I try to fill up before it gets into the red.
I figure the engineers are trying to tell us something with that red paint.

I'm told the in-tank pump is cooled by the fuel it's sitting in. Dunno if that's true. Pump intake hose also - is maybe more likely to dry out and rot if not soaking in fuel. And if it is compromised (perforated) sucking up fuel will be like sucking soda through a straw with holes in it.

Anyway, there's not that much real benefit in nearly draining the tank just to get an mpg value. You can calculate on combined numbers from two or three consecutive fillups and that should be pretty good.

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Apparently Volvo isn't that good at listing fluid capacity figures anyway. We ran a thread for about a week once, discussing how many quarts of oil are really needed when doing an oil change. I almost couldn't believe it, but Iwas guilty of participating. The book says four qt., but most of us seem to need about 4.3 qt. to get the oil to the top of the hash marks. Go figure. I figure that Volvo's 4 qts gets you to the middle of the marked range on the stick - maybe that's their target.

Then there's the five-speed standard tranny fluid amount. There's some word out there that says to tip the car and overfill by some amount, keeps the 5th gear better lubricated. I don't know, never drove one.
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Sven: '89 245, IPD sways, electric rad. fan conversion, e-codes, 28+ mpg - auto tranny. 850 mi/week commute. '89 245 #2 (wifemobile). '90 244 (spare, runs).