Talk:Fuel consumption

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Thanks for this contribution --Eewadmin 04:56, 16 April 2008 (EDT)

Question

Petrol/gasoline varies in composition according to the season and, probably, even from batch-to-batch. Also, individual suppliers use different additives. What influence does this have on the consumption?

Secondarily, the addition of ethanol to fuel (now mandatory in the UK) increases the consumption. Should this be reflected in manufacturers' consumption figures? (I bet they aren't!!!) --Eewadmin 05:04, 16 April 2008 (EDT)

IME, the difference between summer and winter blends of gasoline is somewhere around 2-5%. It's hard to figure since warmer weather in general tends to increase mileage a few percent. Surprisingly enough, all the estimates of how much a vehicle would get on different blends, like E85 compared to gasoline from fueleconomy.gov, only use the difference in energy content and don't actually measure the change in efficiency as well. Naturally, since Ethanol blends have much higher octane, engine efficiency is noticeably better due to higher EGR rates/advanced timing but as for how much better it varies from vehicle to vehicle. I started a thread here discussing that but couldn't find anything concrete.--Roflwaffle 03:55, 28 April 2008 (EDT)

Thanks for this info and link. Interesting. One thing in the linked thread that I disagree with is the question of altitude improving consumption. I'm consistently finding that I get better consumption on my HCH when the barometric pressure is high. I impute this observation to a hypothesis that more oxygen is being pulled into the cylinder, so combustion of the heavier fractions is more complete. I don't suppose that the injection volumes are calculated with barometric pressure as a variable. The improvement is about 0.1 to 0.15 l/100 km per 10 hPa, between 1000 and 1030 hPa. --Eewadmin 07:46, 28 April 2008 (EDT)