6 Liter and 10w40

Blue Line Dave · May 1, 2004

I was wondering if I would mess something up if I put 10w40 Mobil 1 in my HD? Has any done this,is there any side effects to oil pressure or anything?Trying to quiet the CSK and all other noises. Any body?H Help please.

Butch 02 Denali · May 1, 2004

It is absolutly fine to run 10-30 synthetic. It's all I run in both my 6.0 and 5.3.

Butch 02 Sierra Denali

Blue Line Dave · May 1, 2004

Thanks Butch.Mobil 1 makes a new 5w40 for suv's and trucks think I might try it.

zorrro · May 1, 2004

I've ran Casteral or Valvoline 10w/30 in the Wife’s 5.7L for the past 40,000mi and it has been flawless (temp range 0-100 Deg). The manual recommends running 5w/30 as does my 8.1. I will run 10w/30 in the 8.1 once it's time for the oil to be changed. I do not really like multi-weight oils, and 5w/30 scares me. If I were just a little more ballsy I'd run straight 30 in everything...............Zorrro

8100HD · May 1, 2004

Running 10-w40 in my 8.1 with no problems...and yes it should help some with CSK...at least it did with mine.

Blue Line Dave · May 1, 2004

You guys are the best thanks for the reassurance I'll probably change the oil tomorrow.

Valsport · May 1, 2004

OK, you guys are getting your weights and viscosities mixed up. Blue Line Dave, you asked if it would be OK to run 10W-40 when your engine requires 5W-30. Then, Butch 02 Denali said it would be fine to run 10W-30, not 10W-40. After this Blue Line Dave you said "ok I want to try out Mobil's new 5W-40, which is neither 10W-40 like you asked about before, and not 10W-30 like Butch 02 Denali is referring to. 8100HD is the only one who has responded about 40 weight motor oil.

As for my answer, I'm not too sure whether or not either 10W-40 or 5W-40 is going to stop your CSK, and, I'm not positive whether or not its safe to run either 5W-40 or 10W-40 in the 6.0 liter engine.

Blue Line Dave · May 1, 2004

thanks for you reply Valsport,the viscosity is not realy an issue, Mobil 1 doesn't make a 10-40 anymore so I'm a bit in a pickle. I,ve tried 0-30 and 5-30 Mobil 1 and now I'll change tomorrow with 10-30 Mobil1 thanks for looking out for my truck though.

Valsport · May 2, 2004

no problem...I'd like to help with your situation. Are you experimenting with different oils for the sole purpose of tryin to stop your CSK? Honestly, I don't think any oil is going to stop your knock if 0W-30 didn't. When I switched from conventional mobil to mobil1 5W-30 I noticed a reduction of my CSK, but not termination of it. I'd try a good quality fuel system cleaner like the one Royal Purple offers.

GMCSierra04 · May 2, 2004

Just put in what the manufacturer says. The engines are desingned to run with a specific weight oil and thats what you should put in. Most new engines are running 5w30 because of its ease of pumping through the oiling system and better fuel economy are some benifits of the lighter oils.

422 SS · May 2, 2004

I ran 10w40 valvoline in my 6.0 liter van twice and won't do it again.As oil gets used it gets thicker and has a negative effect on fuel economy and performance.My mileage dropped a small amount and the engine felt sluggish after a couple thousand miles.I switched to 4 qts Pennzoil 10w30 and 2 qts of Mobil 1 0w40 and my mileage went back up and it feels more peppy.Oil will not cure CSK or any other mechanical defect.I ran everything from Mobil 1 0w40 to 20w50 dino oil with no difference whatsoever in oil burning or CSK with the 8.1 I used to have.Excessively thick oil hurts fuel economy,performance and will likely result in more wear than a thinner,more easy to flow oil.Unless it's a diesel or race engine with loose tolerances anything thicker than 10w30 in a modern vehicle is a negative IMO.

Richman · May 3, 2004

switched to 4 qts Pennzoil 10w30 and 2 qts of Mobil 1 0w40 and my mileage went back up and it feels more peppy.

Is mixing conventional oil and synthetic oil a "good idea"?

I was always told not to mix two different viscosities. I have never heard that your type of mixing is a good idea.

Shaners · May 3, 2004

Just put in what the manufacturer says. The engines are desingned to run with a specific weight oil and thats what you should put in. Most new engines are running 5w30 because of its ease of pumping through the oiling system and better fuel economy are some benifits of the lighter oils.

Exactly Right!!! Stick to the manufacturers recommended weight. Todays engines are designed with tighter tolerances and therefore the thinner oil is recommended for ease of lubrication.

A heavier weight oil can actually increase wear, especially when the motors are cold.

Chevyfreek · May 3, 2004

I run 10W-40 Amsoil Synthetic in my 6.0L and it runs just fine. It helps to quiet some of the noise from the motor between the CSK and valve ticking, which is common in these motors. I have experienced no adverse effects on gas mileage or how the engine runs. If you run a good quality synthetic 10W-40 you should have no problems.

422 SS · May 5, 2004

switched to 4 qts Pennzoil 10w30 and 2 qts of Mobil 1 0w40 and my mileage went back up and it feels more peppy.

Is mixing conventional oil and synthetic oil a "good idea"?

I was always told not to mix two different viscosities. I have never heard that your type of mixing is a good idea.

There is absolutely nothing wrong with mixing synthetic and mineral oil.Oil companies sell synthetic blend oils that are maybe 10% synthetic.I make my own "synthetic blend".