[room217au]

This is the chassis file for the 6×4. Note the line: tank_size: 1600
Open Part 1 file and look in def\vehicle\truck\ken200\chassis\6×4.sii
The 1600 value is in litres, so gallons are about one-quarter of that. Change ONLY the tank_size value. Touch nothing else.
Save the file. The archive should automatically save the file change too.
All chassis files work the same way.

SiiNunit
{
accessory_chassis_data : 6×4.ken200.chassis
{
name: “@@chassis@@ 6×4”
price: 26000
unlock: 0

info[]: “6×4”
info[]: “800 + 800 @@unit_l@@”
icon: “ken”

model: “/vehicle/truck/k200/new/truck.pmd”
collision: “/vehicle/truck/k200/new/truck.pmc”

residual_travel[]: 0.12 # 1st axle
residual_travel[]: 0.08 # 2nd axle
residual_travel[]: 0.08 # 3rd axle
tank_size: 1600
adblue_tank_size: 400
variant: chs_6x4
look: default

defaults[]: “/def/vehicle/truck/ken200/accessory/trlr_cables/stock.sii”
defaults[]: “/def/vehicle/truck/ken200/accessory/box_steps/shape2.sii”
defaults[]: “/def/vehicle/truck/ken200/accessory/bamper/shape1.sii”
defaults[]: “/def/vehicle/truck/ken200/accessory/bak/shape1.sii”
defaults[]: “/def/vehicle/truck/ken200/accessory/krilo/shape1.sii”

suitable_for[]: “sleep_a.ken200.cabin”
suitable_for[]: “sleep_b.ken200.cabin”

extended_shadow_texture: “/vehicle/truck/k200/textruck/shadow_6x4.tobj”
extended_shadow_intensity: 0.97
extended_shadow_fadeout_start: 10
extended_shadow_fadeout_length: 0
ui_shadow: “/vehicle/truck/k200/new/ui_shadow_6x4.pmd”

powered_axle[0]: false # front axle
powered_axle[1]: true # rear axle
powered_axle[2]: true # rear axle

kerb_weight[0]: 7100.1
kerb_weight[1]: 1900.1
kerb_weight[2]: 1900.1

}
}