Shell Formula C2500 Suburban

[quick_16]

I have drove this 1998 C2500 (3/4 ton) Chevy Suburban sense new... 170k miles. Back and forth to work and tow a 9500lb 28' TAG Trailer to the race track every other week. Original 5.7l Vortech does not smoke or leak a drop.

I think it likes this 5w30 thin oil like the wifes Honda did.

I'm think 5000k is about the correct interval

 

[UncleS2]

Looks good overall, especially for a full-sized V-8 with over 170,000 miles on bargain-basement oil. Formula Shell strikes again!

I have FS 10w30 SL/GF-4 in my car now for Auto-RX rinse phase #2.

Questions:

this interval: Formula Shell SL or SM? If SL, GF-3 or GF-4?

Previous intervals, from Jan 05 & Oct 04: what oil was that?

Thanks for posting- with another 40 qts of Formula Shell on deck, I'm always interested in seeing UOA's.

*Edit*: I'll show my ignorance here- what's a TAG trailer?

*Double Edit*: Just read the new UOA on your Honda with FS: makes me glad I used Supertech for 2 of my 4 Auto-Rx cycles, that leaves me two more fills of Formula Shell!

 

[quick_16]

Thanks
The bottle says SL and GF-4
10/11/04 and 1/30/05 was Chevron 10w30
Both had TBN is the 1.5 range
I have no idea what TAG stands for and I've had them for over 20 years. For some reason my ISP is not leting the pic files hsow but if it comes back here's what it looks like.

 

[TooSlick]

Did you have any mechanical work done on this engine prior to 140k miles - possibly to fix a leaking intake manifold gasket? There are past traces of Na and K, which have since tapered off....

TS

 

[quick_16]

TS Yes at 90k I had the intake gasket replaced. GM design defect that owners have to pay for.

I also had Crane Roller Rockers on from 50k to 110k with no issues.

 

[Ray H]

Any oil formulation that meets GF-4 is really an SM oil. These are NOS bottles in which the new formulations were issued prior to the API's official November 30, 2004 SM retail introduction date. ("SM" actually could be displayed - just not in the API "donut".) ILSAC carried no such restriction, so savvy buyers were able to jump the gun if they realized the presence of "GF-4" anywhere on the bottle labeling was the key to getting the good stuff earlier. I found "GF-4" being displayed as early as mid-September '04 in some brands. Another key in UOAs are zinc levels under 800 ppm and phosphorus levels under 600 ppm.

 

[UncleS2]

Good to know. When I asked about that several months ago("Does GF-4 = SM?"), was told that it wasn't necessarily so. The Formula Shell additives do match your criteria though.

Of the 40 qts of FS on my shelf, 5 or 6 are 5w30 GF-3. I plan to run one full 4.5 qt fill from that, with LC, for about 3K. After that, I'll use 1/2 qt at a time at oil changes to top off 4 qts of Shell 5/10w30 SL/GF-4.

Or maybe not- tempted to use 1 or 2 qts of BobZoil 5w30 SL/GF-3, rest Formula Shell. Or maybe mix in a qt of Havoline SM. Or maybe...