fig1 shows a prior art system of subjecting fuel to a magnet field as it flows to a carburetor 20 of an internal combustion engine . the fuel flows through a metal fuel line 22 which terminates in a brass fitting 24 . a magnet 30 , such as produced by h . k . research and development , 33491 calle miramar , san juan capsitrano , calif ., and designated a hk - 12 unit is shown strapped to the fuel line 22 by nylon straps 32 and 34 . the hk - 12 magnet 30 is approximately 1 &# 34 ; high and 31 / 2 &# 34 ; square and produces approximately 940 gauss . this particular arrangement has been shown in increase the fuel mileage of diesel semi - trucks or tractors by approximately 12 . 8 percent as shown in table 1 . table 1 shows a test on a series of diesel tractors without the hk - 12 magnet assembly and with the hk - 12 magnet assembly . table 1______________________________________tractor without unit with only hk - 12 % increasenumber mpg mpg in mpg______________________________________ 70 4 . 56 5 . 40 18 . 42 72 5 . 60 6 . 12 9 . 29 74 5 . 36 6 . 29 17 . 35 75 5 . 25 5 . 55 5 . 71 76 5 . 47 5 . 75 5 . 12 77 5 . 30 5 . 83 12 . 71 83 5 . 06 6 . 40 26 . 48 84 5 . 00 6 . 30 26 . 00 88 6 . 07 6 . 19 1 . 28 89 4 . 98 5 . 09 4 . 20 94 5 . 91 6 . 32 7 . 37 96 5 . 91 6 . 24 7 . 28103 5 . 80 6 . 61 14 . 07104 5 . 38 6 . 59 22 . 50111 5 . 82 6 . 08 4 . 51112 5 . 48 5 . 78 6 . 06114 5 . 80 5 . 89 2 . 05115 5 . 47 6 . 40 17 . 00118 5 . 60 6 . 31 12 . 70121 5 . 77 5 . 88 5 . 26122 5 . 81 6 . 34 9 . 12131 5 . 43 6 . 25 15 . 10132 5 . 95 6 . 62 11 . 26134 5 . 72 6 . 28 9 . 80135 5 . 08 6 . 04 18 . 91136 5 . 48 5 . 79 5 . 71137 5 . 83 6 . 03 3 . 43138 4 . 84 5 . 37 10 . 95139 5 . 44 5 . 46 0 . 37140 5 . 12 5 . 44 6 . 25141 5 . 42 6 . 22 12 . 68143 4 . 83 5 . 27 9 . 11144 4 . 83 5 . 58 15 . 53145 4 . 84 5 . 43 12 . 20147 5 . 36 5 . 54 3 . 46148 4 . 92 5 . 40 10 . 06149 5 . 41 6 . 52 25 . 14150 5 . 74 6 . 83 15 . 51151 5 . 25 6 . 94 32 . 19162 5 . 23 6 . 14 18 . 41173 4 . 99 5 . 28 5 . 81174 5 . 63 5 . 84 3 . 73179 5 . 76 6 . 09 5 . 73185 5 . 31 5 . 78 8 . 90188 5 . 00 5 . 50 10 . 00189 5 . 33 5 . 97 12 . 00191 4 . 08 5 . 59 37 . 00192 4 . 95 6 . 44 30 . 10195 4 . 73 6 . 21 31 . 30196 4 . 87 6 . 22 27 . 72197 5 . 35 5 . 62 5 . 05198 4 . 82 5 . 98 24 . 07200 5 . 57 6 . 44 15 . 62201 4 . 71 5 . 66 20 . 17503 5 . 04 6 . 36 26 . 19average 5 . 31 6 . 00 12 . 82 % ______________________________________ the prior art magneto - hydrodynamic magnet unit 30 promotes improved burning of all hydrocarbon base fuels including gasoline , diesel , and propane . the magnet unit 30 is strapped to the fuel line 22 as close as possible to the carburetor 20 or fuel injection system . as fuel flows through the fuel line , it is influenced by a high intensity focused magnetic field which ionizes the fuel . this ionization process causes fuel hydrocarbons to exhibit a net positive molecular charge resulting in a hydrocarbon molecule that more readily bonds to the negative charged oxygen molecule . magnetically influenced fuel dissolves carbon build up in carburetor jets , fuel injectors , and combustion chambers thereby helping to clean the engine . the resultant conditioned fuel burns more completely producing a higher btu output , better fuel economy , more power , and reduced emissions . in the past , it was felt that a higher magnetic field would increase this effect on the fuel . however , almost all fuel lines used today are either metal , plastic or steel reinforced . when the magnet was placed on these fuel lines , the magnetic force dissipated both up and down the fuel line from where the unit is placed . within a few days the entire fuel line is magnetized but in a very weakened state . it was also found that some engines use brass fuel connectors on the fuel line . brass , it has been found , totally negates the magnetic force . also , metal surrounding the fuel line , such as the engine and other components , also attract the magnetic force from the unit and further dissipates the force . it has been found that by various improvements , the fuel mileage can be significantly increased by magneto - hydrodynamic effects . significant increase in fuel economy has been realized by the improvements shown in fig2 through fig4 . the first improvement is a fabric reinforced rubber fuel line assembly 40 having a rubber hose 42 