Are there laws in the United States against adding larger replacement or auxiliary fuel tanks to vehicles?

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Jim O questioned:

I handbook a jeep cherokee and want a better fuel tank. Yes, I know some of you would say I must handbook a smaller, more fuel efficent vehicle, but I like my jeep. I handbook alot between New York, New Jersey and down to North Carolina and some era additional than. I am exhausted of huge up each approx 400 miles (hwy). My jeep now has a 20.1 gallon fuel tank and I want to add a better substitution tank or an auxiliary tank. I have done a modest investigate and found some sold in Australia and France, but I cannot find anything in the US. Are here laws forbidding this? I have also looking into converting hybrid but can’t find anything value tiresome on my only vehicle. For now, until the prices of factory built hybrid (or better) SUVs become cheaper more usually avalible, I would just very get a better fuel tank and keep my jeep as fuel efficent as possible. So, are better substitution or auxiliary tanks allowed in the US, if so where can I find one?

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