Millenium, as mentioned before, there is no reserve tank/light. You have a 71 litre tank and that is it. The light is a low fuel warning light. On mine, the low fuel warning light comes on with 70kms to go, how do I know that, well, the DTE on my trip computer indicates 80kms to go and as its interval is 10kms, the next change causes the low fuel light to come on. For accurate fuel usage without trip computers, run roughly the same distance and always fill up to the first click. Do this several times to get your average.