My Lr3 hse HIT 100K miles. I had been putting valvoline duralube (semi synthetic) in it but wondering if those high mile oils are better. STP has a high mileage 5-30w.

Is it best to use the high mileage oils or just stick with regular 5-30. I would get full synthetic but heard it can sometimes cause gasket leaks if you go from regular oil or semi to full synthetic.

 

Synthetic doesn't cause leaks, it is just more likely to find existing leaks.

I've always sworn by Mobil1 and Royal Purple

 

I don't have any existing leaks, I am talking about going from NO leaks to having leaks. Read quit a few stories on that. Its harder on seals.

 

 

In all the years, I never heard any claim that synthetic is harder on seals. If anything, I would be better for them since it contains less distillates.

Anway, I use Castrol GTX Edge? Something like that. Synth-blend. Very inexpensive compared to Mobile 1, which I use on my V12 BMW because of "black death" from Dino oil. I dont think the 4.4 suffer from such an issue.

 

I have been running conventional oil since the beginning and I am at 250 K miles with no problems or loosing oil in between changes etc.etc. The only problem I might have will be in two months during road trip as I will have to change oil somewhere in UT, Nevada or Northern Cali depending on our itinerary.Whereas if I run synthetic it would be enough to run the entire trip with average changes between 7500 miles.So yes, running full synthetic makes sense in many cases. i debated that idea to switch when I was at 80 000 miles and was advised by many not to, as it was kind of to late to switch.
As you are on semi synthetic, I don't think switching to full synthetic would be a big problem, but again, i am not an expert. I would stick with whatever you have been using just to be on the safe side.How often do you change that oil ?

 

that's what Im saying.

Synthetic does not cause damage to seals/gaskets. It can make existing damage noticeable where conventional doesn't because synthetic is able to leak from gaps that conventional wont.

Unless your gaskets are from the 80s or earlier, Synthetic is safe and doesn't damage anything

 

Mine used conventional Castrol GTX 5w30 its entire life (dealer serviced before me) so I continued.
I just change it every 5k now.

My analysis at 115k was excellent, so I am not changing. I am at 140k now. Will do another analysis in 5k or so.

Get yours analyzed. Don't switch based on a guess or marketing or what others do. Do what yours needs based on real data.

 

I change based on when the vehicle tells me. Changing oil too often can result in long-term engine damage from additives in the fresh oil that dont get time to break down between short intervals and thus build up. There is some tech data and write up online about it. But really you would have to own the vehicle for 200k and be changing it every 3k or less. In this day and age, no one should be changing oil any less than 5k miles. Or by any specific date. Those oil change places are the biggest scam when it comes to intervals/dates.

Keep in mind one of the most wasteful institutions on the plant, the US military, actually does oil analysis on vehicles before deciding if they need a change. The result is most Hummers, for example, ran oil for over 12k before a change. This is first hand info I got from a buddy who's job was literally to do oil changes on military gear and send out samples for analysis. So even they did not change oil for the sake of changing it based on frequency, etc. My BMW can go about 10k between changes on Mobile 1. Also your oil volume will dictate frequency. My BMW holds 8 quarts of oil. The Rover, for its engine size, has a high capacity also at 8 quarts because of the deep sump. My Mark VIII only used 6 because of a shallow pan design, so changes were around 4k miles.

 

Analysis? What is that someone tearing the motor apart to look at the rings? or a simple compression test?