers do cater this in to their designs and operations of parts.

[originalgoods13]

I run mine until fuel indicator tells me otherwise

[Efthreeoh]

Originally Posted by tc535i

these cars have a much better pump design than your average 70's chevy, if there's 1/4 gal left you can be sure it's in the pump basket. I was impressed when I pulled it out, much better engineering than my e36 and e46

Well most '70s Chevys had a mechanical fuel pump run off a cam lobe...

[Efthreeoh]

So I hired a Mexican (found him at the 7-11) to ride shotgun. When we come up on a gasoline truck, I have him jump out and grab the special-fitting hose I made to refuel my car "in-flight". Free gas and I never let the fuel pump over heat.

[YWGT3]

Spoke to a BMW SA who indicated that there is no exact hard and fast rule as to when to refill the gas tank other than what's been generalized in the vehicle's manual. However, he refills the tank around the remaining 1/4 level out of personal habit and because, at some point below the 1/4 tank level, the temp. for the residual gas starts to climb more rapidly as its liquid volume diminishes, thereby altering its performance characteristics as well as its ability to cool. Rather than trying to figure out where that threshold point is, he just refills at the 1/4 tank mark.

[RM7]

If you get to 1/4, you should put a few cups of water in there, to cool the pump.

[babyboss]

riding on almost Empty also causes airlock in tank so in time u will not have full range ..
advise from BP petroleum its best to fill up everytime u reach 1/2 ..

[pruettfan]

I don't believe this post to be factual. There is a fuel pump in the tank that pumps fuel up to the engine where there is a HPFP so there is not a set of circumstances where the system fails below 1/4 tank. If that is the case than at several points in my 204,000 miles with my E90 I should have had a fuel pump failure since I routinely run the car to about 1/8th of a tank before I fill it.

[pruettfan]

Originally Posted by yw

Spoke to a BMW SA who indicated that there is no exact hard and fast rule as to when to refill the gas tank other than what's been generalized in the vehicle's manual. However, he refills the tank around the remaining 1/4 level out of personal habit and because, at some point below the 1/4 tank level, the temp. for the residual gas starts to climb more rapidly as its liquid volume diminishes, thereby altering its performance characteristics as well as its ability to cool. Rather than trying to figure out where that threshold point is, he just refills at the 1/4 tank mark.

Not too many SA's have engineering credentials. Unless it is written by BMW in official documentation there is no reason to pay attention to this. The fact that the SA does x or y or z does not make it factually based.

[vachss]

I bought my 3.0si new from the dealer 8 years ago and have 150K miles on it now. With rare exceptions I've taken every damn tank down to ---. I ran out only once, early on while "calibrating" the gauge. Now I typically go 10-15 miles past --- and rarely get less than 400 miles on a tank.

Everything still runs fine. If I need to replace a fuel pump at 200K for my sins I'll deal.

[Delta0311]

Originally Posted by JamesNoBrakes

If you get to 1/4, you should put a few cups of water in there, to cool the pump.

Make sure to only use an ice cold bottle of Fiji spring water, this is a BMW after all.