rach ide ▁( ear th - nut ▁or ▁pe a - nut ) ▁oil ▁( see ▁b iod ies el ), ▁and ▁worked ▁so ▁smooth ly ▁that ▁only ▁a ▁few ▁people ▁were ▁aware ▁of ▁it . ▁The ▁engine ▁was ▁constructed ▁for ▁using ▁min eral ▁oil , ▁and ▁was ▁then ▁worked ▁on ▁veget able ▁oil ▁without ▁any ▁alter ations ▁being ▁made . ▁The ▁French ▁Government ▁at ▁the ▁time ▁thought ▁of ▁testing ▁the ▁applic ability ▁to ▁power ▁production ▁of ▁the ▁A rach ide , ▁or ▁earth - nut , ▁which ▁grows ▁in ▁considerable ▁quantities ▁in ▁their ▁African ▁colon ies , ▁and ▁can ▁easily ▁be ▁cultiv ated ▁there ." ▁Dies el ▁himself ▁later ▁conducted ▁related ▁tests ▁and ▁appeared ▁support ive ▁of ▁the ▁idea . ▁In ▁a ▁ 1 9 1 2 ▁speech ▁Dies el ▁said , ▁" the ▁use ▁of ▁veget able ▁o ils ▁for ▁engine ▁fu els ▁may ▁seem ▁ins ign ific ant ▁today ▁but ▁such ▁o ils ▁may ▁become , ▁in ▁the ▁course ▁of ▁time , ▁as ▁important ▁as ▁pet role um ▁and ▁the ▁coal - tar ▁products ▁of ▁the ▁present ▁time ." ▁ ▁Despite ▁the ▁w ides p read ▁use ▁of ▁pet role um - der ived ▁dies el ▁fu els , ▁interest ▁in ▁veget able ▁o ils ▁as ▁fu els ▁for ▁internal ▁comb ust ion ▁engines ▁was ▁reported ▁in ▁several ▁countries ▁during ▁the ▁ 1 9 2 0 s ▁and ▁ 1 9 3 0 s ▁and ▁later ▁during ▁World ▁War ▁II . ▁Belg ium , ▁France , ▁Italy , ▁the ▁United