such as a parker 296 - 101 / 2 &# 34 ; id rubber fuel line hose for delivering fuel from an inlet end to an outlet end . this fuel line assembly 40 has an outlet fitting 44 made of steel or aluminum . similarly , an aluminum or steel inlet fitting 46 is fitted to the inlet side of the fuel line assembly 40 . a banjo nut 48 made of steel or aluminum is used to attach the fuel line 40 the carburetor 20 . the key is that the fittings 44 , 46 , and 40 have no copper in these fitting such as is true with brass or copper fittings . the fuel line hose 42 is attached to the fittings 44 and 46 with non - metallic clamps 52 . a magnet assembly 41 , in this case , designated a 5hd magnet , is strapped by means of nylon straps 32 and 34 to the rubber fuel line 42 . the 5hd magnet 41 is approximately 51 / 2 &# 34 ; long , 11 / 2 &# 34 ; wide , and 2 &# 34 ; high and produces approximately 560 gauss . it has been found by experimentation that the field strength of magnet 41 should be between 500 gauss and 1 , 000 gauss . the increased length of this magnet induces the magnetic field over a longer portion of the fuel line 42 , thus , increasing the length of time that the magnetic field is induced in the traveling fuel . the larger diameter of hose 42 compared to the size of conventional metal fuel lines also slows the travel of the fuel increasing the time that the magnetic field is exposed to the fuel . a sheet rubber wrap 50 being approximately 111 / 2 &# 34 ; square by 1 / 8 &# 34 ; thick is wrapped about the magnet 41 and a portion of the fuel line 42 in contact with the magnet . this shield or rubber wrap 50 is held in place by two nylon straps 53 and 54 . it has been found that the rubber shield 50 , when used with gasoline engines , can be reduced in thickness to approximately 1 / 16 &# 34 ; while still maintaining its effectiveness . with these improvements , six diesel tractors were tested , similar to the method used in table 1 , with an increase in fuel mileage of 45 percent . this increase in fuel mileage is attributable to the fuel line being rubber , having a large id 60 as shown in fig4 and non - metallic reinforcement such as fabric fiber 62 . table 2______________________________________ with 5hd unittractor without unit and rubber wrap % increasenumber mpg mpg in mpg______________________________________ 71 3 . 52 4 . 92 40 . 07 82 5 . 00 7 . 28 45 . 60142 3 . 79 5 . 49 44 . 85180 4 . 06 6 . 22 53 . 20184 4 . 22 6 . 37 50 . 95187 4 . 50 6 . 10 37 . 11average 4 . 18 6 . 06 45 . 06 % ______________________________________ in an alternate embodiment of the invention shown in fig3 the rubber wrap 55 may be a two - piece molded unit whose seam overlap and are held together with non - metallic clamps 56 and 57 . this embodiment speeds installation time and reduces the package size of the unit , but at additional cost . referring to fig5 - 8 , an alternate form of a fuel conditioning apparatus or fuel conditioner 100 constructed in accordance with the present invention conditions and improves the utilization , emissions , and economy of fuel flowing through a fuel conveying or delivery means , such as a longitudinal portion of a fuel line 102 . as shown in fig9 the fuel flows in the direction indicated by arrows , such as arrow 104 , from a fuel source 106 toward a fuel distribution system 108 . the fuel source 106 may be a fuel pump filter , and the fuel distribution system 108 may be a carburetor for gasoline - powered engines , or a fuel injector into a cylinder for a diesel - powered engine . the fuel line 102 , and the manner of coupling the fuel line to the fuel source 106 and fuel distribution system 108 , may be as described above for the embodiment of fig2 - 4 . the fuel conditioner 100 may include two fuel conditioner assemblies , an upstream assembly 110 and a downstream assembly 112 , relative to the direction of fuel flow shown by arrow 104 . each fuel conditioner assembly 110 , 112 includes a magnet assembly 114 having at least one magnet 116 lying adjacent an exterior surface of the fuel line 102 . in the illustrated embodiment , the magnet assembly 114 has a second magnet 118 which is oriented with respect to magnet 116 for a magnetic attraction therebetween . for example , referring to fig7 and 8 , the magnet 116 has a north pole or north magnetic face 120 lying adjacent