Sources believed the adjustment was prompted by the prevailing tight supply and demand balance and rising crude oil prices over the previous couple of weeks.

Spot availability for most base oil grades was very limited, prompting increases for spot transactions as well.

Driven by similar market conditions, Chevron had lifted its Group II 100R and 220R oils by 10 cents/gal on July 26.

No additional price adjustments surfaced in the market this week.

Availability of base oils in the U.S. was not expected to improve until late August or September, when demand was likely to decline ahead of the fall/winter season, according to sources.

Meanwhile, market participants were also keeping a close watch on crude oil futures, as values had gradually crept up during the previous couple of weeks on expectations that Saudi Arabia and Nigeria would be trimming crude output.

However, oil futures retreated on Tuesday, with West Texas Intermediate falling back below $50 per barrel on signs of increased production by OPEC members.

West Texas Intermediate futures on the CME/Nymex traded at $49.16 per barrel on August 1, up $1.27/bbl from $47.89 per barrel on July 25.

Light Louisiana Sweet wholesale spot prices closed at $52.46 per barrel on July 31, compared with $48.78 per barrel on July 24, according to data from the U.S. Energy Information Administration.

Brent was trading at $52.63/bbl on the CME on Aug. 1, up $2.43/bbl from $50.20/bbl on July 25.

Low sulfur vacuum gas oil was at Sep WTI plus $8.25/bbl ($58.42/bbl), and high sulfur VGO was at crude plus $7/bbl ($57.17/bbl). In comparison, low sulfur VGO was trading at $54.99/bbl and high sulfur VGO was at $53.74/bbl on July 24, according to PetroChemWires Daily Refinery Focus.

Historic U.S. posted base oil prices and WTI and Brent crude spot prices are available for purchase in Excel format.