Reserve fuel tank, when is fuel drawn from it?

philharve

Senior Member
Joined
Jan 20, 2005
Messages
1,773
Reaction score
5
Age
73
Location
Falmouth, Cornwall, United Kingdom
Website
go.to
Your Mercedes
W202 C230K Auto 2000
I recently purchased a 2000 (W) C230 Kompressor Sport saloon with a 62L+7L fuel tank. Today I filled it for the first time after purchasing it last week. I put in 58L because the fuel gauge was indicating less than a quarter of a tank remaining and the yellow warning indicator (low fuel) was illuminated.

If 58L of fuel went into a tank capable of holding 69L and the reserve is 7L, does this mean that fuel is drawn from the reserve only when the fuel gauge reads 'zero'?

By my reconning there is 4L of fuel that needs to be accounted for (58L+4L+7L=69L). That's almost a gallon and worth another 20 to 30 miles.

I suppose what I am inquiring about is 'does the yellow indicator mean that fuel is being drawn from the reserve OR does it mean the main tank is almost empty and fuel will soon be drawn from the reserve?'

I am making this inquiring because I am trying to determine what range I can expect on a full tank of petrol assuming I mainly use the M-B for travel between home and work, a round trip of 40 miles per day.

My previous car, a Toyota Celica GTI (1987 model), managed 300 miles (tops) between fill ups. The M-B is presently showing it is capable of bettering my old car with a range nearer the 350 mile mark. That's impressive given the superior performance of the M-B. I would have thought that the Rootes supercharger and being an automatic would mean a much poorer fuel consumption. I am pleasently surprised and will analyse fuel consumption over the coming months to get a more accurate estimate of overall range and fuel consumption.

On a long drive the M-B could return a considerably higher figure. So owning an M-B need not break the bank if you get a good one and look after it.

My Celica died after 170,000+ miles with suspected big end bearing failure. The body was beginning to suffer from rust so I wrote her off. I am hoping the M-B will be just as reliable and much longer lived. Thank you Toyota. Beat that M-B!

REGARDS Phil
 

joe bloggs

Senior Member
Joined
Jan 22, 2003
Messages
279
Reaction score
0
There is no reserve tank, the lamp just comes on when the level drops to a predetermined point, the guage cannot read to the bottom of the tank, i.e. it cannot guage all the fuel in the tank hence your discrepency.
 

jberks

Senior Member
Joined
May 12, 2004
Messages
11,153
Reaction score
41
Location
M1, Outside lane, somewhere between Leeds and Lond
Your Mercedes
Jaguar XF 3.0 S, LR Freelander 2, Fiat 500 & Fiat Panda
If you have the nerve, it's quite possible to drive the car some distance with needle under empty, the light on and the trip computer showing a range of 0 miles. Did this taking an Audi I was trading in. Its not good for the nerves though and you risk pulling crap through from the tank if you run to empty. I alway try to fill up just before the light comes on.
 

Myros

Senior Member
Joined
Aug 16, 2004
Messages
2,741
Reaction score
22
Location
in the great , grim 'oop north
Your Mercedes
R107, S211, R170, C219
nerves of steel

I decided to ignore my own advice and soldier on past the first flush of the yellow lght. I got about 45 miles out of the 7l reserve ( in theory about another 20 to go) when the big hill heading west from Brighouse on the M62 claimed me for a victim. The engine started sucking air and bucked and jerked the car for about 500m until I got it onto the hard shoulder. If you're going to fathom the depths of your tank, do it on the level where you have a fighting chance. Or better still, don't do it at all.
 
OP
philharve

philharve

Senior Member
Joined
Jan 20, 2005
Messages
1,773
Reaction score
5
Age
73
Location
Falmouth, Cornwall, United Kingdom
Website
go.to
Your Mercedes
W202 C230K Auto 2000
  • Thread Starter
  • Thread starter
  • #5
Update on my fuel consumption

Thanks All

I'm half way through my second tank of petrol in my C230 Kompressor (W reg.) and the odometer is reading 220 miles. If the fuel gauge is linear then I should achieve around 400 miles before refilling. My initial analysis (first tank of fuel) was >350 miles between fill ups. I will be very happy if I can achieve near the 400 figure because this will have been obtained largely through daily 40 mile round trips to work. On a long journey I would expect even better fuel efficiency. I am now monitoring engine oil comsumption.

