What oil viscosity?

1989 thunderbird with 108000 miles. Should i use 10/30 or 20/50? Its winter time, and here in Oregon i have a high temp of 45.What oil viscosity?
In this weather, I wouldn't recommend anything over 10W-30 SAE. Even with 108K, this isn't all that bad for that old a car.


In the summer time, if your mechanic recommends 20 - 50 SAE it wouldn't hurt, but 20 - 50 SAE in the winter time runs the risk of flooding the engine bearings.


Just be certain that you use a good quality motor oil and you will be fine.





Good Luck and Merry ChristmasWhat oil viscosity?
I'd stick with the 10W-30. It's better to be safe than sorry. Short and simple. Hope I was of some help.
i have a 1988 olds and i use 10w30 and its got more miles then yours.the viscosity is the thickness of the oil.
20-50w for your situation.
Ask your mechanic what is reccomended.With a high mileage engine maybe higher viscosity could be reccomended.
Running thick oil in A high mile vehicle can do more damage than good.It takes longer for the thicker oil to reach critical engine parts


You should run the Manufactures recommend viscosity for the life of the vehicle 5w-30 for summer 10w-30 for winter.





Owner operator E-Z Lube
I'd recommend 5w-30.....


much better cold start up flow at lower temps over 10w-30...


10w-30 in the summer..... not the other way around.


I wouldn't use 20w-50 even if recommended to..... unless the engine was using alot of oil.... and or leaking alot of oil...... and or had very low oil pressure (10lbs per 1000 rpm)
Only use the heaver oil if you have to ad oil between changes. If you plan to start the car at or below freezing you will need the lighter oil anyway.
oil viscosity is the thickness of the oil. 10w-30 the ten is the winter weight when started up, once @ normal operating temp. it is then 30. With the amount of time and miles on your vehicle i would highly reccomend using a higher viscosity oil such as 10w-50 or something near. Reason being, with the higher mileage there is obviously much more wear on the internals such as the main bearing, crank journals, connecting rods, etc. to compensate for these larger clearences a thicker oil can be used. Also from experience the valvoline MAX LIFE oil does indeed work much better on older cars also due to the additive package.