What if...High Mileage oil in GM V-8s

[NewGuy]

We have had a lot of discussion regarding the use of thicker 30 weight oils in GM engines. A recent thread discussing HM oils got me thinking about using it in my 5.3L engine. I believe that the 5.3L is a cast iron LS1 derivative (correct me if I am wrong).

Here is my thinking:
HM Oils are typically around 12 cst @ 100C vs 10.5 for CAFE compliant oils (dino and synthetic). Since fuel economy and newer formulation restrictions are not an issue....perhaps these HM oils are "optimized" for wear resistance vs. gas mileage.

Molakule indicated that the levels of additional seal conditioners would only be at a minimal level. Does anyone think that using these products in a relatively new engine would be an issue?

I would like to hear your thoughts and comments on this approach. A lot of people really like MaxLife and Castrol High Mileage, but what about for an engine with <50,000 miles?

 

[ToyotaNSaturn]

Go for it. I've been curious to see if the dreaded piston slapping goes away with an oil like Pennzoil's High Mileage 5w-30/10w-30. Seems like an obvious and economical "shoe-in" given the viscosity issue that you mentioned.

 

[TallPaul]

I think the Maxlife is listed at 10.5 cSt, but their Synthetic Maxlife is listed at 11.5. For you older type engine, you might like to get Citgo Ultralife high mileage 10w30 which is listed as 12 cSt and a UOA on this site showed SH zddp levels around 1200 ppm. Nice stuff if you can find it.

But check the product data sheets for each HM oil you consider for the viscosity and check their recommendation on use in newer engines. Generally they all should be fine in new engines, but I have only verified that with Maxlife.

 

[Triple_Se7en]

Castrol or Pennzoil HM would be my choice. If your money's tight or can't find the Citgo, do a 3K OCI experiment using Super Tech Syn-Blend High Mileage oil that's sold at Wally World.

 

[NewGuy]

I called Castrol and they tell me that a new car would not be harmed by the HM oils. Their 5W30 has a 12.0 cst viscosity (100 oC) and the 10W30 has a 12.1 viscosity.

Their tech data sheets also claim that the 5W30 exceeds API SM and ILSAC GF-4. I might give it a try during these warm summer months.

 

[TallPaul]

If you like Valvoline you can get around 12 cSt with about three 10w30 and two 10w40 mixed together. The Valvoline has 12-22 % PAO in it.

 

[Islandvic]

The Val HM oils state on the bottle it's safe for new and rebuilt engines.

I'm putting some MaxLife Syn in my new Honda 5.5hp pressure washer this weekend.

HM won't hurt new engines IMO.

 

[Ramblin Fever]

Some engines may not like it though; might be too thick. In which was the case for me with the 10w-30 Havoline HM oil in my 97 Rodeo WITH 140K mind you.