1. Decimals aren't hard.
2. I don't really need a calculator to do that.
3. The smaller the metric, the more accurate the reading is. You're in engineering mate; I don't need to tell you that. Especially for small values. Don't like decimals? They can then just round up or down.
Same with weight. Some people go by STONES. WHY? You don't buy food, meat and groceries by stones do you? You buy them in kilos. Hence, when you're measuring weight, measure in KILOS! Its easier to track smaller gains/losses that way. Ditto for fuel. Plus, kmpl is universal. The Americans don't have to convert our gallons and we don't have to convert theirs.
Buy in kilos. Measure in kilos.
Buy in litres. Measure in litres.
More accurate, by far, without the hassle of conversions and approximations. But... to each his own. I'll stick to kmpl.
Added you, SkyBaba...!