LOS ANGELES (CBSLA.com) — Gas prices in California are predicted to climb due to a switch to summer blend, according to consumer advocates.

Consumer Watchdog says prices will spike 30 cents by Friday, explaining that the Los Angeles wholesale market jumped 52 cents per gallon because of the switch.

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“It’s definitely not obviously what we want. It’s interesting how they kind of go influx in the winter months and they’ll go lower and so it’s just kinda being able to predict what’s gonna go up and come down,” said John Riding, a driver.

The Santa Monica-based group warned that drivers should fill up Thursday since prices are expected to go up by Friday and will keep climbing.

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“I’m sure a lot of people don’t know about that. I’m sure they’re gonna get gas sometime later this week and like, ‘Whoa, gas prices went up.’ ” said Kenneth Stevenson, another driver.

He was glad he had been warned of the anticipated spike in prices.

Consumer Watchdog also said oil refiners were profiting from the blend switch despite low crude oil prices.

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To find the cheapest local gas prices, visit cbsLA.com/gas.