5W30 or 10W30 for winter?

My owners manual says I can run either as long as it's 0 degrees or above. The average temp where I live is about 20 degrees. I've heard that there's very little difference between the 5 or the 10, and I should stick with the 10 all year. Your thoughts?

1998 Z71 5.7L

The 5W30 oils are better for colder climates because they act as a 5 weight oil when cold and as a 30 weight once warm. So the oil is thinner when it is still cold providing protection whle the oil is cold but allows it to be thin unlike heavier oils that will not thin out till they warm up. This is the way i was explained 5W30, 10W30 ect means. It is either 5 or 10 weight when it is cold and after it warms up it acts as a 30 weight oil. I could be wrong, but like i said that is how it was explained to me. If anyone out there actually knows ,or if what i heard was right please let me know. thanks,
Ken

From what I know, you've hit the nail on the head Kenny. I always run 5W30, you never know when you might need that little lower viscosity and price is pretty much uneffected. What do you do want to pay attention to is that you try and stick with a specific type of oil. It's been known that changing oil types too dramatically will cause the engine to burn more oil.. not sure if its true. Just trying to be safe. Also, synthetics are supposed to last longer. It doesn't break down like the conventional oil. If you don't change oil as often as you should it'd be wise to look into synthetics as they will last about twice as long.

My owners manual says I can run either as long as it's 0 degrees or above. The average temp where I live is about 20 degrees. I've heard that there's very little difference between the 5 or the 10, and I should stick with the 10 all year. Your thoughts?

1998 Z71 5.7L

Greetings GMC,

My 2004 Silverado 1500 has the "Use 5W30 Only" printed right on the oil fill cap. I figure they do that for good reason. Because my truck is new and I'll do most all the oil changes (except cold winter changes once a year) - I bought 4 cases of Havoline 5w30 oil. This way I know I'm using good oil (no Pennsylvania oils), its consistent brand and consistent weight. Then I bought a half dozen Purolator oil filters and a quart of Silick 50. That should do it for me for awhile.

In the past - I never used a 5w30 in the summer in my past vehicles (always 10w40 or 15w40) - but I figure if Chevy wants me to use 5w30 in my new truck - thats exactly what I'll do. :-)

White Lightening

gmc- Like Kenny and Brandon said, 5w30 will flow better in the cold, but has about the same hot viscosity as a 10w30. For really cold temps, synthetic oil will flow even better.

White Lightning- The Havoline and Purolators are good choices, but I would return the Slick 50 right now. A new engine shouldn't need any additives, and I suspect the Slick 50 won't do anything but lighten your wallet. The links below suggest that it could have some negative effects, too.

http://theoildrop.server101.com/cgi/ultimatebb.cgi?ubb=get_topic;f=5;t=000521
http://theoildrop.server101.com/cgi/ultimatebb.cgi?ubb=get_topic;f=5;t=002557

Here n the summer the temperatures can soar way above 105°F, do you switch to 40 or 50 grade oil to protect the engine?

Here n the summer the temperatures can soar way above 105°F, do you switch to 40 or 50 grade oil to protect the engine?

Greetings Silveradoman,

Personally - I have always used good quality 10W40 or 15W40 or 20W50 in the summer in my engines in Wisconsin and 5w30 or 10w30 in the winter. However Chevy has it in my manual and on the oil filler cap in the engine compoartment - 5w30 oil only. So that is what I'm going to do. 2004 manual and 2004 Chevy Silverado Vortec 6000 high output engine.

White Lightening

well,,, i went of the rocker and spent some cash last week i did the ROYAL PURPLE oil change and couldnt be happier guess what the morning knock?????? it's fucking gone? i also used the k@n filter so the oil was like 90bucks cdn for a case of 12 and the filter was like 16 bucks at crappy tire, i split the caes of oil with my brother and he said his top end tick is gone too he has the 350 vortec i have the 5.3 vortec the oil is 8bucks a liter or 650? ithink if you buy the case well worth the buy CHECK IT!

Hmm..Royal Purple. I oughta try that.
I've been using Valvoline, until my last change, I used valvoline "High Mileage"...hope that dont screw nothing up.

Mobile one 5w30 and AC filters in everything. Techron stopped the piston slap in the 5.3 and "almost" fixed the gas gage in the Vette.

royal purple has a web site check it out! i think it's worth every penny and ill continue using it now, iam even going to throw some in the diff and my hog!

10W40 oils are a big no no and will void the warranty. Check with your dealer service rep. I cant remember the exact reason but I think it has to do with tighter engine tolerances. If it ain't in the book don't use it.

Since we're on the subject I've got a quick question about using synthetics or even royal purple. I've been told that switching to synthetic on a higher mileage vehicle could lead to leaks because of the removal of buildup and deposits around the seals on the engine. My Z71 has close to 98,000 miles on it and i've been a little hesitant about switching to royal purple. Do you think 98,000 is too "high mileage" or should i be alright switching?

well if you did your oil change when recommended and you didn't let it get all black i cant see carbon deposit's being a problem, that occure mostly if you dont change your oil often than you'll get a build up, so i'd anytime is a good time to go to synthetic!:naughty:

Since we're on the subject I've got a quick question about using synthetics or even royal purple. I've been told that switching to synthetic on a higher mileage vehicle could lead to leaks because of the removal of buildup and deposits around the seals on the engine. My Z71 has close to 98,000 miles on it and i've been a little hesitant about switching to royal purple. Do you think 98,000 is too "high mileage" or should i be alright switching?
I switched a Dodge Caravan at 60k with good results but I wouldn't do it at 98k. True, if you've maintained it well, there should theoretically be no problem but I've heard too many horror tales.

Since we're on the subject I've got a quick question about using synthetics or even royal purple. I've been told that switching to synthetic on a higher mileage vehicle could lead to leaks because of the removal of buildup and deposits around the seals on the engine. My Z71 has close to 98,000 miles on it and i've been a little hesitant about switching to royal purple. Do you think 98,000 is too "high mileage" or should i be alright switching?
--well i did the switch at 120k and my brother did it at 235k no probs yet----

10W40 oils are a big no no and will void the warranty. Check with your dealer service rep. I cant remember the exact reason but I think it has to do with tighter engine tolerances. If it ain't in the book don't use it.

Well.... We get 110°F weather in the summer, stores around here don´t even sell 5w30 or even 10w30, in summer they sell 20w50, people run their cars without a thermostat also. Tem minutes on the road and your oil pressure will be down do 5, and your water temp will be in the middle of the gage, I will switch to synthetic next oil change and will probably try the 10w30.