Immolate: which rank to use

Warlock · Fire · 8 ranks, 4 learned by level 30.

At level 30 with 45 spell power, Immolate rank 1 gets the most damage per mana; rank 4 does the most damage per second.

Most mana-efficient rank by gear: rank 2 up to 6, rank 1 from 7 spell power.

Every rank at level 30 with 45 spell power

Rank	Damage per cast	Mana	Cast	Damage per mana	DPS	Mana lasts
Rank 1 (level 1)	64 (64–64)	25	2 s	2.56	32	2 min
Rank 2 (level 10)	89 (89–89)	45	2 s	1.98	44.6	1 min 7 s
Rank 3 (level 20)	136 (136–136)	90	2 s	1.51	68.1	33 s
Rank 4 (level 30)	189 (189–189)	155	2 s	1.22	94.6	19 s

DPS counts the global cooldown. Mana lasts: casting only that rank from 1,500 mana.

Rank 1: 64 damage for 25 mana in Forever instead of 41 for 25 in Classic Era (spell power share 0.850 instead of 0.243).
Rank 2: 89 damage for 45 mana in Forever instead of 87 for 45 in Classic Era (spell power share 0.850 instead of 0.530).
Rank 3: 136 damage for 90 mana in Forever instead of 181 for 90 in Classic Era (spell power share 0.850 instead of 0.850).
Rank 4: 189 damage for 155 mana in Forever instead of 293 for 155 in Classic Era (spell power share 0.850 instead of 0.850).

From the client, for each rank: base damage or healing and its range (SpellEffect base points and variance), the extra per level up to the rank's max level, the spell power share (coefficient), mana cost, cast time, duration, global cooldown and cooldown.
No downrank penalty in the Forever client. Classic Era's client puts a penalty for spells learned before level 20 inside the coefficient (Shadow Bolt rank 1: 0.14); Forever's client gives the full share (0.486), for 80 low-level ranks across the classes. Anything else would be on Blizzard's servers, so the calculator shows Classic's rules only as Speculation.
Speculation: crits count only on direct hits, at 150%, as in Classic; the example gear (1.5 spell power per level) is not client data.