You are sorta twisting my words here. What can you rely on then? You have to either take things into your own hands or believe the marketing hype. You have to make SOME decision when you grab xx oil over yy.

For a given price point, I tend to purchase the one that I can get fairly easy (I'm not going to jump though hoops and drive all across town looking for oil) and seems to test out the best on our motors. I'm sitting here at WalMart starting at Mobil 1 or Penzoil Plat for about $23 / 5 qt container. I'm going to grab the PP.

 

Sorry that wasn't my intent. I do exactly what you do when making my oil purchases. Walmart FTW!

 

I just bought German Castrol with filter for $30. I was about to try some Pennzoil Ultra until I saw German Castrol on sale.

 

Given this info, there's now a part 2 to the question. I change the oil every 7.5-8.5k miles but change the filter (Pure One or Bosch of late) midway thru the life cycle of the oil. The oil comes out brown-- not lite brown and not dark brown, at 8.5K miles.

Mobil 1, Castrol Edge, Amsoil and maybe 1-2 other synthetics claim 15-25k miles miles between changes with no harm to the engine (in normal use). At 8.5K mile between changes with a filter change at 4K, will PP or RP or any other synthetic run for this distance even if an extended performance claim has not been made--- or are the formulas in these claimed extended performance oils such that they will outlive, for example, Penz Platinum?

One of my points is that the greatest wear on your engine may actually occur immediately after an oil change when the fresh oil has to run thru the new filter, which can take an extra 2-3 seconds (I'm assuming this, I'm not a mechanic, I'm a shrink). Thus, I try to run a longer interval between changes.

Thanks again for everyone's thoughtful answer, very much appreciated.

 

If you want to run your oil that long, you'd had better get an UOA. Just because the oil can go that long doesn't mean your motor is in good enough health to do so. Mobil 1 only has their extended drain option to run longer intervals. Amsoil has a pretty stout additive package designed to run long intervals. Make sure you run their best versions.

The wear that the motor might get after the oil change is insignficant if that. I try to fill the filter as much as I can before putting a new one on

 

^Why don't you just send in a UOA with some of the oil from your 4k filter change and then again from your 8k filter change... the people that do the UOA can tell you if the oil is holding up or not.

 

I have no problem running a good quality oil for 8K. PROVIDED that 90% of your driving is highway for at least 30 minutes at a time. I did almost 100% in my old company truck. I changed the oil ever 3K and EVERY time the oil guys would say; "why are you changing this, it looks brand new". What hurts oil (and engines) is NOT WARMING COMPLETELY UP (at least 30 min of highway) stop and go driving, idling, NOT high speed long distance running. If you do nothing but city type stop and go, I would change at 3K no matter what.