what oil weight should i be using in summer and winter? 1990 f150 5.0 alt 4x4 i live in utah so its hot in summer and cold in winter

 

5w-30 will be fine

 

Some use 10w-30 in summer then 5w-30 in winter

I use 5w-30 all year round

 

I use 15w40 synthetic, shell rotella, I had cam wear issues i a few engines, so i switched due to higher zinc additives in oil for diesel engines, 200 000 total miles on this engine, i got it at 50k, and still taking my abuse, i don t change it on any system of mileage, if i check it and it s still oil okay, when it doesn t look or feel like oil any more, i change it.
Check your owners manual, it has a chart recomending oil weight, by temperature range and usage, hotter, and more severe usage, thicker oil.

 

15w40 in all my trucks except the 75. but if i stay home the temp range is usually between 10-95 so nothing severe. no problems yet after 130k miles combined.

 

i ran 15w40 in my 77 power wagon but that has the 440. what do you think about running 10w40 summer and 10w30 winter? ps temp here has been 100+ lately and winter can either below 0 or 60 you just never know. and do you recommend any oil treatments like lucas?

 

iv never used oil treatment.

and 15w40 may he a lil thick for that cold of winters, in the summer it should be great. i would just run 10w30 in the winter.

 

I use either 5w-30 or 5w-40 depending on what's on sale.

 

I won't knock any shell product. Always ran 15w40 until I decided to go with 10w30 for my mpg project. I really like the shell synthetic though.