the exterior surface of fuel line 102 . the magnet 116 has an opposing south pole or south magnetic face 122 which is in contact with a north pole or north magnetic face 124 of magnet 118 . the magnet 118 also has a south pole or south magnetic face 126 facing away from the fuel line 102 . as shown in fig5 and 6 , the magnets of the fuel conditioner assembly 112 have a different orientation than the magnets of assembly 110 . this different orientation is indicated by designating the magnets of assembly 112 as magnets 116 &# 39 ; and 118 &# 39 ;. the magnet 116 &# 39 ; has the south magnetic face 122 lying adjacent the fuel line 102 , while magnet 118 &# 39 ; has the north magnetic face 124 facing away from the fuel line 102 . the north magnetic face 120 of magnet 116 &# 39 ; is aligned with the south magnetic face 126 of magnet 118 &# 39 ;. the magnets 116 and 118 are preferably porcelain or ceramic magnets , each having a 2 , 000 gauss magnetic charge . such magnets may be obtained from magnetic specialties of wood village , oreg . 97060 , as part no . mcz - c - 35 . it is preferred to use the magnets 116 and 118 without any coating or covering surrounding the magnet faces 120 - 126 . magnets with a plastic coating have proved to be inferior during use . due to the heat within the engine compartment , such plastic coatings may melt when installed on some engines . plastic coatings are also believed to decrease the flux produced by the magnets to one half of the rated gauss value . thus , bare ceramic magnets 116 and 118 are preferred . the fuel conditioning assemblies 110 and 112 each include shielding means , such as a rubber shield 130 for substantially surrounding and shielding the magnet assembly 114 and the fuel line 102 . the rubber shield 130 also serves to shield a magnetic field induced by the magnet assembly 14 into fuel flowing through the fuel line 102 in the same manner as described above with respect to the embodiment of fig2 - 4 . as best shown in fig7 the rubber shield 130 may be a molded 1 / 8 inch thick rubber body including a magnet receiving portion 132 defining a magnet receiving cavity 134 therein . the cavity 134 includes an outer region 136 for receiving magnet 116 , and an inner region 138 for receiving magnet 118 . the rubber shield 130 also includes a skirt portion 140 having legs 142 and 144 for extending around and surrounding the fuel line 102 . the skirt portion 140 also has a longitudinally extending portion 146 for extending along a portion of the exterior surface of fuel line 102 . the rubber shield 130 includes a flush face portion 148 which advantageously allows the shields 130 of the conditioner assemblies 110 and 112 to be positioned side - by - side in contact with one another , as shown in fig5 and 6 . for some applications , it may be desirable to longitudinally separate the two fuel conditioning assemblies 110 and 112 from one another by a distance of less than one inch . in some applications , a separation distance ( not shown ) of 3 / 4 inch may provide optimal fuel economy . however , for the majority of applications , an abutting relationship between the two fuel conditioner assemblies 110 and 112 is believed to provide the best performance . the fuel conditioner 100 also includes magnetic field focusing means , such as a focusing bar 150 of a ferrous steel , such as commercial grade , cold rolled 12 - gauge steel , for instance , having a size of 1 / 4 inch by 21 / 2 inches . for example , the focusing bar may be of a low carbon steel , such as aisi ( american iron and steel institute ) 1010 to 1018 series low carbon steel . the focusing bar 150 lies adjacent the exterior surface of fuel line 102 at a position substantially diametrically opposed from the magnet assembly 114 . the focusing bar 150 is believed to concentrate the magnetic flux into the fuel flowing through line 102 . the focusing bar also is believed to isolate the magnetic flux and substantially eliminate dissipation of the flux into the vehicle engine and chassis . to aid in securing the focusing bar 150 in place , and to provide additional shielding , the fuel conditioner 100 also includes a focusing bar receiving member or retainer 152 . the focusing bar retainer 152 includes a bar receiving portion 154 defining a cavity 156 sized to receive the focusing bar 150 . the