| Oil-rich Canadian province | 26 |
| Oil-rich African country | 24 |
| Oil-producers' org. | 23 |
| Oil-producers' gp. | 22 |
| Oil-fire extinguisher Red ___ | 29 |
| Oil-drilling structure | 22 |
| Oil-drilling equipment | 22 |
| Oil-drilling apparatus | 22 |
| Oil-catching receptacle | 23 |
| Oil-burning iron lantern | 24 |
| Oil, in mechanic-speak | 22 |
| Oil well, for instance | 22 |
| Oil well firefighter Red ___ | 28 |
| Oil well firefighter Red | 24 |
| Oil well firefighter of note | 28 |
| Oil well fire fighter of note | 29 |
| Oil well drilling gear | 22 |
| Oil used in church rites | 24 |
| Oil tycoon Halliburton | 22 |
| Oil spill-monitoring org. | 25 |
| Oil sources for oil paint | 25 |
| Oil producer's grp. | 23 |
| Oil price-setting grp. | 22 |
| Oil Patch installation | 22 |
| Oil partner in soapmaking | 25 |
| Oil painter's mixture | 25 |
| Oil or vinegar container | 24 |
| Oil on a wall, for example | 26 |
| Oil of ___ (cosmetics brand) | 28 |
| Oil of wintergreen, e.g. | 24 |
| Oil of wintergreen source | 25 |
| Oil of wintergreen is one | 25 |
| Oil of rose petals, e.g. | 24 |
| Oil obtained from flowers | 25 |
| Oil name from long ago | 22 |
| Oil ministers' org. | 23 |
| Oil ministers' grp. | 23 |
| Oil magnate J. Paul ___ | 23 |
| Oil low in erucic acid | 22 |
| Oil giant with HQ in Vienna | 27 |
| Oil giant based in Memphis | 26 |
| Oil giant acquired by BP | 24 |
| Oil from orange flowers | 23 |
| Oil from orange blossoms | 24 |
| Oil from flower petals | 22 |
| Oil for the lamps of Roma | 25 |
| Oil fire fighter Red ___ | 24 |
| Oil filter accumulation | 23 |
| Oil field investigation | 23 |
| Oil drilling equipment | 22 |
| Oil driller's setup | 23 |
| Oil directly from a well | 24 |
| Oil company mercenary? | 22 |
| Oil company in a 1999 merger | 28 |
| Oil company acquired by BP | 26 |
| Oil city on the Caspian | 23 |
| Oil city of west Texas | 22 |
| Oil cartel's letters | 24 |
| Oil cartel's inits. | 23 |
| Oil cartel's initials | 25 |
| Oil cartel based in Vienna | 26 |
| Oil and vinegar, maybe | 22 |
| Oil and vinegar holders | 23 |
| Oil and vinegar holder | 22 |
| Oil and vinegar concoction | 26 |
| Oil and vinegar alternative | 27 |
| Oil and gasoline giant | 22 |
| Oil additive since 1954 | 23 |
| Oil a portion of veal? | 22 |
| Ohne, across the Rhine | 22 |
| Ohio/Ontario separator | 22 |
| Ohio-Ontario separator | 22 |
| Ohio-born humorist Bombeck | 26 |
| Ohio-based faucet maker | 23 |
| Ohio's state insect | 23 |
| Ohio's state flower | 23 |
| Ohio's rubber city | 22 |
| Ohio's Lake ___ College | 27 |
| Ohio University mascot | 22 |
| Ohio travel-guide listings | 26 |
| Ohio town or its college | 24 |
| Ohio town near Steubenville | 27 |
| Ohio team, on scoreboards | 25 |
| Ohio State's conference | 27 |
| Ohio rubber plant site | 22 |
| Ohio political dynasty | 22 |
| Ohio or Utah, to René | 24 |
| Ohio or Colorado: Abbr. | 23 |
| Ohio or Arkansas, e.g. | 22 |
| Ohio Northern's town | 24 |
| Ohio Northern University town | 29 |
| Ohio NBAers, in headlines | 25 |
| Ohio liberal arts college | 25 |
| Ohio Indians, in the past | 25 |
| Ohio hoopsters, in headlines | 28 |
| Ohio hoopster, for short | 24 |
| Ohio hometown of LeBron James | 29 |
| Ohio home of the Wrights | 24 |
| Ohio governor Strickland | 24 |
| Ohio et al., to W. Va. | 22 |