As I consider the difference between a diesel engine and a gas engine, I came across the following information.

Gas versus Diesel Engines

In a modern gasoline engine gas, or fuel, is delivered to each cylinder of the engine by a fuel injector. The injector sprays a fine mist of fuel into each cylinder just above the intake valve. This mixes with air that comes in through the air filter and related air intakes, then flows through the intake valve of each cylinder.
In a diesel engine, the fuel is injected directly into the cylinder. mixing with the air there.The diesel injector is within the combustion area of the engine, so diesel fuel needs to be “tougher” than gasoline.

Fuel Economy and Diesel Engines

Diesel engines get better fuel economy simply because they do not need to burn as much fuel as a gas engine to get the same power. Diesel engines are also built heavier than a gas engine to sustain the added stress of the higher compression ratio. Diesel engines do not have an ignition system so you will never have to give them tune ups.
Exhaust systems last longer because diesel fuel exhaust is not as corrosive a gasoline engine exhaust.
  • PRO: Diesels get great mileage. They typically deliver 25 to 30 percent better fuel economy than similarly performing gasoline engines.
  • CON: Although diesel fuel used to be cheaper than gasoline, it now often costs the same amount or more. Diesel fuel is also used for commercial trucks, home and industrial generators, and heating oil, so as demand for diesel passenger vehicles grows, the price of diesel fuel is likely to continue to rise because of competition from those other users.

Engine Performance

  • PRO: Diesel fuel is one of the most efficient and energy dense fuels available today. Because it contains more usable energy than gasoline, it delivers better fuel economy.
  • CON: Although diesel fuel is considered more efficient because it converts heat into energy rather than sending the heat out the tailpipe as gas-powered vehicles do, it doesn’t result in flashy high-speed performance. In some ways, a gasoline-powered engine is like a racehorse — high-strung, fiery, and fast — whereas a diesel engine is more like a workhorse — slower, stronger, and more enduring.

Diesel Engines and Noise

One big downside of diesel engines is that they are very noisy. You will get the typical diesel clatter at idle, but that goes away off idle. At normal driving speeds they are as quiet as a gasoline engine.
You won’t get the same acceleration that you get from a gasoline engine, but a turbo diesel will get up and go fairly quickly. You will need to adjust your driving habits somewhat also.

Maintenance of Diesel Engines

With gas engines but especially with diesel engines, regular oil changes are a must. Diesel fuel is not as refined as gasoline and the oil will get dirtier than a gasoline engine. Replace air and fuel filters once a year. If you live in a cold climate, you will need to switch to a winter blend fuel to prevent fuel gelling. There are additives you can put in the fuel to help prevent this as well.
  • PRO: Diesels have no spark plugs or distributors. Therefore, they never need ignition tune-ups.
  • CON: Diesels still need regular maintenance to keep them running. You have to change the oil and the air, oil, and fuel filters. Cleaner diesel fuels no longer require you to bleed excess water out of the system, but many vehicles still have water separators that need to be emptied manually.
  • PRO: Diesel engines are built more ruggedly to withstand the rigors of higher compression. Consequently, they usually go much longer than gas-powered vehicles before they require major repairs. Mercedes-Benz holds the longevity record with several vehicles clocking more than 900,000 miles on their original engines! You may not want to hang onto the same vehicle for 900,000 miles, but longevity and dependability like that can sure help with trade-in and resale values.
  • CON: If you neglect the maintenance and the fuel injection system breaks down, you may have to pay a diesel mechanic more money to get things unsnaggled than you would to repair a gasoline system because diesel engines are more technologically advanced.
  • PRO: Because of the way it burns fuel, a diesel engine provides far more torque to the driveshaft than does a gasoline engine. As a result, most modern diesel passenger cars are much faster from a standing start than their gas-powered counterparts. What’s more, diesel-powered trucks, SUVs, and cars also can out-tow gas-powered vehicles while still delivering that improved fuel economy.

Keeping Diesel Engines Warm

Replace glow plugs (the heating devices used to warm diesel engines so they start) every two years as well. If temperatures drop below 10 degrees Fahrenheit, it’s probably not a bad idea to use a block heater. This will ensure that your diesel engine starts easily in cold weather, especially with the heavier grade oil that diesel engines require. Just be sure you know what you’re doing; ask a mechanic for assistance if you want to install a block heater.
Information from articles by
 Matthew Wright and Deanna Sclar