In response to your original question, full synthetic base oils are more oxidation stable (longer running) and have better inherent detergency (cleaner engines).
I cannot speak for the person to whom you are referring, but I can only guess they are speaking to the economic's of the issue. Since synthetics are 3-5 times the cost of the petros (dinos), that person may have been saying that it is not economically beneficial to change oils in less than 5 k intervals.
If you have the income to change synthetic oils at less than 5k, then that's your decision, but for the average motorist, it may not be economically beneficial.
The benefits in addition to longer drain intervals is its ability to function better at very high and low temperature extremes. It will not thin out as much at high temperatures nor thicken as much at low ones. This is partly due to better viscosity indexes of PAO. But aside from that, it doesn't appear to much better (if any) when looking at wear metals in oil analysis.
I use syn because it gives me added piece of mind (maybe wrongly so) if the engine somehow looses its cooling system. I've already told my wife and daughter if they are out on the road and warning lights come on-rather than pull over and put themselves at risk drive the vehicle to a safe place and screw the lights. Could be costly for me some day
IMO that statement of 5k for dino's cannot hold true on some motors and many driving conditions. Some with 3 quart capacities during Southern summers will simply eat up some dinos imo if the conditions are just right.
I like the synlubes because of the broad range of protection they offer from extreme cold to extreme heat. Depending on where these dinos are bought the prices are sneaking towards 2 bucks a quart if not purchased in the economy 5 quart containers.
Enter the neat Synthetic Blends which the true PAO blends are few and far between but they offer great cold weather performance and hot weather protection against oxidation at mid cost levels and a couple to include Schaeffers will rival the synlubes in cost VS performance while helping keeping the engine free of deposits.
Even a full synlube can and will sludge given the right conditions. One would be a heavy wt in winter and this comes from another source than dragboat.
There are many oils to choose from for you and your driving style and this site and it's used analysis section along with the collective member input is a great place to find the oil thats right for you.
Dragboat, please pardon my ignorance but what are the 'synlubes' you refer to? You mention their price as being upwards of two bucks a quart if not purchased in jugs. I know that you know your stuff. Thank you. krholm.
Mr KRHOLM good to see you posting again !
I beleive you misunderstood the pricing and product. Here is is what I posted:
"Depending on where these dinos are bought the prices are sneaking towards 2 bucks a quart if not purchased in the economy 5 quart containers"
Again it depends where the oil is bought. But Autozone's price is I think 1.79 per quart of Castrol dino.
The context of the reply to which I refer is a mixed one. In the first place, the member was commenting on an oil analysis done at 3000 miles (with favorable numbers). He noted that the results were not unexpected for that interval.
He then went on to say that there is an ordinary dino oil at just over $1/quart that would deliver similar numbers at that mileage.
What really prompted my question was his closing comment:
"if you want to really test an oil, you should stretch it out farther. I don't see much use in going with a synthetic and then leaving it in for less than 5,000 miles."
It appears that economics is principal consideration, but there is the testing--as in challenging the oil--angle, as well.
Would agree tat synthetic base oils as a class have greater oxidative and thermal stabilities than petroleum base oils. However, I have seen little evidence that they have greater detergency characteristics than their petroleum counterparts. For one, the PAOs would in my opinion have very poor detergency characteristics when compared to petroleum oils from the standpoint of their paraffinic chemical structure and absence of any aromatic hydrocarbons. Now, the polyols and esters would have better solvency properties than petroleum, but I would not view solvency as a component of detergency.
I somewhat believe that if you're doing 3k intervals in a moderate climate (not too hot, not too cold) and don't drive very hard, that you'll see identical engine wear numbers using a conventional oil compared to a synthetic.
Synthetics main benefits come with the ability for better flow in extreme cold and the ability to last for longer intervals. They also won't thin out as easily in the long run.
Also, most people I know end up trading their cars in long before they'd ever reach high enough mileage to need an engine rebuild, so from a practical and economical standpoint, the benefits of synthetics don't show up for a lot of people (especially those that continue to change the oil every 3k anyways)
I like synthetics not only for the fact that it gets down to 0F sometimes in the winter here, but also because I don't want to be changing the oil more often than I have to, since I take care of changing oil in 4 different cars (mine, my wife's, my mom's and my sister's)
I truly believe the synthetic vs dino oil argument will never truly be solved, not as long as there are people out there going 300k while using conventional oil. Try to convince these guys that they should've used synthetic! Not gonna happen!
Part of that protection includes some safety margin during bad events like engine overheating. Ever had a water pump or hose fail? If you don't want to drive on cooked oil, or you're afraid a spouse or child might not share your paranoia ("Oh, but a service station was only 10minutes away"), synth will keep working after hitting much higher temps than dino. Fairly cheap insurance.
I wouldn't use synthetics in a average car due to cost. Can't run it at a extended intervals without risking the warranty. If your owners manual says 7.5k or 10k oils changes use a synthetic for that interval. But not worth it for 3k. Unless you have a special type of engine.
I just bought a turbocharged car and these can be much harder on oil (heat). So I will run Mobil 1 at 5k intervals as that stretches it to my manuals (3k severe 5k normal) limit. When the warranty is about up I may have a oil sample done just to see how far it can go. German turbos go 10k on Mobil 1 all the time.
$2 to $2.50 per qt for syn blend with just 10% syn seems like a ripoff to me. The fine forum members here talked me out of mixing my own syn blend oil. Will only cost me about $5 more to run Mobil 1 at 5k compared to doing 2 dino changes at 2.5k each. Well worth the peace of mind.
As has been stated, the full synthetics also have have better low temperature characteristics.
"Now, the polyols and esters would have better solvency properties than petroleum, but I would not view solvency as a component of detergency."
Solvency is very important in keeping an engine clean; esters are the basis for the internal engine cleaners Auto-RX and Lubeguard.
Benefits of synthetics:
1) Better fuel efficiency - particularly with the 0w-30 and 5w-20 grades
2) Better protection from high temp engine deposits - PAO's and Esters thermally decompose more cleanly than do petroleum based oils. Several recent SAE papers document this effect ....
3) Better performance in very cold or very hot weather
4) Reduced oil consumption in mechanically sound engines, due to their lower evaporation rates
5) Reduced exhaust emissions, primarily due to #1 and #4
6) Increased biodegradability, due to the use of organic esters
7) Better piston ring seal, due to the higher film strength of the basestock
8) In two cycle engines ...elimination of exhaust smoke and spark plug fouling and the ability to run very lean mixture ratios of 100:1
You can get excellent wear rates with conventional petroleum oils and short - 3000-5000 - mile change intervals, so I have NOT listed that as an advantage of sylubes. However, in certain types of racing and severe service applications - pulling a heavy fifth wheel trailer for example - you will get lower wear rates with synthetics or synthetic blends like the Schaeffers Supreme 7000 series oils ....
If I sound biased - I am - due to 25 years of experience with synlubes in numerous applications