Book of Oil is an online video slot by Endorphina.
Return to Player (RTP): 96%
The slot has 10 paylines, while the maximum payout per spin can reach x5,000 of the bet.
Features and the main game mode
1. Winning combinations
High-value symbols pay from 2 of a kind, and low-value symbols pay from 3.
2. Wild symbol
Wild replaces any symbols and plays as a Scatter, triggering the bonus game.
Wild has its own value:
- 3 Wild symbols = x2 of the bet
- 4 Wild symbols = x20 of the bet
- 5 Wild symbols = x200 of the bet
On an active payline:
- 2 Wild symbols = x1 of the bet
- 3 Wild symbols = x10 of the bet
- 4 Wild symbols = x100 of the bet
- 5 Wild symbols = x500 of the bet
Bonus game mode
1. Trigger
The bonus game starts when 3, 4, or 5 Wild symbols appear on the reels.
2. Number of free spins
The number of free spins is set at 10.
The player has a chance to win extra free spins.
3. Expanding symbols
At the beginning of the bonus game, one of the symbols is selected to become an expanding one.
Payouts for such symbols are awarded regardless of whether they appear on consecutive reels or not.
4. Extra free spins
When 3 or more Wild symbols appear, the player wins 10 additional free spins.
Buy Bonus
If the player does not wish to wait, they can buy a bonus game at any point.
The following options are offered for purchase:
a. Buy for x76 of the bet.
Expanding symbol: 10.
b. Buy for x98 of the bet.
Expanding symbol: J.
c. Buy for x85 of the bet.
Expanding symbol: Q.
d. Buy for x120 of the bet.
Expanding symbol: K.
e. Buy for x86 from the bid.
Expanding symbol: A.
f. Buy for x69 of the bet.
Expanding symbol: Money.
g. Buy for x71 of the bet.
Expandable Symbol: Barrels.
h. Buy for x77 of the bet.
Expanding symbol: Oil well.
i. Buy for x133 of the bet.
Expanding symbol: Tycoon.
