I know there have been multiple discussions about the 'best' kind of oil to use for our 4's & 6's, but I could use a little education on oils in general.

My daughter has a Chevy Trailblazer with 140k+ on the clock. She usually has one of her 'guy friends' change her oil because she doesn't trust the oil change shops and doesn't know what kind of oil they use.
Straight dino oil is getting hard to find and/or as expensive as synthetic. But I seem to recall from years ago that it was not a good idea to go from dino to synthetic without flushing out the entire engine. Still true?
And what about the 'blends'?

My DD uses synthetic and I just take it to the dealer/local shop for a change.

Words of wisdom are welcomed.

If its a chevy with 140k on the clock
Just put mobile 1 full synthetic in there
And tell your daughter that you will help teach her to do her own oil changes


"GUY FRIENDS "

Stay away ..... imho

I’ve been told that if an engine might be heading towards a leak, going synthetic will push it over the edge. But more recently, that they’ve addressed that and it shouldn’t happen.
I was skeptical so I was really worried when our youngest told me he had done the last two oil changes on his 944 with Mobil 1. No leaks so...

That is one of those myths that just won't die. You can add any motor oil to any existing motor oil. They even sell dino/synth blends.

The leaks in old motors concept sounds a bit more believable, since, as I was told, the synth oil molecules are smaller & slipperier than dino. This, too may be a myth.

My dad told me he thinks that myth is due to people associating dyno oils with non-detergent oils since the switch from a non-detergent to detergent oil could be really bad and dislodge a lot of stuff.

I've always run full synthetic in our DDs, but have more recently been using the full synthetics labeled for "high mileage" vehicles. We have a 1991 Pathfinder with 250K plus miles, and a 2006 CRV with 200K plus. Both going strong with very minimal issues over the years. I have no idea what is different about the "high mileage" oil, but it doesn't cost any more than other full synthetics.

I had heard the same story on synthetic.
The way it was described to me was, the new synthetic oils work on a smaller level. Think molecular. They are designed to penetrate into the metal and allow the lubrication at smaller scale. Think softball size to BB sized. If the seals have any cracks that are currently holding under the larger size, the new smaller material can seep out. I would't change if my engine was tired, but you may be able to get away with it if in't in pretty good shape.

So the story goes.

"High Mileage" oil has more conditioners added to the formula to keep seals pliable. You don't need to flush your motor and you can change whenever you like. In fact you can add synthetic oil to a motor that's running conventional (or vice versa), but you'll lose the benefits that synthetic oil has.

Thanks all. I think a lot of what she was concerned about revolved around the 'myths'. Bought enough dino oil to do this change, will probably go to high-mileage blend for the next one.

And I don't worry about her 'guy friends'. She's 5 ft/100 lbs, but her bedroom wall is decorated with pistol targets with lots of holes in the black rings. And her computer desktop picture is her in shorts and a bikini top shooting skeet with a 20 gauge semi-auto.

No interest in the 914 though....

Wish there were girls like that in los angeles