120K Mile 6G74 - Mobil 1 or Shell Ultra?

[Spetz]

I have narrowed down my oil choices to the above two.

The car:
120,000 miles
First 65,000 miles were at 9,000 mile OCI using I suspect dino oil
65,000-110,000 miles it had 6,000 mile OCI using semi synthetic
110,000+ miles (this is when I bought it) I have so far done 2 oil changes, first being Penrite fully synthetic 15W50, second Castrol Edge 5W40.

The usage:
Car is used during weekends only. Often takes 200 mile long trips. No short trips, mix of medium traffic and highway driving.

The engine has varnish which I was hoping to slowly clean, so I already have Shell Ultra 5W40 oil.

My question is will the Shell Ultra help varnish clean up?
Am I better off using Mobil 1 oil?
Which oil will offer the best protection and longevity for my motor?

I plan on annual or 9,000 mile (15,000km) OCI, whichever comes first.

 

[spasm3]

Either should work well. If you can get mobil 1 high mileage, it claims more cleaning ability than regular mobil 1.

 

[Spetz]

Is cleaning something that I should be aiming towards?
Would HM or Shell Ultra slowly get rid of the varnish?

 

[GaleHawkins]

Just started using Mobil 1 high Mileage 10W-40 in the 2003 5.3L GM engine the last two oil changes after having no oil pressure on start up when hot that went away after adding 8 oz of Seafoam to new dino oil for 160 miles. Well I went with the 10W-30 version the last oil change. Never had an engine do that before but that generation of GM engines did have some oil pressure relief valves sticking issues per the web and youtube videos.

 

[hpb]

Honestly, I doubt you'll see much improvement regardless of what you use. It's done near on 200,000km, any varnish is pretty well stuck there now. Is it really that bad, have you had the rocker covers off? You might be worrying somewhat unnecessarily.

If it runs quiet and smooth, I wouldn't sweat it. Is the car an old Magna? If so, I'll bet it's one of the only ones getting such expensive oil!

Another question, why do you speak in miles rather than kilometres? I know this is primarily a US site, is it to save the majority having to do the mental math? Not a criticism, just asking as I'm very new here!

 

[Spetz]

Yes it's an old Verada (2003).
It runs quiet and smooth, the varnish has no impact on it and it's not horrible. The best way I can describe as to the driving factor behind wanting to get rid of is an OCD like urge.

As for using miles, it's because it seems to be the accepted measurement on this site and to save any confusion.

 

[hpb]

Fair enough, thanks for the clarification re miles vs kilometres! And yes, I fully understand the OCD like urge...it'll be interesting to see if you have any luck cleaning it up. Veradas/Magnas of that era are good cars, it's a real shame the 380 didn't achieve the success it deserved.