@kkritsilas said "
The viscosity testing is set by the SAE. There is no difference between a conventional oil rated SN, and a full synthetic rated SN. The 10W30 is the same viscosity whether it is synthetic or conventional. Synthetic is actually slipperier, for want of a better word, than conventional oil. However all that being said, you use the grade specified by the factory. When both synthetic and conventional oil were being used, there was NO factory manual that ever suggested that a different viscosity oil be used when using synthetic vs. conventional. The factory determines what grade to use, not the oil manufacturer or distributor. The factory designs engine tolerances and clearances, not Amsoil. Redline, or any other oil manufacturer or distributor. When the factory says use 10W30, 5W20, or 10W40, use what they say. We can change those tolerances by rebuilding with tighter or looser tolerances, and you builder should recommend a grade or a brand. that is with full knowledge of what those tolerances are.
Our LA engines were built with tolerances designed for use with 10W30, or 10W40. The Magnums were built with tighter tolerances, so probably use a 5W30. However, using a 0W20 in an LA is taking an unacceptable risk in my mind, not even considering that the tolerances on our older engines have opened up even further."
I agree with what he said, 100%.
I've not tested oil vs. oil myself nor plan on it. I have worked on a thousand of Chryslers, many of which are high mileage car, over the years.
What I can tell when a person changes his oil every 3 to 5,000 miles vs. who changes it every couple of years or so. Being a mechanic, I don’t get to ask the customers which oil was used or for how often.
Also, I really really dislike working on "sludge bucket" engines . . .
On two (possibly) unrelated issues:
One - When an item (any item) changes temperature and the humidity is at a certain percentage, water will condense on the outside (or inside) of that object, and that includes automobile engines. A cold drink on a hot day is a good example of this. Any water (or moisture) that makes it way inside of an engine will boil-out over time when engine is in operation.
On ‘70/80’s Chrysler engines, this process takes about eight non-stop driven miles to accomplish. Any less than that, regardless of brand of oil used, will cause the formation of sludge inside of the engine over time from not getting that water moisture completely removed.
The shorter distances driven, the faster and greater amount the sludge accumulates.
Example, if a person drives say five miles to work and back, I would recommend making one of trips/legs about three miles longer so one direction is eight miles and the other leg can be five miles – to avoid sludge forming.
If you already drive car eight miles (or more) when car is driven – then great (you get a pat on the back)!
Item two. I have always heard that engine gaskets shrink over time. That said, I have replaced hundreds (thousands maybe) of engine/transmission gaskets over the years and not thought twice about it. When I purchased my ’77 318 wagon a few years back, the car was an all original car with 32k (or 34k) miles on it. Within a short time of driving it, every single gasket started to leak on the car (engine, transmission, P/S, etc.). I had to retighten every (accessible) bolt about ½ to a full turn until bolts were tight (torqued). The front pump gasket bolts are also loose (leaking) – but that requires a bit more work to access. This car has proven to me that gaskets will shrink over time.
My opinion as to oil:
- On a high mileage engine or an engine that is consuming oil, I think
any (correct weight) oil with a decent detergent rating, like SH to SN will work fine. The higher the second letter (SN, for example) means the more detergent in oil which helps keep inside cleaner. If engine is burning, say, a quart of oil every 500 miles, expensive oil can get very expensive . . . quick.
- On a fresh rebuild or an engine a person has a lot of money in, then by all means get out the good stuff and change it often.
- Those cars in-between those two (mentioned above examples), the induvial owner will need to that decide themselves.
Personally, when I get oil for my vehicles (’10 Town and Country (w/200k miles), ’77 Wagon (w/50k miles), or ’86 Fifth Ave (w/90k miles)) I purchase the oil when on sale (generally the cheap stuff, but with a SN detergent rating), and change it every six months (about 4-6k miles), which is every April and every October. My diesel pickup (230k miles) has different oil requirements – but I also change oil in it every six months (all three gallons of it).
If you ever get a chance to drain engine oil from a car that has sat (untouched, but hood closed) outside for a few years (engine not locked up but not cranked in many many moons), you will find, in most cases, a good bit of water will be in the drained oil, at the bottom (about 1/4 inch deep or more). The water that is present because of moisture condensed due to normal temperature changes. Sense oil is lighter than water (even 50w engine oil), the water will go to bottom and can’t evaporate. Pretty much all car manufactures say to change oil in a mileage OR time interval (usually 12 months) – for this very reason.
I’m neither pro/con synthetic or pro/con any specific oil manufacturer.
I am very pro on changing oil often and very pro on driving car at least eight miles on any one leg every day the vehicle is driven. Other than that, I don’t want to get into arguments about the other details.
Note: we change oil because of dirt/contamination (which also includes water and/or sludge) and not because the oil breaks down (in most cases). A oil filter captures most dirt/contamination but only down to a certain micron size (usually 5-20 micron size). The dirt/ contamination smaller than that will still wear an engine and can’t be captured effectively. If a person could find a cost and size effective filter to capture dirt or other contaminates smaller than that, then I would all for letting engine oil go for a longer distance (like say 15-20,000 miles).
dirt/contamination is the enemy of engines, not the oil. The oil is what transports the dirt/contamination around to the different bearing surfaces.
BudW