As long as the car spent its first 25k or so on regular before switching to synthetic, you can switch back no problem. Most likely the original owner did regular since that's what they put in it from the factory at the time so you shouldn't have any issues. However, on newer cars that use synthetic from the factory, it's not such a good idea from what I've heard. I'm pretty sure no Series II 3800s ever used synthetic from the factory. When I rebuild the motor in the Camaro I'll probably switch to synthetic at that point. I just don't want to take the chance of old cork gaskets still being in there at this point since synthetic WILL eat those away. That's not an issue on any of the EFI motors to my knowledge though.

 

It's a judgement call on your part. You can run synthetic longer, but the greater benefit is that it doesn't break down as easily as dino oil so it offers better protection and (as mentioned) does a better job keeping your engine clean. Getting every last drop of dino oil out before putting the synthetic in is not critical. They are 100% compatible with one another.

 

That's actually a myth. The synthetic will not cause a cork gasket to deteriorate. What happens is the synthetic oil cleans the sludge away that was preventing the dino oil from leaking. Leakage is a very rare occurance though and is usually only seen on very high mileage engines that didn't follow a regular oil change interval.

 

And if you're going to buy a synthetic, make sure you're really buying a synthetic. Anyone who tells you that synthetic oils are just highly refined or refined differently, but still use base oil, they're lying to you.... Valvoline has this crap on their own website... and the Federal Government ruled that they can still call it synthetic.

Synthetic oils are 100% lab grown. Usually a polymer base, like Royal Purple, and there is another base that is common, and I think Mobil 1 uses that.


Semi-synthetic is just crap... they imply it's half-half, but as posted, it's not.


And all these rumors about "Once you switch synthetic, yo ucan't switch back" I believe were started by teh organic oil companies to keep you scared. You can pour two quarts of organic and three courts of synthetic in your car and it will run a long, happy 4-5000 miles or so. Heck I've run 8,000 miles on synthetic between changes (just don't cheap out on a filter if your'e going to do this), 130,000 miles on that Monte of mine. I ain't skered.

The rumors of "synthetic oil causes leaks" are a load of it too. It's kind of the same argument that came along in the 40s and 50s. Synthetic oil has a much more consistent molecular chain, and those molecules are smaller than organic oil molecules. They can find smaller holes. If you rebuild an engine and only used synthetic oils in it, the seals woudl actually last longer than if you used organic oil.

Back in the 40s and 50s, detergent oils came along. Prior to this ,about all you had were 30, 40, and 50 "weight" (there were no multi grade 10W30's and the such at that time), oils with no detergent. Well people poured detergent 30 oil in their cars, and it started leaking like Niagara. So everyone started saying, "Oh, these detergent oils cause leaks, they're not worth a !#@(%!%!&#%#!(%&!%!%!#%!# and I won't buy one of these (!#&%!(%)@#!%# ever again." There are still some old tractor guys to this very day who won't pour anything but 30 "weight" (for lack of a better word) in their tractor because "anything else will cause a leak." Teh reality was, the detergent oil cleaned out sludge that was stopping up leaks anywho.


I wouldn't let the type of oil run by a previous owner be the deciding factor in my vehicle purchase. Unless they ran 50W non detergent oil.

 

Even on regular oil I still follow the intervals in the owners manuals in my vehicles (which all state more than 3,000 miles, 4500 in the truck and I think closer to 5-6k in the Camaro). The whole 3,000 miles deal was started by those quick lube places based off the harsh driving section of the owner's manuals. I just changed the oil in the truck after about 5k and the oil actually looked relatively decent. I'm probably around 5500 miles since the last oil change in the Camaro and the oil still looks good. I'll probably change it pretty soon though when I have some extra time to run it down to Redstone.

 

The appearance of oil can be a bit misleading. Even though it may look okay (clean) it's the viscosity index, friction modifers, rust inhibitors, EP additives, detergents, etc. that wear out and lessen the oil's ability to protect. Best bet for determining oil change intervals is to have your oil analyzed. Most major oil companies have found that the deterioration of these additives begins around 4,000 miles for the 'average' driver.

 

If you really want to know, you can keep your old oil and send it off to get evaluated.

They will tell you how much it is breaking down, how much metal is in it, etc. etc.

 

SO does anyone think it'd be worth it in a car that gets lets just make a high guess since I havent had a lot off time to drive it say 5,000 miles a year and is stored in the winter months of say end of november/early decmeber to late april/late may (depending on the winter). I know it costs more but to mean if it means longer life of and engine then it'd be worth it. Just still debating.

 

The less a car is driven like that, the more the synthetic benefits the engine (since the car sees more periods of time just sitting).

 

You can tell a lot from a paper napkin. That being said, I still follow the owner's manual within 500 miles or so. And the manual for the Camaro says nothing about 3-4,000 miles LOL.