Some analysts see a growing upward momentum for oil and note the latest data from the New York Mercantile Exchange points to an increase in investment by large funds.
"It is the first time this year that the large speculative funds are showing a net long position in crude oil," said Olivier Jakob, an analyst at Swiss-based Petromatrix.
Oil prices have swung between a high of $78.40 last July, when fighting flared in Lebanon, and a 20-month low of $49.90 in January when an expected influx of fund money failed to materialise, disappointing oil investors.
A steady recovery in prices since late January has been supported by gradually tightening supplies -- OPEC has twice cut output since November -- and by concerns over a possible disruption of Iran's oil supplies.
Strong net-long positions entering the market + decreased supply because of production cuts + summer driving season + Iranian tensions = higher prices.