jgm

I have a 1990 Lexus LS400, it runs fine and I drive it to work 60 miles round trip 3 days a week and 100 miles 3 days a week when I go to another town to put in some extra work, so that 480 miles a week on top of the ones I put on driving around my city.

What is the best maintenance service I can do for it to keep it going strong? I have noticed it is now leaking oil, not sure from where. Is there a good stop leak additive?

What kind of oil should I use 5w-30 or 20w-50, or high mileage but what grade?

Last week I replaced the radiator, air filter and thermostat. I also noticed the idle has gotten louder when I start it up in the morning.

How many more miles can I expect it to go?