| | Petrolia, TX | Hico, TX | United States |
| Population | 380 | 1,721 | 329,725,481 |
| Female Population | 50.5% | 56.2% | 50.5% |
| Male Population | 49.5% | 43.8% | 49.5% |
| Median Age | 55.6 | 33.9 | 38.4 |
| space3 | | | |
| Population - 2010 | 685 | 1,381 | 309,327,143 |
| Population - 2000 | 782 | 1,341 | 285,036,114 |
| Population - 1990 | 762 | 1,342 | 251,960,433 |
| Pop. 2000 to Now | -14.2% | 7.2% | 15.6% |
| Pop. 1990 to Now | -11.9% | 7.1% | 30.8% |
| space4 | | | |
| Population Density | 514.2 | 955.1 | 93.4 |
| Land Area | 0.7 | 1.8 | 3,531,905.4 |
| Water Area | 0.0 | 0.0 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Petrolia, TX | Hico, TX | United States |
| Age 0 to 4 | 6.3% | 12.1% | 5.9% |
| Age 5 to 9 | 0.0% | 12.5% | 6.1% |
| Age 10 to 14 | 7.4% | 3.4% | 6.6% |
| Age 15 to 17 | 0.0% | 3.3% | 3.9% |
| Age 18 to 20 | 1.6% | 2.8% | 4.0% |
| Age 21 to 24 | 4.5% | 2.0% | 5.2% |
| Age 25 to 34 | 1.8% | 14.3% | 13.8% |
| Age 35 to 44 | 9.2% | 8.2% | 12.9% |
| Age 45 to 54 | 17.6% | 5.5% | 12.6% |
| Age 55 to 59 | 7.1% | 6.0% | 6.7% |
| Age 60 to 64 | 7.1% | 7.7% | 6.3% |
| Age 65 to 74 | 13.9% | 6.6% | 9.6% |
| Age 75 to 84 | 18.4% | 5.7% | 4.5% |
| Age 85 and over | 5.0% | 10.0% | 1.9% |
| space1 | | | |
| Race | | | |
| | Petrolia, TX | Hico, TX | United States |
| White | 91.8% | 93.3% | 59.4% |
| Black | 0.0% | 0.3% | 12.2% |
| Asian | 0.0% | 0.5% | 5.6% |
| Native American | 0.0% | 0.1% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.0% | 0.0% | 0.4% |
| Two or More Races | 5.3% | 0.6% | 3.2% |
| Hispanic | 2.9% | 5.1% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Petrolia, TX | Hico, TX | United States |
| Married Population | 48.5% | 44.4% | 49.8% |
| Currently Married | 45.1% | 43.1% | 48.0% |
| Married but Separated | 3.4% | 1.2% | 1.8% |
| Single Population | 51.5% | 55.6% | 50.2% |
| Never Married | 12.2% | 22.1% | 33.8% |
| Divorced | 18.0% | 17.7% | 10.8% |
| Widowed | 21.3% | 15.9% | 5.6% |
| space5 | | | |
| Household Size | 1.93 | 2.86 | 2.60 |
| Households | 197 | 589 | 124,010,992 |
| Family Households | 117 | 275 | 80,755,759 |
| Married couple, w/children | 17.9% | 25.1% | 30.5% |
| Married couple, no children | 48.7% | 49.5% | 42.9% |
| Non Family Households | 80 | 314 | 43,255,233 |
| Single householder, w/children | 17.9% | 18.9% | 15.8% |
| Single householder, no children | 15.4% | 6.5% | 10.8% |