retainer 152 has a skirt portion 158 extending outwardly from the bar receiving portion 154 . the skirt 158 lies against and frictionally grips the exterior surface of fuel line 102 . as shown in fig8 the leg portions 142 and 144 of the rubber shield 130 extend to surround at least a portion of the retainer 152 . note in fig8 for clarity additional space has been left surrounding the fuel line 102 . however , in practice , the legs 142 and 144 typically engage the exterior surface of the fuel line 102 and the retainer skirt 158 . the conditioner 100 has two pair of non - metallic tie straps , such as nylon tie straps 160 and 162 , to secure the assemblies 110 , 112 in place along the fuel line 102 . referring to fig1 and 11 , another alternate embodiment of a fuel conditioning apparatus or fuel conditioner 200 is shown installed on a fuel line 202 which may be as described above for fig4 . the fuel conditioner 200 is preferred for use with the heavier diesel - type fuels and more particularly for the larger diesel engines , such as those on the order of 5 . 8 liters in size , whereas the fuel conditioner 100 is preferred for gasoline - type fuels . the direction of flow of the diesel fuel through the conditioner 200 is illustrated by arrows , such as arrow 204 . the conditioner 200 may be installed as shown in fig9 between the fuel source 106 and the diesel engine fuel injectors 108 . the fuel conditioner 200 includes a pair of double fuel conditioner units , an upstream unit 210 and a downstream unit 212 , relative to the direction of fuel flow shown by arrow 204 . each of the double conditioner units 210 , 212 includes first and second fuel conditioner assemblies 214 and 216 , with the assemblies for the downstream unit 212 shown as units 214 &# 39 ; and 216 &# 39 ;. the upstream conditioner assemblies 214 and 216 each have a magnet assembly 114 as described above , with the north magnetic faces 120 of magnets 116 lying adjacent an external surface of the fuel line 202 at substantially diametrically opposed locations . the downstream conditioner assemblies 214 and 216 each have a magnet assembly 114 &# 39 ; as described above , with the south magnetic pole faces 122 of magnets 116 &# 39 ; lying adjacent the exterior surface of fuel line 202 at substantially diametrically opposed locations . each of the fuel conditioner assemblies 214 , 216 , 214 &# 39 ; and 216 &# 39 ; includes shielding means , such as a rubber shield 220 . the rubber shield 220 also serves to shield a magnetic field induced by the magnet assembly 14 into fuel flowing through the fuel line 202 as described above for the embodiments of fig2 - 4 . the rubber shield 220 includes a magnet receiving portion 222 defining a magnet receiving cavity 224 having an outer region 226 sized to receive magnet 116 or 116 &# 39 ;, and an inner region 228 sized to receive magnet 118 or 118 &# 39 ;. the rubber shield 220 has a skirt portion 230 with an outboard longitudinally extending portion 232 and an inboard longitudinally extending portion 234 . the skirt 230 also has first and second legs 236 and 238 for extending along the exterior surface of the fuel line 202 . referring to fig1 , the legs 236 and 238 are preferably of a length which allows the legs to overlap , shown as an overlap 240 of legs 236 and 238 of the diametrically opposing assemblies , such as assemblies 214 and 216 . the magnet receiving portion 222 has an inboard exterior surface 242 . as shown in fig1 , the skirt inboard portions 234 are sized so that when they are in abutment , the surfaces 242 of assemblies 214 and 214 &# 39 ;, as well as the surfaces 242 of assemblies 216 and 216 &# 39 ;, are separated from one another by a distance x . in the preferred embodiment , the distance x is substantially 3 / 4 inch . to secure each double fuel conditioner unit 210 , 212 to the fuel line 202 , at least three non - metallic tie straps may be used , such nylon tie straps 250 , 252 and 254 , which may be as described above for straps 160 , 162 or 32 and 34 . referring to fig1 , another embodiment of a fuel conditioning apparatus or fuel conditioner 300 is shown which may be particularly useful for smaller horsepower diesel engines , such as those on the order 2 . 