Safe to change to synthetic

[brandon7777]

Can anyone tell me if Z-max every 6000 miles with a 10w30 oil increase performance or save gas. I have a 2001 chevy silverado with a 4.8L. Z-Maz supposedly gives you a 150000 mile warranty. And they will fix your engine if anything will go wrong.

[jumpingjack66]

Changing to synthetick at hy milage seems like a waste of time. Synthetics atrributes are that it prevents ware so using itearly in a engines life would be best. I started mine at 15,000 miles with mobile one and an upgraded filter. I run my oil a little longer, and i figure with everything working against these gen III engines it will need all the help it can get.

[Puna]

Castrol..........good enough for John Force.......good enough for me

[gschretter]

My 87 F-150 with 350,000 still does not burn oil.
20W-50 with Motorcrafts filter.
Now the internal parts have burnt oil all over it but it still does not burn oil.

[pcollins1]

brandon7777 dont use the z max or slick 50 they are to expensive. and you take it all out when you change the oil even the cheapest synthetic works better than z max and like some one stated earlier you can run synth oil 12 to 24 thousand miles. royal purple and amsoil are the top 2 and if a little does leak use some bars leaks, if the bars doesnt fix it something needs to be repaired engines dont consume much oil (minimal) but i would stay with one brand due to different detergents in the oils (synthetic or regular)

i use royal purple in my 81 chevy 350 and i love it,

[borninski]

Originally Posted by silveradoman

I also use CAstrol 10W-40, the thing is if I use 20w_50 in the summer am I just hurting the mileage? It is very common to get 100 degree plus heat in the summer everyday over here and everybody I talk to down here says 5w-30 will break down very very easily, what´s your opinion?

I would never switch to any higher weight oil. I mean, if your truck has 250,000 miles on it and leaks oil badly I would probably go with a 40 or evenb 50 weight oil. However, newer trucks were designed SPECIFICALLY for a CERTAIN WEIGHT oil to be used. For my 1997 c1500 5.0, it is 5w-30. (btw, I have never leaked oil). One oil change I used Valvoline MaxLife 10w-40 with some STP oil additive thinking it would recondition some worn seals and help my truck run better for the long haul, but all it did was give me very poor gas mileage (about 1.5 mpg drop). Now, I am back to religiously changing my oil (about 2,000-2,500 max., I can do this because I get free oil and filters at the shop I work at) and using 5w-30. The mileage is good again and I have even used oil flushes (engine flushes) after draining the oil to get the sludge out and my oil looks like it came out of a brand new car!
Like I said, I would definitely go with the manufacturer suggestion on oils because I am sure they knew what they were doing when they built the car. Furthermore, a heavier weight oil will cause your engine to possibly not start (or at least not start as easy) in cold winter temperatures. The lighter weight oil (5w-30) is the recommendation because it is good in extreme temperatures like winter cold.