• Warren Buffett's company has bet about $27 billion on Chevron and Occidental Petroleum this year.

• The Berkshire Hathaway CEO has discussed the oil business many times over the years.

• Here are eight of Buffett's most insightful quotes about investing in oil companies.

Warren Buffett's Berkshire Hathaway has waded deep into the oil business this year, plowing an estimated $27 billion into two fossil-fuel stocks.

The famed investor's conglomerate spent roughly $17 billion quadrupling its stake in Chevron to around 8% in the first quarter, and has paid nearly $10 billion to purchase over 19% of Occidental Petroleum since the end of February.

Buffett has previously shared his views on the oil industry, helping to put those enormous wagers in context. He has boiled down investing in an oil producer to betting on the price of oil over time, and downplayed his own track record in the space. He has also underlined the importance of discovery-and-development costs, and predicted oil would be usurped by a cleaner energy source within a century.

Here are 8 of Buffett's best quotes about oil, lightly edited for length and clarity:

1. "When you buy into a huge oil production company, how it works out is going to depend on the price of oil to a great extent. It's not going to be your geological home runs or super mistakes or anything like that. It is an investment that depends on the price of oil." (2020)

2. "You've stuck a lot of straws into the Earth, and it is a finite number. So, the one thing I can almost promise you is that oil will sell for a lot more someday." (Buffett was referring to the large number of oil rigs and wells worldwide, and the increasing scarcity of oil.) (2011)

3. "We have not distinguished ourselves, at all, in the oil-and-gas field, although we've made a little money. We will not be buying, very often, oil-and-gas stocks. But we probably haven't bought the last one." (Buffett was referring to Berkshire's ill-fated bets on ConocoPhillips and Exxon.) (2015)

4. "If we were in an oil stock, it's because we think it offers a lot of value at this price, but it does not mean that we think the price of oil is going up. If we thought oil was going up, we could buy oil futures, which we actually did once." (Berkshire purchased derivative contracts for about 46 million barrels of oil in the mid-1990s.) (2007)

5. "If oil goes from $30 to $60 a barrel, there's no reason in the world why oil executives should get paid more for what's going on. They didn't get it to $60 a barrel. If they have low finding costs, which is under their control, I would pay like crazy for that. A person who finds oil and develops reserves at $6 a barrel is worth a lot more than somebody that finds and develops them at $10 a barrel, assuming they're similar-quality reserves." (2007)