Methods to reduce frequency of diesel particulate filter regeneration

A method of reducing measured regeneration frequency of a diesel particulate filter in a vehicle combusting diesel fuel, the method comprising:

• (a) combusting a diesel fuel in a vehicle engine, wherein the vehicle includes a diesel particulate filter associated with the engine and wherein the diesel particulate filter requires regeneration thereof, the diesel fuel having less than about 50 ppm of sulfur and a diesel fuel additive including
• (i) a hydrocarbyl substituted dicarboxylic anhydride derivative prepared by reacting a hydrocarbyl-substituted succinic acylating agent with an amine, polyamine, or alkyl amine having one or more primary, secondary, or tertiary amino groups;
• (ii) a quaternary ammonium internal salt obtained from amines or polyamines that is substantially devoid of any free anion species comprising a compound of formula (VI):
• wherein
• R and R′ are independently alkylene linkers having 1 to 10 carbon atoms;
• R12 is a hydrocarbyl group or optionally substituted hydrocarbyl group, or an aryl group or optionally substituted aryl group;
• R13 is independently a linear or branched C1 to C4 alkyl group;
• and
• R14 is a hydrogen or a C1 to C4 alkyl group;
• and
• (iii) a thiazole, triazole, thiadiazole, a tolytriazole, or combinations thereof;
• (b) regenerating the diesel particulate filter while combusting the diesel fuel;
• and
• (c) comparing the frequency of regeneration of the diesel particulate filter when combusting the diesel fuel comprising the additives with the frequency of regeneration of the diesel particulate filter when combusting a diesel fuel which is devoid of the additives;
• wherein the frequency of regenerations per 1000 miles of the diesel particulate filter when combusting the diesel fuel comprising the additives is lower than a frequency of regenerations per 1000 miles of the diesel particulate filter when combusting a diesel fuel in the engine devoid of the additives.