I just purchased a Silverado 2500 HD. It's a gas engine. I want to put an Aux tank on it, but most of them say Diesel only. Is this just a CYA liability issue, or is there really a reason that you can't use the tank for gas?

Hello Carol ... Welcome to the forum ...
Gasoline has a high vapor pressure. The fumes are more explosive and polluting than diesel. So... an auxillary tank has to have a vapor recovery system. In the bad old days, the tank was merely vented. If you had a vented gasoline tank today, the gas would leak in a roll-over... bad for anybody around the wreck. And the vapors venting on a warm day would be dangerous and polluting as mentioned.

I have a 8.1 liter gasoline engine in my truck. It uses a lot of fuel towing my horsetrailer. If I'm going somewhere new for a trail ride, I'll carry a 5 gallon can of gas tied in the truck bed. That gas can will get me 50 miles to refuel if I needed to. (Like if the fuel gauge malfuntioned or I missed the last open gas station) I've never "Needed" it. I figure the risk of a wreck and the small gas can in the truck are low. It can be quickly removed in an emergency, unlike a large auxillary tank. The frequent fueling stops are good for me and the horses. That honk'in powerful engine will pass anything on the road except a fuel station.

One more issue... Diesel will get more miles per gallon than gasoline. In energy equivalents, a gallon of Diesel is the same as 1.112 gallons of gasoline. Or about 111 percent. But the diesel engine option costs about $4,000 more. Diesel engine maintenance also costs more. Currently the price of diesel in my area is $2.59 per gallon and Gas is $1.59 per gallon. Diesel would have to drop to $1.429 to break even with gasoline.

Gasoline is definitely the low cost fuel today