Additives for minimizing intake valve deposits, and their use

A fuel additive composition which comprises:

• a) a fuel-soluble Mannich detergent/dispersant formed from (i) one mole part of at least one hydroxyaromatic compound having on the ring an aliphatic hydrocarbyl substituent derived from a polyolefin having a number average molecular weight in the range of about 500 to about 3000, (ii) from 0.8 to 1.5 mole part(s) of at least one aliphatic polyamine having one and only one primary or secondary amino group in the molecule, and (iii) from 0.8 to 1.3 mole pan(s) of at least one aldehyde, with the proviso that the mole ratio of aldehyde to amine is 1.2 or less;
• and
• b) at least one liquid carrier for said Mannich detergent/dispersant in proportions such that for each part by weight of Mannich detergent/dispersant on an active ingredient basis there is in the range of about 0.3 to about 2.0 parts by weight of liquid carrier therefor.

A Mannich product composition formed from (A) one mole part of at least one hydroxyaromatic compound having on the ring an aliphatic hydrocarbyl substituent derived from a polyolefin having a number average molecular weight in the range of about 500 to about 3000, (B) from 0.8 to 1.3 mole part(s) of at least one aldehyde, and (C) from 0.8 to 1.5 mole pan(s) of at least one aliphatic polyamine with the provisos that:

• (1) the mole ratio of aldehyde to amine is 1.2 or less;
• and
• (2) the polyamine used in forming said composition has in the molecule one primary or secondary amino group capable of undergoing a Mannich condensation reaction with (A) and (B), the other amino group or groups in the molecule being substantially inert toward direct participation in such Mannich condensation reaction.