API SH 30 hello from new guy

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Hello,

I bought a 1997 Itasca motorhome with a L29 454 engine. Roller tappets 290HP 410Torque. I have been looking at the "Chevrolet Motor Home Chassis Service Guide" that came with the MH. The 'preferred' oil above 40F is straight 30 weight SH oil. I live in deep south Texas or as we call it north Mexico, so the under 40F time is nearly nonexistent. The engine has 43,000 miles and has been sitting for several years.

Straight weight oils seem to be hard to find any more and I'm looking for some advice.

I see that Tractor Supply has a straight 30 SH in their Traveller brand, I see Valvoline racing oil but it is pricey.

I have lurked here for years and you guys have a wealth of knowledge, I just hope I don't get overwhelmed.

I suppose I should post my filter questions in the filter forum.

IMG_20191009_215055502.jpg
 
SAE 30s are easy to find. O'Reilly stocks 2-3 depending on region. Walmart has Supertech as shown above. But no point in using that when 10w-30, 10w-40, and 15w-40 are readily available and you have more choices in brand.
 
I am going to be the dissenter here- straight 30 is old school, and you would be better served with a 5w30 or 10w30/40 . My 1997 Suburban with the same L29 7.4, 4x4 w 4.10 gears recommended 5w30. You could even go a bit higher to a 15w40, but personally I would never run a straight 30.
 
If it never sees temps under 40F 15W40 would be a good choice, although I would probably opt for something like TDT 5W40, or Delo XSP 5W40. Just in the event I decided to drive somewhere colder.
 
Id worry about the " sitting for several years" issue first. You are going to have many things to think about other than oil selection.

A decent HM 10w30 dino should do well. Just keep an eye on the Coolant and oil temp and idle oil pressure.

GM tappets have a designed bleed down rate for improved torque, you dont want to screw that up with incorrect KV100.

But this is a low HP BB not a mid HP gen one 350 so maybe OK.
 
Last edited:
Originally Posted by Chris142
Plenty of straight 30 here still. Odd that something that new says a straight weight is preferred. A 15w40 would be even better than a straight 30.



How so? Let's say for temps over 32F, what is the advantage?
 
Last edited:
Originally Posted by tundraotto
Higher oil film strength at temperature, better oil pressure, easier staring, to name a few


Higher oil film strength, yes! I agree.
Better oil pressure? Well, you're not wrong. Unless I wasn't getting any oil pressure, I don't know why I would want more. I get higher oil pressure when I start using higher HTHS oils, which is part of the first point.
Easier starting? Uh, not over 32F with 15w40.

[Linked Image]

graphs are kinematic viscosity (KV) vs fahrenheit.

Data from: https://wiki.anton-paar.com/en/engine-oil/
I understand that differences in blends should create some viscosity variability, but these are pretty close.

What I want to know is which one is the cleaner (deposits/varnish/carbon) between these two options?
 
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