No ... I'm not brave enough to risk running on empty until the fuel runs out. I could do that with my previous car, a 1987 Celica GTi, but I drove that car for 17 years and knew there was around 50 miles left in the tank once the fuel gauge read zero. I'm not risking that with the M-B, at least not yet. However, I did buy a green 10L fuel can last week, just in case.

As far as I can tell the yellow indicator in the fuel gauge illuminates when there is approximately 15% fuel remaining, which is quite a generous warning. I take your point about driving till empty and risking sludge being drawn though the fuel pipes. I will refill soon after the yellow indicator illuminates which should avoid any problems. I guess there is a fuel filter somewhere but without a workshop manual I'll have to rely upon my experience to locate it.

On the subject of manuals ... I've ordered some 'CD manuals' (eBay) because as far as I can tell there are no paper manuals supporting the Kompressor models. I have wondered whether the absence of manuals is a ploy to ensure owners take their cars to an M-B Service Station for servicing? Just a thought.

REGARDS Phil
 
OP
philharve

philharve

Senior Member
Joined
Jan 20, 2005
Messages
1,773
Reaction score
5
Age
73
Location
Falmouth, Cornwall, United Kingdom
Website
go.to
Your Mercedes
W202 C230K Auto 2000
  • Thread Starter
  • Thread starter
  • #6
Update on my fuel consumption

Hi All

I'm nearing the end of my second tank of fuel and if I believe my fuel gauge then I am averaging 100 miles per quarter tank of petrol giving a theoretical range of 400 miles per tank. The 'yellow' indicator should illuminate around the 350 mile mark indicating that I have at least another 50 mile range before I enter the 'unknown' region when the gauge reads '0'. I suspect there will still be at least one more gallon left in the tank when the gauge reads empty.

REGARDS Phil
 

Slaphead

Senior Member
Joined
Dec 24, 2004
Messages
99
Reaction score
1
Location
Dublin, Ireland.
I know your car is a reasonably fresh 2000 philharve but you still risk dragging God knows what out of your tank by letting it get so low... my MBs are significantly older (a '90 TE and '93 E) but I start looking around for a fill of petrol when the needle gets to the quarter full mark.... frankly if I do get the "Light of Doom" on the guage I'll pull into the next petrol ststion if only for ?10 to get me to a cheaper station....
 
OP
philharve

philharve

Senior Member
Joined
Jan 20, 2005
Messages
1,773
Reaction score
5
Age
73
Location
Falmouth, Cornwall, United Kingdom
Website
go.to
Your Mercedes
W202 C230K Auto 2000
  • Thread Starter
  • Thread starter
  • #8
Running near empty

Hi slaphead

Are you speaking from bitter experience? Have you ever (nearly) drained your car of fuel with adverse effects? It's your reference to 'Light of Doom' that I find interesting.

I have performed further analysis on my car's current fuel consumption and I reckon there is around 2 gallons of fuel remaining when the yellow indicator switches on.

I assume there is a fuel filter somewhere.

REGARDS Phil
 

pascal

Senior Member
Joined
Dec 28, 2004
Messages
1,636
Reaction score
3
Location
near Dublin
Your Mercedes
sl320/1999/3.2
The sender should activate the light when approx. 12.5% of its capacity is left. Well this is the standard for W124 & R129

W124 (except 500e):....... Total fuel: 70L ..... Reserve light: 9L
W124 (500E):................. Total fuel: 90L ..... Reserve light: 11.5L

R129:............................ Total fuel: 80L ..... Reserve light: 10L

So Phil, your figure of 2 gallons (9.09L) seems a bit risky. Calibration of the sender plays a factor also.

Pascal
 

Slaphead

Senior Member
Joined
Dec 24, 2004
Messages
99
Reaction score
1
Location
Dublin, Ireland.
philharve said:
Hi slaphead

Are you speaking from bitter experience? Have you ever (nearly) drained your car of fuel with adverse effects? It's your reference to 'Light of Doom' that I find interesting.

Not on a Merc but on an old Jap car I had years ago.... the kids were young so money was tight and filling up with petrol was always a last minute thing..... there was so much muck in the filters (I had fitted a second one just in case!) it was a wonder the thing drove at all.... without the filters the car would have been knackered completely. Wghich is why I hate to hear of people letting the tank run out or very low....
 

Avantgarde Automotive, Mercedes-Benz and SLR McLaren specialists. Service, repairs, diagnosis and motorsport preparation.
Unit 14 Hither Green Trading Estate, Clevedon, Somerset, BS21 6XU Tel: 01275 217270 Email:steve@avantgarde-automotive.co.uk
www.avantgarde-automotive.co.uk
Top Bottom