Thread: Oil change better every 10k miles with full synthetic, or 3k with conventional?

The title basically says it all, but all else being equal would you prefer to buy a car that had the oil changed every 10k miles or so with full synthetic, or would you prefer a vehicle that had the oil changed every 3k miles with conventional oil? Thoughts, and what are your reasons?

I used to think it was important... But like i have learned from a few other members on the Forum, Oil is oil. It will get dirty faster than the expectancy of 3k for conventional or 5k with synthetic. I used to do only synthetic on my car every 4-5k miles for 1.5 years until yesterday where i did a conventional oil change. As of lately i realized it honestly makes no difference. Even took it to the drag strip yesterday, Still felt confident on the conventional.

I wouldnt trust 10000 mile oil , no matter what the bottle says. 5000 on synthetic, 3-4000 on conventional

Listen to scotty... He knows whats up. He is one of the members I mentioned I learned from.

I am not sure I agree with the 'it is all the same' logic. Synthetic is proven to hold up better under high temperatures, it has more detergents, and oil does not break down as fast (among many other scientifically proven differences). But the technical specifications are a whole different topic.

I am not sure how you figure you save any money doing conventional changes more frequently. I guarantee this will cost you more. You are buying twice as much oil and twice as many filters (so unless you stock up all at once you can figure twice as many trips to the store), and spending twice as much time.

But all that aside, I was not wondering about oil change best practices on your own car, I am looking at purchasing one of 2 different vehicles. One has been serviced regularly at a local quick lube with Mobil 1 full synthetic at about 10k mile intervals (some closer to 6-8k, but looks like no more than 10k). The other was dealer serviced at more like 3-4k mile intervals using the bulk dealership conventional oil. Assuming all else was equal, which of these vehicles would you prefer to BUY, and why?

I'd go for the 3-4k mile car. Even if oil could last 10k the oil filter doesn't.

I agree oil change alone is far from the only thing to check, I just got thinking after comparing the two and wondering which is more preferable just on that aspect. Both have third-party (dealer and local quick lube) verified service histories. They both seem to have been taken care of for the most part. One has slightly more miles but a few more options. They both will need some service/maintenance/repairs, but I was just wondering on the engine alone which is more preferable. I run synthetic on all my cars, and I have personally seen where it makes a difference (one example is spilling some on an exhaust pipe--the synthetic will stay there a lot longer and will continue smoking a lot longer, and clearly has a higher tolerance to heat).

The point about the oil filter capacity is well taken too. I use high efficiency/high capacity oil filters that are designed to go the mileage I run. I doubt the vehicle with the full synthetic oil changes used a high capacity filter, it was probably just the standard filter off the shelf for that model (which is actually a fairly high capacity cartridge filter, but probably not designed for 10k miles...).

Mostly I was just thinking out loud about the comparisons of 3-4k mile changes of conventional vs. 8-10k miles on a full synthetic change. The one main thing holding me back from deciding between them is that the one with the full synthetic changes has about 83k miles on it and the guy seems real eager to get rid of it. Problem with that is that he usually keeps his cars for 150-200k+ miles until they literally don't go anymore, and now it seems he is wanting to get rid of this one rather quickly for a newer version of the same model with less miles. Just makes me wonder if there is a large repair looming...

My car has had two owners counting myself. It had Valvoline synthetic every 3k miles for the first 80k miles. At which point I bought it and used mobil one synthetic for the next 40k miles every 3k or less. When we opened her up to put the cam and change the lim gaskets last year it was immaculate. Looked completely brand new.

From what I understand, never ever buy a cheap fram filter. I stick to mobil/k&N filters myself. And never let it go more than 4k without an oil change. And I always use mobil-1. However I'm sure a cheap oil with a good filter and changed every 3k is just fine too.

Its going too many miles and using cheap filters that will burn you every time. I don't trust those high miles oils at all.

Cheapest stuff I can find in the GTP, usually wallyworld supertech special. I run it at 5-6k intervals and blackstone says I could probably extend it out to 7500 if I wanted.

I never understood the bible 3k mile oil change thing, that was standard for high tolerance clunky 60's cars with alot less sophisticated oil than we have today, of course it will last longer. FWIW my cylinders sitll have crosshatching on them and my valve covers have a some light brown staining, mostly from seepage I would imagine.