2 liters in size . the fuel conditioner 200 shown in fig1 and 11 above is believed to be more suitable for larger diesel engines , such as those appearing in semi - trucks or tractors . the fuel conditioner 300 may be considered a hybrid double fuel conditioner unit , having components from both the upstream unit 210 and the downstream unit 212 of the fuel conditioner 200 . the fuel conditioner 300 includes a first fuel conditioner assembly 214 &# 39 ; and a second fuel conditioner assembly 216 as described above with reference to fig1 and 11 . in the fuel conditioner 300 , the south magnetic pole face 122 of magnet 116 &# 39 ; lies along the exterior surface of fuel line 202 in a position substantially diametrically opposed to a north magnetic pole face 120 of magnet 116 . since only one double fuel conditioner unit is used for the conditioner 300 , the longitudinally extending portions of the rubber shield skirt 230 are indicated as portions 232 &# 39 ; and 234 &# 39 ;, as neither is inboard or outboard as described above for portions 234 and 232 . otherwise , the components shown for fig1 are the same as those described above with reference to fig1 and 11 . regarding the spacing between two side - by - side fuel conditioner assemblies , such as 110 and 112 which are in abutment , and 214 and 214 &# 39 ; which are separated by a distance x , the performance tests have given varying results . preliminary tests were made of the fuel conditioner 100 with a 3 / 4 inch spacing between the conditioner assemblies 110 and 112 , rather than the abutting relationship shown in fig5 and 6 . these preliminary tests showed that a spacing of 3 / 4 inches to one inch apart yielded what was believed to be an optimal 1700 gauss magnetic field strength in a keyway portion of the fuel line located between the two spaced - apart assemblies , such as a keyway portion 302 shown for conditioner 200 in fig1 . in these preliminary tests , the strength of the magnetic field in the fuel line under each of the magnet assemblies was 1100 gauss , which was enhanced to the 1700 gauss reading in the keyway portion of the fuel line . thus , a 1700 gauss magnetic field strength was then believed to result in optimal fuel economy and was obtainable with the 3 / 4 inch spacing between the conditioner assemblies . in a later follow - up test , a 1700 gauss magnetic field strength , which is still believed to result in optimal fuel economy , was only obtainable with the two conditioner assemblies 110 and 112 in an abutting relationship as shown in fig5 and 6 . others in the art , such as chow mentioned above , overcharge the fuel by placing a magnet assembly as close as possible to the carburetor . as shown in fig9 it is believed that optimal performance of the fuel conditioner 100 , 200 or 300 may be obtained by locating the fuel conditioner a pre - selected fuel conditioning distance d from the fuel distribution system 108 . it is believed a fuel conditioning distance d of eighteen inches maximizes the fuel mileage and minimizes the fuel emissions of a vehicle equipped with the conditioner . both time and distance are believed to be required to realize the full effect of the ionization or polarization phenomenon caused by the magnetic field produced by the fuel conditioner . during this conditioning time , it is believed that this polarization phenomenon allows a match - up or mating of the available oxygen in the fuel , to promote more complete fuel combustion . regarding the decreased fuel emissions , very unexpected results were obtained when vehicles equipped with the conditioner 100 were tested by state vehicle emission test facilities . a fuel conditioner 100 was installed as described above on a 1982 dodge pick - up truck having a gross vehicle weight of 5300 pounds , and a six cylinder , 225 cubic inch engine burning conventional &# 34 ; regular &# 34 ; unleaded gasoline . during a standard state of california smog check inspection , the emissions were virtually nil , as shown in the emission test results table 3 below . table 3______________________________________emission test results maximum measured allowed result______________________________________2500 rpm test resultshc ( ppm ) 220 0 . 14co (%) 1 . 2 0 . 00engine rpm : 2619idle test resultshc ( ppm ) 150 0 . 13co (%) 1 . 2 0 . 00engine rpm : 738______________________________________ the hydrocarbon emissions in parts per million ( ppm ) were less than 0 . 