It is precisely when engines are claimed to be environment-friendly because they consume less fuel that we can not make any exceptions.
1	It	it	PRON	PERS-SG	_	2	nsubj	_	_
2	is	be	VERB	PRES	Mood=Ind|Number=Sing|Person=3|Tense=Pres|VerbForm=Fin	0	root	_	_
3	precisely	precisely	ADV	_	_	4	advmod	_	_
4	when	when	SCONJ	_	Case=Nom	7	mark	_	_
5	engines	engine	NOUN	PL-NOM	Number=Plur	7	nsubj:pass	_	_
6	are	be	AUX	PRES-AUX	Mood=Ind|Tense=Pres|VerbForm=Fin	7	aux:pass	_	_
7	claimed	claim	VERB	PASS	Tense=Past|VerbForm=Part|Voice=Pass	2	advcl	_	_
8	to	to	PART	_	_	10	mark	_	_
9	be	be	AUX	INF	VerbForm=Inf	10	cop	_	_
10	environment-friendly	environment-friendly	ADJ	POS	Degree=Pos	7	advmod	_	_
11	because	because	SCONJ	_	_	13	mark	_	_
12	they	they	PRON	PERS-PL-NOM	Case=Nom|Number=Plur|Person=3|PronType=Prs	13	nsubj	_	_
13	consume	consume	VERB	PRES	Mood=Ind|Tense=Pres|VerbForm=Fin	7	advcl	_	_
14	less	little	ADJ	CMP	Degree=Cmp	15	amod	_	_
15	fuel	fuel	NOUN	SG-NOM	Number=Sing	13	obj	_	_
16	that	that	SCONJ	_	_	20	mark	_	_
17	we	we	PRON	PERS-P1PL-NOM	Case=Nom|Number=Plur|Person=1|PronType=Prs	20	nsubj	_	_
18	can	can	AUX	PRES-AUX	VerbForm=Fin	20	aux	_	_
19	not	not	PART	NEG	_	20	advmod	_	_
20	make	make	VERB	INF	VerbForm=Inf	2	dislocated	_	_
21	any	any	DET	IND	_	22	det	_	_
22	exceptions	exception	NOUN	PL-NOM	Number=Plur	20	obj	_	SpaceAfter=No
23	.	.	PUNCT	Period	_	2	punct	_	_
