PeachParts Mercedes-Benz Forum - Using reserve light to check MPG

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Quote:

Originally Posted by vstech (Post 2657919)

wow. that's thick. how much preheating do you do with your fuel?

Not much pre heating in the tank, just enough to flow to the engine.

Quote:

Originally Posted by funola (Post 2658273)

On VO, the reserve light and fuel gauge reacts much slower than on diesel because of the viscoisty difference, even after drilling out the drain/fill hole in the sender to a bigger size. I may drill it out bigger to make it react faster. On mine, when the reserve light comes on, it stays on (this is on the highway, no sharp turns etc).

Just realized that when the light comes on, I probably will not be at a location where it is convenient to drain the tank.

Plan B:

On level ground, when tank is near reserve (light not on), slowly drain tank till reserve light comes on, then continue draining into another (empty) container and measure what comes out.

You could also check that in reverse: after draining, how much do you add to make it go out?

I'd have two five gallon buckets nearby. I believe I drained 6 gallons out and my reserve light was on.

Data: '83 300CD, functional gauge and light, some gunk on sender since the draining was before I did that.

I drilled out the drain/ fill hole on the fuel sender to 1/8" and it reacts much faster now. If I make a sharp turn, the fuel gauge needle moves in concert with the sloshing in the tank. The reserve light has been coming on consistently at 500 to 510 miles on the last few tanks. It came on again today when I was 3 miles from home so I was able to drain the remainng VO into a cubie and it was half filled.
Now I know when the reserve light comes on, I have a lttle more than 2.5 gallons left