1. Stop at the red light.

2. Stop on the red light.
(Which preposition should we use?)

3. Turn slightly right.
4. This is a one-way street.
(Are both grammatical?)

5. Fill it up with regular unleaded, please.
6. Fill her up with regular, please.
7. Fill it up with the unleaded.
(Are the three the same? Which one is commonly used? Thank you.)

#s 1, 3, 4, 5, and 7 are correct and commonly used.

#6 is used in a slangy way in some parts of the US!

If you use #2, people will understand you, but it's not used much at all.

Also -- I don't know of any gas stations that have attendants. All the stations I've seen are self-serve -- so 5-7 are useless.

There might be a few full-service stations left in Korea!

http://www.arirang.co.kr/News/News_View.asp?nseq=152490

1. In the phrase "Stop at the red light," the preposition "at" is used. We use "at" to indicate a specific location or point. In this case, we are referring to stopping at the location of the red light.

2. However, in the phrase "Stop on the red light," the preposition "on" is incorrect. When talking about a traffic light, we don't stop directly on the light itself but rather at a location determined by the light, such as a stop line or intersection.

3. The sentence "Turn slightly right" is grammatically correct. It is a clear and concise instruction to make a small adjustment in the right direction.

4. The sentence "This is a one-way street" is also grammatically correct. It states a fact about the street, indicating that traffic can only flow in one direction.

5. The sentences "Fill it up with regular unleaded, please" and "Fill it up with the unleaded" are both correct and have the same meaning. They convey a request to fill a vehicle's fuel tank with regular unleaded gasoline.

6. The sentence "Fill her up with regular, please" is also correct, but it uses the pronoun "her" to refer to a vehicle. This is a more informal way of speaking and personifying the vehicle as if it is female.

7. The three sentences are essentially the same in meaning, with slight variations in wording and formality. In everyday conversation, "Fill it up with regular unleaded, please" is the most commonly used and understood phrase.