Would You Suggest a Gas or Diesel Generator for Longevity?

Gasoline:

Advantages: Common fuel source - easily obtained Increases portability of smaller generators

Disadvantages: Highly flammable. Short shelf life of fuel, (approximately 12 months). Storing large quantities of fuel is hazardous. May not be available during power outages. Somewhat expensive fuel. Check your local prices, inefficient.

Diesel:

Advantages: Least flammable fuel source Fuel easily obtained (fuel is easier to obtain during a disaster because it is a necessary fuel for the military, trucking industry, and farming operations). On site fuel delivery available. Engine life for liquid-cooled 1800 RPM engines can approach 20,000 hours if properly serviced depending on the application and environment. High speed 3600 RPM diesel engines normally have a 10,000 to 15,000 hour life expectancy with proper maintenance and service under most conditions. Less expensive to operate. The general rule of thumb for fuel consumption is 7% of the rated generator output (Example: 20 kW x 7% = 1.4 gallon per hour at full load). Designed for off-road applications and can operate on dyed or farm/construction diesel fuel which is sold without the road tax and thus is considerably cheaper to purchase. Engines designed to work under a load for long periods of time and perform better when worked hard, rather than operated under light loads. Can operate in sub-arctic conditions with fuel additive. Equipment is competitively priced for a comparative sized water-cooled gaseous models with the same features. In high use situations overall long term cost of operation is much lower than gaseous Gen-Sets. 

Disadvantages: 18-24 month shelf life, without additives Installing large storage tanks raises cost of system. May not be available during power outages. Diesel fuel storage must be considered relative to required run time in your geographical area. If you live in hurricane country you might need a large fuel tank due to the high possibility of extended power outages. Engine noise is higher on a diesel compared to a gaseous engine. Use of a properly designed enclosure and sound attenuation system is more critical on a diesel engine system. Subject to "wet stacking" or over fueling if run for long periods of time with ultra light loads (less than 40% of the rated output). "Wet Stacking" causes the engine to smoke and run rough because the injectors become carbonized. Running a heavy load will usually clean up the over-fuel condition and allow the engine to perform normally. Diesel engines operate better and are more fuel efficient when loaded (70-80% is optimum). In sensitive emission areas in some states diesel engines are prohibited from operating over a prescribed number of hours per year to help reduce pollution levels. Requires clean moisture free fuel and a bit more maintenance than a comparable gaseous unit; Some cities and counties require the generator on-board fuel tanks to be double-wall containment type which can increase the cost of the generator system. Typically heavier and require more planning to load and unload than a lightweight gaseous Gen-Set.