Let me take a few minutes to summarize the results of the first quarter, then afterwards, we'll open up for questions about our results. As all of you have seen, diluted earnings per share for the first quarter were $1.01 compared to $1.03 for the same quarter a year ago. Results reflect strong gains inside our stores, especially in Prepared Foods. Excluding gasoline, gross profit increased over 13%. I will go over each category to give more details on what is driving these results.
Our fuel margin improved each month throughout the quarter as the wholesale cost of fuel declined, resulting in a fuel margin of $0.149 per gallon. Our average gasoline margin for the past 4 years has been $0.143 per gallon. Same-store customer traffic slowed significantly in the quarter due to excessively hot weather conditions throughout a major portion of our marketing territory. As a result, same-store gallons sold in the quarter were down 0.2%. However, total gallons sold for the quarter increased 3.7% to 394.1 million. The average retail price during this time was $3.38 per gallon compared to $3.63 in the same quarter last year.
Due to a lower gasoline margin compared to a record margin a year ago, gross profit in the quarter was down 10% to $58.8 million. Same-store gallons sold in August are trending positive.
Sales in the Grocery & Other Merchandise category were solid in the first quarter, despite being impacted by the previously mentioned weather and changes in the cigarette environment. Same-store sales rose 2.6% with total sales up 5.7% to $386.1 million. During the quarter, primarily in July, we experienced one of the hottest periods on record, pushing same-store customer count to the lowest level in over 3 years. We also incurred a change in the cigarette tax in one of our largest states, resulting in cigarette carton volume dropping significantly. Excluding cigarettes, same-store sales were up 6.4% during the quarter.