It was the final road game for the Brewers, who stayed 1 1/2 games behind Philadelphia for the third and final NL wild-card spot.
Milwaukee finishes with nine games at home against St. Louis, Miami and Arizona. The Brewers would lose any tiebreakers with the Phillies or San Diego because they lost the season series against both of them.
''We have given ourselves a chance on this homestand,'' Brewers manager Craig Counsell said. ''We have to win a lot of games, but we're capable of it. The fact that we're home is a good thing.''
Hunter Renfroe homered for the Brewers, who were unable to complete their first four-game sweep of the Reds since 2003. Renfroe who tied a career high with four hits including two homers and a season-high five RBIs on Saturday, homered on the first pitch leading off the second for a 1-0 lead.
Freddy Peralta, who hadn't pitched since Sept. 8 due to right shoulder inflammation, threw two innings before giving way to Aaron Ashby.
''One-time through the lineup is what we were thinking there (with Peralta),'' said Brewers manager Craig Counsell. ''The bullpen pitched well. The home run bit us.''
Cincinnati tied the score 1-1 in the fourth when Ashby hit Austin Romine with the bases loaded - one of two hit batters for Ashby.
Milwaukee's lone run and all of its hits against Lodolo came in the second inning.
''It was the third time I faced them this year,'' Lodolo said. ''Early on they were really on my heater. It wasn't locating it great. I threw in the change up. I've been working on it. The first two times I hardly threw any change ups. The swings I started getting on it today showed they were not geared up for it.''
Steer's solo home run leading off the eighth was his second homer, his first since his major league debut on Sept. 2.
''Those moments don't come around very often no matter who you are,'' Reds manager David Bell said. ''Spencer is going to be in that situation and is going to come through again, to directly win a game.''
Matt Bush (2-3) took the loss. Buck Farmer (2-1) got the win and Alexis Diaz earned his ninth save.
The Brewers were denied what could have been a two-run single by Tyrone Taylor and potentially a big second inning when the struck Keston Hiura between second and third for the final out. ''I think it was going to be by (Reds shortstop Kyle) Farmer and it clipped Keston,'' Counsell said. ''He's trying to get a jump off second. It was just unfortunate.''
Peralta was encouraged by his velocity in his two innings, but mostly that he didn't have any discomfort in his shoulder. ''Between innings I was feeling really good,'' he said. ''Before that was a problem. I can do more (next time out) I want to be part of this moment right now. It's time for us to keep winning games.''
Brewers: RHP Luis Perdomo was placed on the 15-day injured list, retroactive to Saturday, with a right calf strain.
Reds: OF Jake Fraley and INF Donovan Solano are dealing with an eye infection. It is uncertain whether they will travel to Pittsburgh where the Reds begin a series on Monday.
Brewers: RHP Adrian Houser (6-9, 4.62) starts Tuesday in the opener of a two-game series against the Cardinals.
Reds: RHP Chase Anderson (2-3, 5.21) will start the opener of a three-game series at Pittsburgh on Monday.
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