KE9NS

FYI about a barrel of crude oil:

40% gasoline (short hydrocarbon chains used in Otto cycle IC engines, does not allow for very high compression due to the short chains)

20% diesel (long hydrocarbon chains used in Diesel cycle IC engines, requires high compression due to long chains)

Longer chains like diesel fuel are further down the distillation chain and so contain higher sulfer levels than the shorter gasoline. This requires additional refining (beyond gasoline type refining) to remove the impurities (like sulfer).

Gasoline is based mostly on Octane chains (8 long). A purer octane fuel (like Premium) offers much higher stability (less unintentional detonation) and allows for higher compression engines, but costs more. The addition of Ethanol to gasoline raises the "octane rating" (ability to handle higher compression), but contains less energy by volume.

 

DIESEL CYCLE FUEL / ENGINES

Diesel engines are known for better fuel efficiency (20% better) than the lower compression Otto engines. This is due to longer chains in the fuel (more energy by volume) which allows for higher compression (which allows for more energy extraction).

However, high energy diesel fuel cannot operate at low temperatures and must be mixed with lower energy diesel fuel (which negates the benefits). Also, diesel fuel is inherently dirty and now requires extra refining to remove much of this dirt/sulfer and requires the engine to have filters.

Diesel fuel costs more than gasoline based strictly on the fact that there is more than twice the amount of gasoline than diesel fuel distilled per barrel of crude oil. Also, diesel now requires more refining to reduce sulfer levels, which in turn adds to its cost at the pump.

Newer low sulfer diesel engines now require special particulate systems that include spraying ammonia onto the exhaust.

Europe taxes Diesel less than gasoline to promote its use.

There is not nearly enough Diesel for everyone to change over.

Diesel cars can be adapted to use used cooking oil, which can be obtained for free while demand is low. However cooking oil has much less energy than petroleum based fuel (which negates all the mpg benefits) and requires additional filtering (refining) to be usable and so is not practical in the long term. Also, the supply of cooking oils, etc., is so small that it has no potential to reduce petroleum dependance (especially if we all stop eating fried foods).

OTTO CYCLE FUEL / ENGINES

Gasoline is more plentiful than diesel fuel and can be more easily refined from high sulfer crude.

Should be less expensive than Diesel however, currently states require reformulated gasoline that adds to the cost. Soon, Diesel will require additional refining to reduce sulfer, this will increase its cost. When the use of Diesel in passenger cars goes up, states will require additional refining to diesel fuel (just as with gasoline) as well and its benefits will dissappear.

Vehicles that run on gasoline can be adapted to use Ethanol fuels. We could eliminate our need for foreign oil if we all switched to E85 fuel. However, there is not enough domestic supply of Ethanol at this time, but there could be. Also, Ethanol fuels like E85 have much less energy than gasoline so its use only benefits our dependance on foreign oil, not mpg or price.

E85 engines can operate at much higher compression levels. This can translate into mpg levels equivalent to standard gasoline engines.

Production of Ethanol is inefficient and requires new techniques to make it worthy.

 

HYBRID IC / ELECTRIC ENGINES

Hybrids take advantage of energy wasted during driving. Braking energy is converted to electricity and stored in a battery pack. Engine Idle time is eliminated. Low RPM engine situations are eliminated. Energy stored in the batter pack is converted back into motion via an electric motor.

Improved efficiency over IC engine alone may not offset the complexity required to achive it. (i.e. Cars could be made of Carbon-Carbon instead of steel, to reduce weight and greatly improve mpg, but the cost and energy to manufacture it greatly outways the benefits)

No study done of the energy that goes into manufacturing the electric motor, additional controls, and limited life battery pack (and future disposel of) vs. the energy saved over the cars limited life span. I suspect its a losing proposition (even in high volume).