Okay here I go again. Grab a seat.
There are several thing to consider with motor oil. First is the viscosity rating. 10W30 is original in a C3, and I recommend sticking to that. Any engine is designed to specfic clearance. The oil must be thick enough to take up that space. If it does not, the metal will clash. This can be done using a thin oil, say a newer 5W20 or 0W20. Newer engines have tighter tollerances and require this thiner oil.
Some folks like to use 20W50 racing oil. NO! Racing engines are build with much larger clearance gaps. This is so the expansion from heat will prevent the engine from locking up. Very thick oil designed to do this works great in those engines, but is too thick to flow into the smaller spaces in a normal engine. While this creates great oil pressure due resistance of flow, it actually starves the bearings and such from getting enough oil. As the engine wears out and gets sloppy, the oil now works, but the engine is 1/2 or better worn out. Not good.
Just as pushing or dragging a box across the ground or sand, material will build up in front of the box instead of just going under. What does go under gets jambed in place, and causes a pressure increase. Same thing happens in the engine. Oil get pushed into the bearing and friction surfaces, and gets wedged in place, (yes it's flowing). The hydrostatic pressure greatly increased the oil pressure. You can develop over 5000 pounds of pressure in the bearings. Oil too thin can not hold the oil film, and metal strikes metal. Oil too thick does not flow in well, starves the bearing, and the volume of oil cannot build the hydrostatic pressure. Again metal strikes metal.
Next, general quality of oil has improved over the years. Modern engines last longer for two reasons. Generally the are machined better. But newer oils provide much better protection for the engine. Most of the older, lesser oils have been replaced and are not longer available. No worries there unless you have something sitting your garage or warehouse for the last 15 or 20 years.
There is also the letter rating. If you require a SE engine you can use an SF. Both of these are older and you probably won't find them. What ever your engine calls for can be replace by a letter further along, but you cannot go back. The further you go down the 26 letters, the better.
Now comes a sneaky one. Oil has a combination of zinc and phosphoresce. This is known as the oil's phos rating. Older oils had a rating of 800 to 1200. The EPA did not like this due to the heavy metals escaping into the world, creating some pollution. Newer oils are limited to between 200 and 400 phos.
So what? Well if you have roller lifters and camshafts we don't care. But a flat tappet lifter and cam is a different story. The highest pressure point in an engine with a flat tappet is the cam tip and tappet. This requires a high pressure lube, thus a high phos oil. The phos IS the high pressure lube.
On fairly new engines with a flat tappet, the newer low phos oils will cause the tappets, lifters, and cam lobes to rip apart. If the engine has over 50,000 miles the metal gets impregneted with the high phos, and the new low phos oil is not a problem. But if there is not enough phos in the metal, it's a sure fire failure.
When you go to the parts store you can find a high phos subsitute. This is usually in a quart of unknown oil. I don't like the quart of unknown oil. What oil is it anyway? What's it's rating? You can also buy a smaller quantity of additive. Far less unknown oil. Both are expensive. For the time being I still have couple of cases of Exxon Superflow in my garage. Good old high phos oil. But try to find it now. One day I will run out.
When that day comes with less than 5000 miles on my flat tappet cam, and not wanting to use an unknown lube, I go to plan B.
Easy really. Get a 4 or 5 dollar bottle of high pressure engine assembly lube. Mosts parts stores have it in stock. It comes in a 4 oz bottle and is enough to put together an engine, and keep it lubed during startup. This also kicks the phos rating WAY up. Great for new engine break in.
Just put 1/2 a bottle, 2 oz, of engine assembly lube in with an oil change. Instant high phos oil. No unknown lubes. No stupid high prices. Just great engine protection. Of course if you have a roller cam you don't have to worry about it, no matter the age or design of the rest of the engine.
Standard oil or synthetic? Well really, synthetic is better. Do you need it? Depends on your driving and engine. Oil does not wear out. The additives do. The additives make the oil what it is, so they are very important. Oil also gets contaminated. The only way to get rid of that is to change the oil. With some synthetics you can have an analysis done to determing the amount and type of wear in the engine. Very cool. But it's not cheap. In most cars it's cheaper to change the oil than analyize it. Some vehicles, trucks, that use very large quanties will do the analysis, restore the additives, and change the filters and keep driving. At some point it has to be changed, but the engine may go through several regular change intervals before that happens.
So you have to change it anyway. That does not mean you don't want the better synthetics, but if your engine is worn or using excessive oil you are probably wasting your money.
It has been said that you can't mix regular oil and synthetic. Really? You can buy a blend in the store. Get over that one. Does mixing in regular reduce the overall quality? Of course. But if the regular oil is a good quality, that's not automatically a bad thing. If you need protection at a level 4 and you are using a 7, a 10 may not be better for you, but it sure won't hurt either.
In some cases switching to synthetic will cause the engine to burn oil and/or leak like crazy. This is due to the better oil cleaning all the gunk out of the seals, gaskets, rings, etc. Switching back to regular oil will not fix this. The sealing goop is gone. Now you have to reseal and/or do the repairs to stop the problem. The flip side is if the engine had proper oil changes and service in the past, that crap wont be in there to begin with, and the switch is no problem at all.
Some newer engines, including the newer Corvettes, require synthetic oils. When it calls for synthetic, don't cheap out. The engine needs to to perform it's best and last longest.
No, I did not tell you a name brand. I do have my preferences, but the ratings are the most important thing. If you try two oils, and one of them makes it quieter, run smoother, and use less oil, stick with that oil. Or try oil number three and compare again. Oils well that ends well.
|UPDATED|8/11/2015 4:14:14 PM (AZT)|/UPDATED|
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