I own a used 2000 Mercury Marquis LS with 70k miles.

I have continued using 5w-30 oil on oil change and Regular Gas as the manual indicates.

I am curious. What grade of oil and gas are all of you using in your Marquis' with similar mileage?

 

I'm driving a 2001 Grand Marquis, pushing 165,000 miles. I use the recommended oil 5W-30 and regular gas. There's a reason the engineers and manufacturers recommend a specific weight oil. Lighter weight oils are used for engines with tighter clearances and ensuring that the oil gets to your vital engine parts quickly especially on cold starts. Using a heavier oil would only defeat the purpose, so I'm sticking with all the recommended specifications.