In my '96 5.9 the owners manual says to use 10w30 oil. I frequently get in the truck and go on a dime because of being on a fire department. I know that I should let the warm up a while, but that just isn't possible. I have a block heater, but I know it doesn't keep the oil from getting thick.

Would running 5w30 oil be a better for the engine? Once it starts warming back up, I would switch back to 10w30.

 

i use 5w30 year round and i have no problems...

 

Use the recommended grade oil for you climate. I have ALWAYS driven my vehicles away just as soon as oil pressure comes up. I figger they warm up faster being driven, than sitting there idling. (not to mention, idling in my driveway, I am getting 0 miles per gallon....... I can't afford to let my V-8 sit and idle.) I have over 150,000 miles on ALL of my vehicles. Some over 200,000.

 

i never take off and go....i always let it run at least a minute, then i shift into neutral for about 30 seconds then ill take off.....if its real cold i let it run so when i jump in its nice and toasty.

 

Well you ask the million dollar question... our second gen's are getting old so the internals develop a little slop. Your question begs an answer to the question: "do you want to be near original manufactures specs for oil weight, before or after shear?" Shear is the break-down of the long molicule chains used to make multi weight oils. What happens is the moliclues heat up and streighten out versus being curled up in a ball when cold. The long moliclues get cropped off when they pass through the pistons and other areas of stress. After driving 50 miles with your 10W-30, your high end is more like a 25 weight because of shear. At 2,000 miles it may be a 20 weight oil.

As a former CAM2 Oil sales rep, I will pass along what my tribologist told me... use a 40 weight in an engine that requires a 30 weight; when it shears, it will be close to a 30 weight. One hundred miles down the road, no oil will meet spec any longer.

I run a 5W-40 in the winter and a 15W-50 in the summer towing months. Obviously I am running oil speced for diesel. Diesle oil meets gasoline specs with the benefits of a higher TBN to nuetralize gas blow by and acids that develop. Go to wally world, Shell Rotella T6 5W-40 Full Syn is about $20 and Mobil One Turbo Deisel is about $23.

Mobil's 15W-50 is about $23 at wally world. Hope this helps.

 

While this may be true I am sure the manufacturers compensate for it when they put oil info in the owners manual. The engineers that design these motors are not stupid people. Changing the oil at the proper intervals has far more of an effect on engine life than the proper weight oil as long as it isn't way off.

 

Oil is a very hot topic! I'd just stick with what the manufacturer specifies. Simple as that.

I wouldn't run 15w-50 in my engine...

 

I run 10w30 summer and 5w30 in the winter, I also agree with jstmoto I wouldn't run 15w50 even if it was free, I would go by manufacturers specs

 

You'll have NO PROBLEMS running 5w30 in colder climates (or really in warmer ones for that matter) in an engine that specs 10w30 .

The viscosity is the same at running temperature and a little thinner before the engine warms up in winter. As a result, the oil will flow a bit faster and be easier on the oil pump at startup on cold days...

 

My owners manual suggest 5w-30 when temps will not be above 60 degrees and 10w-30 when they will. As it just got cold I switched to 5W-30.