Somehow I just stumbled on it and read through. I understand that 99% of people are steadfastly in one camp or the other, with zero chance of anyone changing their attitudes about the dino/synth question. Just the same, I'd like to give my .02 ...
Until retiring three years ago I was an Abrams Tank mechanic in the Army. I maintained a wide variety of vehicles, though. Anything assigned, whether tracked or wheeled. During my 20 years (active, not a weekender), the rules on oil service varied about zero. Oil life was measured only by an oil analysis, and was changed only when:
1) a sudden change in wear metals or contaminants was detected, or
2) a certain threshold of concentration of contaminants/wear metals was reached, or
3) the oil had to be drained to perform other repairs.
Sometimes, we'd get a notice to change only the filter and re-sample immediately or after some predetermined period of operation.
Sometimes we'd get a notice to cut the next sampling period in half. Analysis results were generally only reported back to us if they were bad, but we could obtain a roll-up report for all our assigned vehicles.
For a little while when I was but a young Soldier, it was my job to also drive our motor sergeant's HMMWV. It being my baby, I really wanted to look after it, so one time I serviced it out of schedule and filled with Mobil 1 I had at home. The lab flagged the next sample because of the change and I had to fess up to what I'd done. My shop foreman had a good relationship with the folks over at the lab so we didn't change it back to the approved oil. He kept tabs on the analysis results on my truck, and a couple years later we still hadn't changed the oil in it. Meanwhile, the remainder of our wheels all had to have oil changes. That was enough evidence for me to know that a synthetic was better.
I'm sure most guys have peered into the area under their oil cap. On most vehicles I've looked into it's never been anywhere near clean. I recall one friend who was a lifetime penzoil fan because his daddy told him so. His camaro got so full of crud that he wound up with a really bad oil leak from the valve cover on one bank. He changed the valve cover gasket a couple of times before he decided to ask around. We determined he had clogged drain passages, causing oil to fill the area around his valve train. Once sufficiently full it would push out the gasket. We pulled him into the bay and pulled the valve cover, and used a power drill and heavy wire to "drill out" the crusty garbage. He switched to synthetic and after a few oil changes pulled the valve covers because he got some shiny new chromed covers that were good for at least as much HP as the stickers on his windows. I didn't see with my own eyes, but he reported that the built-up deposits he'd grew up thinking were normal just weren't there anymore. I think he was a lifetime convert after that.
For a few years I enjoyed chasing (and killing) cones on the weekend. Like most autocrossers I ran what I had, which for me was a 96 Monte Carlo Z34. It was a heavy, underpowered, ill-performing beast of a FWD car. I bought it with about 36KMi on the clock, but fed it only synth the whole while I had it. One time I took my neighbor's son with me to an event about 150 miles away. I discovered I had a blown head gasket after my first angry lap that day, and didn't bat an eye. He co-drove with me and we put 16 or so good runs on it before packing up at the end of the day and heading home. We got within 40 miles of home and had to stop because there was litterally no coolant left. We pulled into a Hooters, ordered beers and food, and called a tow. It was so hot when we stopped that the cooling fans ran the battery completely down. Keyless entry, courtesy lights, nothing. It was still pretty frickin' hot when the tow showed up. He hauled it home for me, and I did the repairs in my garage at home. By then it had about 100K miles on it. The heads were still planar, and I only replaced gaskets. I continued racing the car after that, even winning a touring series championship with it in a class that was dominated by the Subaru WRX. After the championship win I moved to a more proper sports car (an S2000) and sold it to another friend's son within spitting distance of 200K miles. Two years later it developed an oil leak due to a bad o-ring on the pil pump drive (imagine just the bottom half of a distributor). That repair required pulling the front cyl head to be able to remove the drive. My friend (the buyer's dad), has been a mechanic longer than I've been alive (I'm now 40), and could not believe I didn't rebuild the engine before I sold it. The cylinder walls were pristine, still bearing honing marks. The cam carriers, valvetrain, cyl heads, etc were clean as a whistle. He wondered how the engine was so clean, and so apparently fresh looking, with so many miles. I told him I'd fed it only synthetics since I bought it. He is a lifetime convert now, as well.
I admit that is a little more than $.02 worth of post, but I have had nothing but excellent experience with synthetic lubricants. Before I was a synthetic user I'd had rod bearings spin due to oil starvation. I'd had a small engine seize when overheated and barely low on oil. On synthetics I've seen a double-gasketed oil filter spill all the oil out and the engine run on zero oil pressure a mile to a gas station, but suffer no consequences.
The way I see it you can surely get by using conventional motor oils if you're careful to change them with some form of regularity and you don't really abuse the engine. When you do require repairs it may cost you a little more, but you'll have saved a little money buying cheap oil so you might not mind. If you are prone to abusing an engine, or are not so careful to mind some sort of service schedule, then synthetics are definitely for you. Also, if you've already spent the 10% money to get 90% of the available power improvements, and the 90% money to get that last %10 in improvements, then you might as well not throw it all away on even a momentary oiling problem.
I change engine oil annually because I'm too forgetful or lazy to mess with oil analysis. I rarely go over 15K miles in a year. Wally-world sells 5qt jugs of M1 5W-30 for less than $30 all the time, and a couple decent filters a year (one mid-year, one at oil change) puts you in for what, $60/year? That's damn cheap insurance to me, and I KNOW my oil is good, whether I just poured it in or it's been in there six months.
I'll admit I'm a bit of a cheap bastard, but feeding your engine anything less than a high-quality synthetic is just foolish.
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