Oil

No it doesn't. In my opinion and experience, the "3,000 miles or three months" for motor oil is along the same lines as "lather, rinse, repeat" for shampoo.

If you have a reasonably new car, do yourself a big favor and switch to Mobil 1 full synthetic 5w-30 and change your oil at 6000 mile intervals. The oil changes per change may cost about twice as much, but overall the cost will be the same or less than using conventional oils at 3000 mile intervals, and the protection provided to your engine will be far superior.

Actually the problem is that the oil will only hold so much in the way of contaminants and the filter can only remove so much. After a while the filter fills up and no longer filters adequately. Check the color. Note that after 3 months, especially of hard driving, it's not clean anymore and therefore isn't doing its primary job as well, i.e. lubricating the engine.

Years ago they only recommended changing the filter with every OTHER oil change. Some cars had basically no real oil filter, e.g. Volkswagen Beetle.

Charles of Schaumburg

What exactly would you define "hard driving" as? Long highway trip with no stop, or in town traffic with many stops? I would have thought the first one, but I would love to be sure about that.

Actually stop and go driving is actually harder on oil than steady highway driving. The oil never warms up properly or gets fully pushed through the engine at running pressure and temperature.

Charles of Schaumburg

I think it was "Reasoned Insanity" who stated:

Uh, no. Sustained long distance driving is easy on a car; it's the stop and go driving that puts high demands on the engine and everything else. Especially many short trips where the vehicle doesn't get the chance to warm up all the way to operating temperatures.

-Don

Thanks, that's what I was thinking. Add one more advantage to road trips over in town trips.

Or get time to push it all the way through all the little nooks and crannies that it does when it gets driven a long way and warms up.

Charles of Schaumburg

Why three months? If that is better than six months then obviously three weeks will be better still. I recomend every third day to minimise contamination, acid and sludge. With Mobil1 of course.

Huw

Yes, definitely Mobil 1. Much better than that crap Castrol that the Brits try to peddle in the US as real synthetic, when everyone knows it is a fake and a fraud.

Oh yes, you would have to change that stuff at least daily, ideally three times daily, just like common mineral oil.

Huw

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What about regular Castrol? Is that stuff good, if not the synthetic Castrol? I've had regular Castrol in my previous car before.

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This brings up another question. Who makes the best quality gasoline? Is the best gasoline at Break Time, Shell, Phillips 66, or elsewhere?

I want to get Toyota brand gasoline! ;-) [chuckle]

Who makes the Toyota brand motor oil that the dealers use?

Mobil

It may be that Toyota branded motor oil that is sold in the parts department is from Mobil, but that changes from time to time.

However, if you get an oil change at a Toyota dealer, the odds of them using Toyota branded oil are slim. Most of them buy oil in bulk from various suppliers like Pennzoil/Quaker State (now owned by Shell), Castrol (now owned by BP), Valvoline (Ashland), etc. If you want a full synthetic, most will use Mobil 1.