01 % of the maximum allowed during the idle test , and less than 0 . 001 % of the maximum allowed during the 2500 rpm test . the carbon monoxide was 0 . 00 % in each test . furthermore , the test vehicle had no catalytic converter . the test technician was so surprised by these results that a fuel sample was taken to verify the use of regular unleaded gasoline . a similar test was conducted in the state of oregon on a 1989 gmc puck - up truck having the fuel conditioner 100 installed as described above . once again , the carbon monoxide at both idle and 2500 rpm was zero percent . the hydrocarbons at an engine idle of 900 rpm were 0 . 10 ppm , and ranged from 0 . 15 to 0 . 25 ppm at 2500 rpm . thus , it is believed that these emissions are superior , not only over conventional gasoline engines , but also over the emissions obtainable for natural gas - powered vehicles . tables 4 and 5 show the test results and the resulting improved fuel mileage for several selected passenger cars and diesel semi - trucks , respectively . table 4______________________________________type of car baseline with unit increase______________________________________1983 cadillac 19 34 79 % fleetwood1990 honda civic 31 49 58 %( 4 cylinder )( fuel injection ) 1989 honda station 30 51 70 % wagon ( 4 cylinder )( carburetor ) 1987 dodge caravan 26 40 54 %( 4 cylinder )( mitsubishi ) 1986 chrysler 26 42 62 % new yorker ( 4 cylinder )( mitsubishi ) ______________________________________ table 5______________________________________diesel over the road tractor - trailertractor without unit with conditioner increasenumber mpg mpg in mpg______________________________________ 71 3 . 52 4 . 92 39 . 8 % 82 5 . 00 7 . 28 45 . 6 % 142 3 . 79 5 . 49 44 . 9 % 180 4 . 06 6 . 22 53 . 2 % 184 4 . 22 6 . 37 51 . 0 % 187 4 . 50 6 . 10 35 . 6 % average : 4 . 18 6 . 06 45 . 3 % ______________________________________ as mentioned briefly above , due to the heavier nature of diesel fuel , the two double fuel conditioning units 210 and 212 were used for the fuel conditioner 200 on the diesel semi - trucks in table 5 above . the fuel conditioner 100 was used on the passenger cars for the test results shown in table 4 above . in both tables 4 and 5 , it is apparent that significant increases were obtained in the miles per gallon utilization of the fuel . as mentioned briefly above , overcharging of the fuel with too great of a magnetic force is believed to decrease the efficiency of fuel use by the engine . thus , for smaller sized engines , the magnetic field is preferably decreased . this can be done in several ways using the embodiments described above . for example , magnets having a lower gauss rating may be used in place of the 2 , 000 gauss magnets described above . alternatively , as shown in fig1 and 14 , a magnetically inert spacer 400 may be inserted within the rubber shield cavity in place of magnets 118 and 118 &# 39 ;, while otherwise , the components of fig1 and 14 may be as described above for fig8 and 11 , respectively . one preferred material for the inert magnetic spacer is wood , as shown in fig1 and 14 . for example as shown in fig1 , for smaller two -, three - and four - cylinder engines , on the order of 600 cc in size , such as may be found in small cars or motorcycles , the magnets 118 and 118 &# 39 ; of conditioner 100 may be replaced with wooden blocks 400 , while using magnets 116 and 116 &# 39 ; rated at 2 , 000 gauss . in this configuration , the fuel flowing through the longitudinal portion of the fuel line 102 beneath the assemblies 110 and 112 experiences a magnetic field of approximately 700 gauss . to decrease the magnetic field for smaller diesel engines , for example , 2 . 2 liters in size , the fuel conditioner 300 is preferred over fuel conditioner 200 . when constructed with 2 , 000 gauss magnets 116 , 118 , 116 &# 39 ; and 118 &# 39 ;, the conditioner 200 induces a 2400 gauss magnetic field in the fuel traveling between the assemblies 214 &# 39 ; and 216 . having illustrated and described the principles of my invention with respect to the preferred embodiments , it should be apparent to those skilled in the art that my invention may be modified in arrangement and detail without departing from such principles . i claim all such modifications falling within the scope and spirit of the following claims .