YOU SAID:
I will let you use my car
INTO JAPANESE
私はあなたに私の車を使わせます
BACK INTO ENGLISH
I let you use my car
INTO JAPANESE
私の車を使わせて
BACK INTO ENGLISH
Let me use my car
INTO JAPANESE
車を使わせて
BACK INTO ENGLISH
Let me use a car
INTO JAPANESE
車を使わせて
BACK INTO ENGLISH
Let me use a car
That didn't even make that much sense in English.