Synthetic blends are supposed to be good for vehicles that have old seals in them. Old seals tend to shrink when a full synth is used and cause oil leaks. They're supposed to offer the protection of full synth with the lack of leaks. Granted, this is at the expense of oil longevity.
However, if there is a high-mileage full synth it might have additives to counter this so it doesn't matter then.
My father had the opportunity to dyno his car once, and in between runs he changed the oil from regular 10w30( I believe) to Mobil1. I'll have to ask him again, but I remember it free'd up alot of power and the engine was cooler. I wanna say +10hp and -170F at the head...
I run dino Valvoline 10W30 in my car, just becuase I can get it super cheap and my car has about 135,000 miles on it, so I'll just stay with the dino.
I think smay665949 is talking about how now most "synthetics" are now made from dinosaur juice. There was a legal decision that it's ok to mark them synthetic just because they were very well refined, rather than having to manufacture them in a lab.
True synthetic oils are based on man-made hydrocarbons, commonly polyalphaolefin or PAO, but very few of the synthetic oils on the market are full PAO oils. Many of the oils allowed to be labeled as synthetic are in fact blends of processed mineral oil and PAO, or even just heavily processed natural crude oil.
That's a bit discouraging, much like the FDA ruling that high fructose corn syrup is "organic".
Regardless, the question becomes: Does it really matter in terms of longevity and performance?
Feel free to geek out over the pros and cons there. Credible evidence is lacking.
I've been doing oil analyses on my cars bikes and plane for the last ten years. I can say that for me, synthetics pay off in longer oil change intervals and smoothness. In my Mazda I'm changing the oil monthly sometimes simply due to the mileage I'm driving and doing it any sooner would be a pain. In 2001 I completed my Europa kitplane with a Rotax 914 turbo engine. In the process of trying to pinpoint a vibration problem using a very accurate electronic balancer setup we conducted a small test. I ran the engine the first twenty five hours on dino oil but was getting a barely felt resonance vibration either thru the prop or the reduction gearbox. We had the balance gear on the plane three times in one week, and got the prop and spinner assembly within a hair of perfect. At twenty five hours I changed the oil with Honda motorcycle full synthetic (before you ask why bike lube, the engine, gearbox, and slipper clutch all share oil and its Rotax recommended) and the resonance disappeared. I had the balancing guy come out once more and the equipment verified that it was no longer there. And before you assume this guy was some cherry, he does this on planes and helicopters for a living, balancing props, gearboxes, and rotor blades and he knows his business.
The oil analyses also verify that less wear is taking place inside the engines and transmissions.
My Mazdaspeed 3 supposedly came with synthetic in the transaxle but I changed it to Royal Purple synthetic at 14k and both cold and hot shifting improved.
Me? I'll use nothing else.
Ignorance is lack of knowing; stupidity is false logic
If they are not pure synthetic however, it should say "blend" somewhere on the label.
I looked at several of the syn "blend"brands to see what they said as far as the actual mixture and couldn't find it on the bottle. So I was wondering exactly how much syn was in the mix. Could be 10%......could be 50%.....I don't know. I would think that a syn blend would be a 50-50 mix but if they don't say then it makes me wonder. So I just use full syn.