I think the topic says it all. I'm thinking about switching to synthetics and wonder how often they should be changed. Synthetics tend to be twice the price or more so in my opinion it should last twice as long or longer. I've heard every 6,000 miles... all the way up to 10,000 miles. Any opinion or documented proof on the answer to this question would be greatly appreciated.

 

Different people say different things...

The factory (GM) for instance calls out for a 3000 mile interval with dinosaur juice, and some much longer interval with synthetic. Interestingly enough, for the Vette (which has had Mobil1 in it from the factory for many years now) the interval for a 99 model is 3000 miles but for a 200 or newer it's something like 7500, with no change to the oil or the engine at all. Most of the mfrs. of synthetic claim about double the lifespan. My personal preference is to change it at about 5000-6000 miles. It usually is starting to look dirty by then anyway, full of combustion products and so forth. It still seems plenty slick, and about the same viscosity as ever, just contaminated.

I have no proof or documentation, that's strictly one man's opinion.

 

I change mine every 3k miles, but since at college I try to change it every 3months, because I only drive 25 miles a week and an occasional 400 mile round trip. The most important thing is to change it frequently, I wouldn't go out and buy synthetic just because you don't want to change the oil as often.

Oh, and I use Mobil 1.

 

I change mine every 3000 miles.

The one thing that most of the 10K changers can never understand is that the oil filter, filters out the solids, but does nothing to filter out the chemical contaminations from exhaust gases & other things. These contaminations can easily change the viscosity properties, and can make the oil acidic.

I know this sound like I repeating what 'RB83L69' said, but thats also my opinion.

Ron

 

I use mobil 1, and I try to change it at 3k every time.
With an older/ higher mileage engine, you should probably stick to the recomended 3k intervals. The higher mileage engines allow more exhaust gasses to enter the crankcase, thus contaminating the oil more than a newer (less wear) engine.
Whatever you use, I would change the oil and filter at 3k.

 

I use Mobil 1 and I change it at the end of each quarter, which turns out to be about every 11-13 weeks.

 

How many miles does that come out to be though. For someone who only drives back and forth through their own town to go to work and back would accumulate less miles than someone like me that drive 70 miles round trip to work 5 days a week. After calculating though I guess that's not too bad since in 11 weeks I would put on 3,850 miles just to work and back .... 13 weeks is 4,550. So I would be changing it half as often as I do now with regular blend oils which seems to be what a few people do anyhow. I think I'm going to post a poll.

 

I don't think you'll get too far with that poll!

 

Amsoil has 25,000 mile synthetic?
Good Oil but I dont dare