Just wondering what engine oil would be the best for 4.9 with 143k miles. It is not necessarily driven daily; I do several short-distance driving per week, and about 1-2 hrs of driving on weekends. It will be winter here in Minnesota soon (read: very cold), so what brand & viscosity would be the best (if other than 10w-30)? Any input would be appreciated.

When I lived in Ohio I never used thicker than 5w-30. The slightly thinner viscosity helps to get the oil pumping when it's cold in the pan.
You might also want to think about going 1 heat range hotter on your spark plugs if you only make short trips.

When I lived in Ohio I never used thicker than 5w-30. The slightly thinner viscosity helps to get the oil pumping when it's cold in the pan.
You might also want to think about going 1 heat range hotter on your spark plugs if you only make short trips.


uh... what do you mean by 1 heat range hotter on spark plugs (I'm not too bright a mechanic here, haha). But, thanks for your input on thinner oil for winter use; I also thought about that in the past, but I always thought I should stick to manufacturer suggested 10w-30. Also, my idle seems rougher when the car is not level (and sounds funny, as if it's not getting enough lubrication throughout); does this happen in any other 4.9 cars? I know these engines have rough idle by nature, but it seems distinctly worse when on steep grade.

When I lived in Ohio I never used thicker than 5w-30. The slightly thinner viscosity helps to get the oil pumping when it's cold in the pan.
You might also want to think about going 1 heat range hotter on your spark plugs if you only make short trips.

That's why I use platinums in my cars, they get up to the optimum operating temp supposedly in seconds to burn off excess fouling, and forms a more complete burn for better combustion, and better fuel economy. The owners manual for my 1991 4.9 says never use 10w40, "the engine will run best with 10w30. However you can use SAE 5w30 if it's going to be colder than 60f before your next oil change. When it's very cold, below 0 F you should use 5w30."

I plan to use 10w30 synthetic because synthetic stays fluid even at -50. And I would still be keeping with the recommended viscosity for the oil.

Oh ya, I'm getting 18-20 mpg city and up to 35 on the highway!! Perhaps low mileage has something to do with this?