10w30 or 5w40

[QMartinez]

I am going to be changing my oil and I'm switching from delo 15w40 to either rotella 10w30 semi syn at 16 a gallon, or mobil1 5w40 full synthetic for 5.00 a quart. I'm leaning towards the mobil1 but with all the threads I have read about oil shearing is the 10w30 going to be better? It has been down to 5 degrees some nights. I do plug in but which oil will be better for cold starts and protection?

[6.0DJ]

Had a 95 7.3 and ran 15w40 all year in it and I now own a 07 6.0; still running 15w40. No Problems yet and it is -30 right now with the wind chill. Get a block heater.

[WildStyle]

Windchill doesn't effect vehicles...

At our dealership we run 15w40 in the summer months and 10w30 in the winter months.

[e99f2506sp]

I run 5w40 year round. Never have to plug in (fired right up with no rhomping or anything yesterday morning at 4º after 1min of glow plugs)

15w only offers protection down to 32º or so, so if you see temps any colder than that you're just hurting the engine and putting a ton of strain on the oil system. (example, go suck some molasses through a straw)

30w only offers protection up to 90º or so, so if you see temps any warmer than that, your just asking for trouble.

5w40 syn covers all of your bases. the 5w for cold temps, and the 40w is the same as the 15w40 so there is no question it will work.

[diablos30]

Originally Posted by 6.0DJ

Had a 95 7.3 and ran 15w40 all year in it and I now own a 07 6.0; still running 15w40. No Problems yet and it is -30 right now with the wind chill. Get a block heater.

wait until the injector stiction starts, you'll wish you hadn't run that mud in a 6L.

[jd4010]

I'm running Amsoil 15-40 in my truck....year round. But then again, it's really only used during camping season (April to Oct). However, on my next change I'll be going to 5-40. The 5-40 will give me the protection in the hot days of hauling our 5er but I'm also hearing that I may see an improvement in MPG. Also going to change from Amsoil to Rotella...as the Rotella is less expensive and still a very reputable product.

[QMartinez]

I plug my truck in every night and it starts fine with the delo15w40 but I can't plug it in while I'm at work. So I'm thinking 5w40 might be a good choice.

[QMartinez]

Does anybody notice more oil consumption with the synthetic? My truck doesn't burn any oil between oil changes. I've noticed in my motorcycle and my wifes car which both use synthetic they tend to burn alittle more oil.

[13_focht]

Running 15w-40 year round and not plugging in is only for people with no respect for their truck. I run 15w-40 most of the year but once november hits 0w-40 full synthetic goes in and stays till april in my 01 7.3L. My 08 6.4L gets 0w-30 full synthetic year round. Both trucks get plugged in over night as soon as it starts freezing, during the day when it gets into the -30c. The cost of oil and plugging in is nothing compaired to a rolled bearing or a split cylinder. I bought a truck from a guy like e99f2506sp once and spent a fourtune fixing that poor 7.3L.

[PGreenSVT]

5wXX is the way to go any time. In the winter 5w30 is a real good choice and in the summer 5w40. Schaeffer 9000 full synthetic is available in both weights at very reasonable prices.