Quote:
Originally Posted by Yak
I'm trying to follow the process:
Fill up with VO*
Start mileage count on GPS
Drive till light comes on and record miles driven, hoping you catch it at that moment?
In practice my light comes and goes: left turn = light on, right turn = light off. Slight glow, then full bright later. It's not on/off.
Then assume 21.1-2.9 for consumption when the light is on steady? (you could sub whatever measured value for 2.9 into the equation, but I still think it's unreliable.)
What if you consider both tanks as a unit: the tank in your car and the non-metered fill tank, I assume in your garage. Start with a full tank in the garage, fill up the car, then measure how many gallons it takes to refill the tank in the garage. Or put a dipstick into the fill tank in the garage at start and again at finish. You'd have to figure a graduated metric on the stick. The utility of this method may depend on the size/type/shared use of the filler tank.
Or average mileage over several tanks if you can't refill the "filler" tank immediately after filling the car. As long as you can track the miles driven from one "fill" of the filler tank to the next fill, your mpg will be more/less accurate.
Trying to account for the amount of fuel that goes out of (or in to) the filler rather than relying on always being able to go from full-to-low-light in the car for that fixed quantity seems a more practical method. It also lets you refill at levels above the low light so you don't have to wait until you're on E to fill up.
*Note: VO used as a mileage enhancing additive to the trace amount of diesel that actually burns as fuel, just to be legal in most states...
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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.