Higher spell slots used for lower level spells?

[kolikeos]

A sorcerer has used up all his 3rd level spells. Can he use a 4th level slot to cast one of his 3rd level spells?

A wizard is obssesed with fireballs . Can he spend his 4th level spell slot to prepare another fireball?

Thanks in advance.

 

[Delta]

Yes. From the SRD:

Spell Slots
The various character class tables show how many spells of each level a character can cast per day. These openings for daily spells are called spell slots. A spellcaster always has the option to fill a higher-level spell slot with a lower-level spell. A spellcaster who lacks a high enough ability score to cast spells that would otherwise be his or her due still gets the slots but must fill them with spells of lower level.

 

[kreynolds]

You know, I've always been of the opinion that doing this should "heighten" the lower level spell up the level of the slot it is being placed in (where applicable). Bah.

 

[Beckett]

You know, I've always been of the opinion that doing this should "heighten" the lower level spell up the level of the slot it is being placed in (where applicable). Bah.

I was fond of Monte Cook's way in Arcana Unearthed, where a caster could weave together 3 lower slots to power a higher level spell, or use a higher slot to pay for two lower spells. I've tried porting it into regular D&D, but it requires some messing with memorization to work right.