I just use blend, but Id suggest going with 5w30 or 10w30 stock tune if you plan on keeping it terribly long.
Here we go again....thinking that you "KNOW" better than the people who designed the product.....here's some reading to think about...
Thick Oil? Thin Oil? Right Oil!
Written by Pat Goss
In preventive maintenance nothing is as hotly debated, universally misunderstood, or improperly used as oil. Hereās a typical oil discussion, āthicker oil is always betterā - āno way, thinner is betterā - āitās daylightā - āno itās darkā - āwho cares, oil is oil.ā All from two basic groups: the know-it-alls and the know-nothings.*
Know-it-alls may have been messing with oil for years, plus they acquire knowledge from generational rituals of passage. Whoa, reality check! Their oil knowledge is probably more myth than substance. Handling oil does not make anyone an oil expert! On the other hand, know-nothings just go along with the program. āAfter all, oil is oil so whatās the big deal? All this talk about viscosity makes me crazy.ā*
How much do you know about oil? Are you convinced that thinner oils are only recommended for better fuel economy ratings? Do you believe thicker oils are better than thinner oils? Or, oil is just oil? Actually thereās much to learn about todayās engines and the oils that protect them; for instance, thicker is not better and oil is not just oil.*
Old lies die hard. The notion that thicker oil is better never was true but āback in the dayā it was usually harmless. Be careful, it isnāt harmless anymore and to understand why, you have to understand the oil-to-engine relationship. First and foremost oil has to lubricate moving parts and to do that it must circulate between those parts. Looking at the inside of an engine it appears that metal touches metal, but it doesnāt. Touching would be deadly.*
The moving parts inside engines are separated by tiny gaps continuously filled with oil. So, rather than riding on, or against one another, engine parts move on a thin film of oil. If the oil film goes away due to inadequate āshear strengthā or improper thickness, engine damage occurs in seconds.
Oil thickness (viscosity) is vital to engine protection. Oil viscosity recommendations are based on a number of factors, but one of the most critical is the clearance between moving parts. Before the age of computer-controlled machining tools there was a lot of space or uneven spaces between parts. But new computer-controlled machines create parts that fit like the parts in a fine watch. This is about ten times more precise than machined parts of 20 years ago.
Hereās the rule. Oil must fill the space between moving parts yet be able to circulate freely. With smaller, more precise spaces between parts, thinner oils do a better job of flowing freely through the engine while still filling the spaces. Thick oils can fill bigger gaps. That was desirable years ago when the gaps between parts were bigger, but big gaps are history. Thick oil without big gaps disrupts two flow characteristics, oil pressure and oil-flow volume.
Thick oil is tricky stuff! It can fool you into thinking it is better because it increases oil pressure. Higher oil pressure by itself is a good thing, but when it comes at the expense of oil-flow volume, itās bad. Thicker oil is harder to push through the spaces between parts. This makes the oil pump work harder, which in turn increases oil pressure, but simultaneously decreases oil volume.
Pressure-volume experiment: remove your garden hose nozzle, open the wall spigot and observe the stream of water. The stream will be big (high volume) but wonāt go very far from the hose (low pressure). This is similar to oil in your engine when everything is working properly.
You canāt make water thicker so to get the same effect (as thick oil), itās necessary to restrict water flow. Place your thumb over the hose opening, which significantly increases water pressure making the stream travel much farther. Although the pressure is greatly increased, the volume is greatly decreased. This is what happens when you use thicker than recommended oil in an engine; pressure goes up, volume goes down.
Too thick oil, wonderful oil pressure, yet parts inside the engine could actually be starved for oil due to lowered volume. Another downer, circulating oil accounts for nearly 50% of engine cooling, so reduced oil-flow reduces cooling causing lubricated parts to operate at higher temperatures. Higher parts temperatures, more wear.
Too thick or too thin oils can both be bad for engines, but damage is neither immediate nor catastrophic; it just reduces overall engine life. Consider that using improper oil could reduce engine life by a conservative ten thousand miles. At a value of fifty cents per driven mile, in a one-hundred-car-fleet, that would be a loss of one million miles for a value loss of five million dollars.
Always use the oil recommended by the engine manufacturer. Believe it or not, you donāt know more about oils than the people who designed and built the engine.