Abstract: The propagation of a temperature wave front in an enclosed space containing a gas features the measurement of the time which elapses between the passage of a temperature wave front past two thermionic probes 5, 6 mounted on the wall 4 of an enclosed space 3 arranged substantially along an axis 9 of propagation of the wave front and separated by a known distance.

Abstract: Additive formulation for engine fuels incorporating at least one constituent (A) and at least one constituent (B), constituent(A) consisting of at least one composition incorporating products resulting from the reaction of at least one dicarboxylic compound(D), whose carboxylic functions are separated by at the most eight carbon atoms, with at least one polyoxyalkylene glycol or glycol mono-ether (E) of general formula (I):R.sup.1 --O--(R.sup.2 --O).sub.n --H,in which R.sup.1 represents a hydrocarbon group having 1 to 30 carbon atoms, R.sup.2 represents a divalent hydrocarbon group having 2 to 6 carbon atoms and n is a number from 1 to 60; and constituent (B) consisting of at least one detergent-dispersant product. This formulation preferably also comprises a constituent (C) chosen from within the group formed by mineral or synthetic lubricating oils and polyglycols soluble in the fuel.

Abstract: An additive composition for fuels comprising at least one constituent (A) and at least one constituent (B), the said constituent (A) comprising at least one multinitrogen-containing compound of general formula (I): ##STR1## where R.sup.1 and R.sup.2, which are the same or different each represent a hydrocarbon group or a group of formula R.sup.5 --(--O--R.sup.6 --).sub.a --(--O--R.sup.7 --).sub.b --, R.sup.3 is a hydrocarbon group or a group of formula R.sup.8 --(--X--R.sup.9 --).sub.c --(--X--R.sup.1 O--).sub.d --(--X--R.sup.1 1--).sub.e -- in which X is selected from the groups --O-- and --NR.sup.1 2--, R.sup.5, R.sup.6, R.sup.7, R.sup.8, R.sup.9, R.sup.1 0 and R.sup.1 1 each represent a hydrocarbon group, a, d and e are each zero or a whole number, b and c are each a whole number, R.sup.4 and R.sup.1 2 each represent a hydrogen atom or a hydrocarbon group and n is a number from 0 to 20 and the said constituent (B) comprises at least one polyglycol which is soluble in the fuel in question.